The COMMODORE 64, also known as the C64 or occasionally CBM 64 or
VIC-64 in Sweden, is an
8-bit home computer introduced in January
Commodore International (first shown at the Consumer
Electronics Show, in Las Vegas, January 7–10. 1982). It is listed
Guinness World Records as the highest-selling single computer
model of all time, with independent estimates placing the number sold
between 10 and 17 million units. Volume production started in early
1982, marketing in August for US$595 (equivalent to $1,477 in 2016).
Preceded by the
Commodore VIC-20 and
Commodore PET , the C64 took its
name from its 64 kilobytes (65,536 bytes ) of RAM. It had superior
sound and graphical specifications compared to other earlier systems
such as the
Apple II and
Atari 800 , with multi-color sprites and a
more advanced sound processor.
The C64 dominated the low-end computer market for most of the 1980s.
For a substantial period (1983–1986), the C64 had between 30% and
40% share of the US market and two million units sold per year,
outselling the IBM PC compatibles ,
Apple Inc. computers, and the
8-bit family of computers. Sam Tramiel, a later
and the son of Commodore's founder, said in a 1989 interview, "When I
was at Commodore we were building 400,000 C64s a month for a couple of
years." In the UK market, the C64 faced competition from the BBC
Micro and the
ZX Spectrum , but the C64 was still one of the two most
popular computers in the UK.
Part of the Commodore 64's success was its sale in regular retail
stores instead of only electronics and/or computer hobbyist specialty
stores. Commodore produced many of its parts in-house to control costs
, including custom integrated circuit chips from
MOS Technology . It
has been compared to the
Ford Model T
Ford Model T automobile for its role in
bringing a new technology to middle-class households via creative and
affordable mass-production. Approximately 10,000 commercial software
titles have been made for the
Commodore 64 including development
tools, office productivity applications, and video games . C64
emulators allow anyone with a modern computer, or a compatible video
game console , to run these programs today. The C64 is also credited
with popularizing the computer demoscene and is still used today by
some computer hobbyists . In 2011, 17 years after it was taken off
the market, research showed that brand recognition for the model was
still at 87%.
* 1 History
* 1.1 Market war
* 1.1.1 1982–1983
* 1.1.2 1984–1987
* 1.1.3 1988–1994
* 1.2 C64 family
* 1.2.1 Commodore MAX
* 1.2.2 Sx-64
* 1.2.3 Commodore C128
* 1.2.4 Commodore 64C
Commodore 64 Games System
* 1.3 Clones
* 1.4 Newer compatible hardware
* 1.5 Brand reuse
* 2.2 Alternative operating systems
* 2.3 Networking software
* 2.4 Online gaming
* 3 Hardware
* 3.1 CPU and memory
* 3.2 Joysticks, mice, and paddles
* 3.3 Graphics
* 3.4 Sound
* 3.5 Hardware revisions
* 3.5.1 ICs
* 3.7 Specifications
* 3.7.1 Internal hardware
* 3.7.2 Input/output (I/O) ports and power supply
* 3.7.3 Memory map
* 3.7.4 Peripherals
* 5 Reception
* 6 Emulators
* 7 See also
* 8 Notes
* 9 References
* 10 External links
Commodore 64 startup screen
In January 1981,
MOS Technology , Inc., Commodore's integrated
circuit design subsidiary, initiated a project to design the graphic
and audio chips for a next generation video game console . Design work
for the chips, named
MOS Technology VIC-II (Video Integrated Circuit
for graphics) and
MOS Technology SID (Sound Interface Device for
audio), was completed in November 1981. Commodore then began a game
console project that would use the new chips—called the _Ultimax_ or
Commodore MAX Machine _, engineered by Yash Terakura from
Commodore Japan. This project was eventually cancelled after just a
few machines were manufactured for the Japanese market. At the same
time, Robert "Bob" Russell (system programmer and architect on the
VIC-20 ) and Robert "Bob" Yannes (engineer of the SID) were critical
of the current product line-up at Commodore, which was a continuation
Commodore PET line aimed at business users. With the support of
Al Charpentier (engineer of the VIC-II) and Charles Winterble (manager
of MOS Technology), they proposed to Commodore CEO
Jack Tramiel a true
low-cost sequel to the VIC-20. Tramiel dictated that the machine
should have 64 KB of random-access memory (RAM). Although 64-Kbit
dynamic random-access memory (DRAM) chips cost over US$100 (equivalent
to $222.68 in 2016) at the time, he knew that
DRAM prices were
falling, and would drop to an acceptable level before full production
was reached. The team was able to quickly design the computer because,
unlike most other home-computer companies, Commodore had its own
semiconductor fab to produce test chips; because the fab was not
running at full capacity, development costs were part of existing
corporate overhead. The chips were complete by November, by which time
Charpentier, Winterble, and Tramiel had decided to proceed with the
new computer; the latter set a final deadline for the first weekend of
January, to coincide with the 1982
Consumer Electronics Show (CES).
The product was code named the VIC-40 as the successor to the popular
VIC-20 . The team that constructed it consisted of Yash Terakura,
Shiraz Shivji , Bob Russell, Bob Yannes and David A. Ziembicki. The
design, prototypes, and some sample software were finished in time for
the show, after the team had worked tirelessly over both Thanksgiving
Christmas weekends. The machine used the same case, same-sized
motherboard, and same
Commodore BASIC 2.0 in ROM as the VIC-20. BASIC
also served as the user interface shell and was available immediately
on startup at the READY prompt. When the product was to be presented,
the VIC-40 product was renamed C64. The C64 made an impressive debut
at the January 1982
Consumer Electronics Show , as recalled by
Production Engineer David A. Ziembicki: "All we saw at our booth were
Atari people with their mouths dropping open, saying, 'How can you do
that for $595?'" The answer was vertical integration ; due to
Commodore's ownership of
MOS Technology 's semiconductor fabrication
facilities, each C64 had an estimated production cost of US$135.
_ Game cartridges for
Radar Rat Race _ and _International Soccer
Commodore had a reputation for announcing products that never
appeared , so sought to quickly ship the C64. Production began in
spring 1982 and volume shipments began in August. The C64 faced a
wide range of competing home computers , but with a lower price and
more flexible hardware, it quickly outsold many of its competitors. In
the United States the greatest competitors were the
Atari 800, and the
Apple II . The
Atari 400 and 800 had been
designed to accommodate previously stringent FCC emissions
requirements and so were expensive to manufacture. The latest revision
in the aging
Apple II line, the Apple IIe, had higher-resolution
graphics modes than the C64. Though similar in specifications, the
two computers represented differing design philosophies; as an open
architecture system, upgrade capability for the
Apple II was granted
by internal expansion slots, whereas the C64's comparatively closed
architecture had only a single external
ROM cartridge port for bus
expansion. However, the
Apple II used its expansion slots for
interfacing to common peripherals like disk drives, printers, and
modems; the C64 had a variety of ports integrated into its motherboard
which were used for these purposes, usually leaving the cartridge port
free. Commodore's was not a completely closed system, however; the
company had published detailed specifications for most of their models
since the PET and
VIC-20 days, and the C64 was no exception. Initial
C64 sales were nonetheless relatively slow due to a lack of software,
reliability issues with early production models, and a shortage of
1541 disk drives, which also suffered rather severe reliability
issues. During 1983 however, a trickle of software turned into a flood
and sales began rapidly climbing, especially with price cuts from $600
to just $300.
Commodore sold the C64 not only through its network of authorized
dealers, but also through department stores, discount stores, toy
stores and college bookstores. The C64 had a built-in
RF modulator and
thus could be plugged into any television set. This allowed it (like
its predecessor, the VIC-20) to compete directly against video game
consoles such as the
Atari 2600 . Like the Apple IIe, the C64 can also
output a composite video signal (avoiding the RF modulator) that can
be plugged into a specialized monitor for a sharper picture. Unlike
the IIe, the C64's
NTSC output capability also includes separate
luminance/chroma signal output equivalent to (and electrically
S-Video , for connection to the Commodore 1702
monitor, providing even better video quality than a composite signal.
Aggressive pricing of the C64 is considered to have been a major
catalyst in the
North American video game crash of 1983 . In January
1983, Commodore offered a $100 rebate in the United States on the
purchase of a C64 to anyone that traded in another video game console
or computer. To take advantage of this rebate, some mail-order
dealers and retailers offered a
Timex Sinclair 1000 for as little as
$10 with purchase of a C64, so the consumer could send the TS1000 to
Commodore, collect the rebate, and pocket the difference; Timex
Corporation departed the computer market within a year. Commodore's
tactics soon led to a price war with the major home computer
manufacturers. The success of the
VIC-20 and C64 contributed
significantly to the exit from the field of
Texas Instruments and
other smaller competitors.
The price war with
Texas Instruments was seen as a personal battle
for Commodore president
Jack Tramiel . Commodore dropped the C64's
list price by $200 within two months after its release. In June 1983
the company lowered the price to $300, and some stores sold the
computer for $199. At one point, the company was selling as many C64s
as all computers sold by the rest of the industry combined, while TI
lost money by selling the 99/4A for $99. TI's subsequent demise in
the home computer industry in October 1983 was seen as revenge for
TI's tactics in the electronic calculator market in the mid-1970s,
when Commodore was almost bankrupted by TI.
All four machines had similar memory configurations which were
standard in 1982–83: 48 KB for the Apple II+ (upgraded within
months of C64's release to 64 KB with the Apple IIe) and 48 KB for the
Atari 800. At upwards of $1,200, the
Apple II was about twice as
expensive, while the
Atari 800 cost $899. One key to the C64's success
was Commodore's aggressive marketing tactics, and they were quick to
exploit the relative price/performance divisions between its
competitors with a series of television commercials after the C64's
launch in late 1982. The company also published detailed
documentation to help developers, while
Atari initially kept
technical information secret. The C64 was the only non-discontinued,
widely available home computer in late 1983, with more than 500,000
sold during the
Christmas season; because of production problems in
Atari's supply chain, by the start of 1984 "the
Commodore 64 largely
has market to itself right now"; _
The Washington Post _ reported.
By 1985, games were an estimated 60 to 70% of
Commodore 64 software.
At a mid-1984 conference of game developers and experts at Origins
Game Fair ,
Dan Bunten ,
Sid Meier ("the computer of choice right
now"), and a representative of
Avalon Hill all stated that they were
developing games for the C64 first as the most promising market.
Computer Gaming World _ stated in January 1985 that companies such as
Epyx that survived the video game crash did so because they "jumped on
the Commodore bandwagon early". 35% of SSI 's 1986 sales were for the
C64, ten percentage points higher than for the Apple II; the C64 was
even more important for other companies, which often found that more
than half the sales for a title ported to six platforms came from the
C64 version. That year _
Computer Gaming World _ published a survey of
ten game publishers which found that they planned to release
forty-three Commodore C64 games that year, compared to nineteen for
Atari and forty-eight for Apple II, and Alan Miller stated that
Accolade developed first for the C64 because "it will sell the most on
In Europe, the primary competitors to the C64 were British-built
computers: the Sinclair
ZX Spectrum , the
BBC Micro and the Amstrad
CPC 464 . In the UK, the 48K Spectrum had not only been released a few
months ahead of the C64's early 1983 debut, but it was also selling
for £175, less than half the C64's £399 price. The Spectrum quickly
became the market leader and Commodore had an uphill struggle against
it. The C64 did however go on to rival the Spectrum in popularity in
the latter half of the 1980s. Adjusted to the size of population, the
Commodore 64 was the highest in Finland where it was
subsequently marketed as "the computer of the republic".
Although rumors spread in late 1983 that Commodore would discontinue
the C64, By early 1985 the C64's price was $149; with an estimated
production cost of $35–50, its profitability was still within the
industry-standard markup of two to three times. Commodore sold about
one million C64s in 1985 and a total of 3.5 million by mid-1986.
Although the company reportedly attempted to discontinue the C64 more
than once in favor of more expensive computers such as the Commodore
128, demand remained strong. In 1986, Commodore introduced the 64C,
a redesigned 64, which _Compute!_ saw as evidence that—contrary to
C64 owners' fears that the company would abandon them in favor of the
Amiga and 128—"the 64 refuses to die". Its introduction also meant
that Commodore raised the price of the C64 for the first time, which
the magazine cited as the end of the home-computer price war .
Software sales also remained strong;
MicroProse , for example, in 1987
cited the Commodore and IBM PC markets as its top priorities.
By 1988, Commodore was still selling between one and one and a half
million C64s worldwide every year, although
Epyx CEO David Shannon
Morse cautioned that "there are no new 64 buyers, or very few. It's a
consistent group that's not growing … it's going to shrink as part
of our business" and most sales volume by the late 1980s was in PAL
regions, the vast majority of US C64 sales having been between
1983-86. One computer-gaming executive stated that the Nintendo
Entertainment System 's enormous popularity—seven million sold that
year, almost as many as the number of C64s sold in its first five
years—had stopped the C64's growth, and
Trip Hawkins stated that
Nintendo was "the last hurrah of the
8-bit world". After 1988 SSI was
the last major American publisher of games for the computer; many new
games, specially arcade conversions, were simply imports from Europe
converted to NTSC. _
Ultima VI _, released in 1991, was the last major
C64 game release from a North American developer.
In the United States, demand for 8 and
16-bit computers all but
ceased as the 1990s began and
32-bit PC compatibles became completely
dominant, but the C64 continued to be popular in the UK and other
European countries. In the end It was not lack of demand or the cost
of the C64 itself (still profitable at a retail price point between
£44 and £50), but the cost of producing the disk drive that ended
the machine's long run. In March 1994, at
Commodore announced that the C64 would be finally discontinued in
1995, noting that the
Commodore 1541 cost more than the C64 itself.
However, only one month later, in April 1994, the company filed for
bankruptcy. It has been widely claimed that between 18 and 22 million
C64s were sold worldwide, however company sales records indicate that
the total number was about 12.5 million. While only 360,000 C64s were
sold in 1982, about 1.3 million were sold in 1983, followed by a major
spike in 1984 when 2.6 million were sold. After that, sales held
steady at between 1.3 and 1.6 million a year for the remainder of the
decade and then dropped off after 1989.
Commodore MAX Machine
In 1982, Commodore released the
Commodore MAX Machine in
Japan . It
was called the Ultimax in the United States, and VC-10 in Germany. The
MAX was intended to be a game console with limited computing
capability, and was based on a very cut-down version of the hardware
family later used in the C64. The MAX was discontinued months after
its introduction because of poor sales in Japan. 1983 saw Commodore
attempt to compete with the
Apple II 's hold on the US education
market with the Educator 64 , essentially a C64 and "greenscale"
monochrome monitor in a PET case. Schools preferred the all-in-one
metal construction of the PET over the standard C64's separate
components, which could be easily damaged, vandalized or stolen.
Schools did not prefer the Educator 64 to the wide range of software
and hardware options the
Apple IIe was able to offer, and it was
produced in limited quantities.
Also in 1983, Commodore released the SX-64 , a portable version of
the C64. The SX-64 has the distinction of being the first _full-color_
portable computer . While earlier computers using this form factor
only incorporate monochrome ("green screen") displays, the base SX-64
unit features a 5 in (130 mm) color cathode ray tube (CRT) and an
integrated 1541 floppy disk drive. Unlike most other C64s, the SX-64
does not have a cassette connector.
Two designers at Commodore, Fred Bowen and
Bil Herd , were determined
to rectify the problems of the Plus/4 . They intended that the
eventual successors to the C64—the
Commodore 128 and 128D computers
(1985)—were to build upon the C64, avoiding the Plus/4's flaws.
The successors had many improvements such as a structured
graphics and sound commands, 80-column display ability, and full CP/M
compatibility. The decision to make the
Commodore 128 plug compatible
with the C64 was made quietly by Bowen and Herd, software and hardware
designers respectively, without the knowledge or approval by the
management in the post
Jack Tramiel era. The designers were careful
not to reveal their decision until the project was too far along to be
challenged or changed and still make the impending Consumer
Electronics Show (CES) in Las Vegas. Upon learning that the C128 was
designed to be compatible with the C64, Commodore's marketing
department independently announced that the C128 would be 100%
compatible with the C64, thereby raising the bar for C64 support. In a
case of malicious compliance , the 128 design was altered to include a
separate "64 mode" using a complete C64 environment to ensure total
Commodore 64C with 1541-II floppy disk drive and 1084S monitor
The C64's designers intended the computer to have a new, wedge-shaped
case within a year of release, but the change did not occur. In 1987,
Commodore released the 64C computer, which is functionally identical
to the original. The exterior design was remodeled in the sleeker
style of the
Commodore 128 . The 64C uses new versions of the SID ,
VIC and I/O chips being deployed, with the core voltage reduced from
12V to 9V. Models with the C64E board had the graphic symbols printed
on the top of the keys, instead of the normal location at the side.
The sound chip (SID) were changed to use the MOS 8580 chip that uses
other filter units, that results in "samples" almost being inaudible.
The 64 KB RAM memory went from eight chips to two chips. Basic and
KERNAL went from two separate chips into one 16 KB ROM chip. The PLA
chip and some TTL chips were integrated into a DIL 64-pin chip. The
"252535-01" PLA integrated the color RAM as well into the same chip.
The smaller physical space made it impossible to put in some internal
expansions like a floppy-speeder. In the United States, the 64C was
often bundled with the third-party GEOS graphical user interface (GUI)
based operating system, as well as the software needed to access
Quantum Link . The 1541 drive received a matching face-lift resulting
in the 1541C. Later a smaller, sleeker 1541-II model was introduced
along with the 800 KB 3.5-inch microfloppy 1581 .
Commodore 64 Games System
Commodore 64 Games System "C64GS"
In 1990, the C64 was repackaged in the form of a game console, called
the C64 Games System (C64GS), with most external connectivity removed.
A simple modification to the 64C's motherboard was made to allow
cartridges to be inserted from above. A modified ROM replaced the
BASIC interpreter with a boot screen to inform the user to insert a
cartridge. Designed to compete with the Nintendo Entertainment System
and the Sega Master System, it suffered from very low sales compared
to its rivals. It was another commercial failure for Commodore, and it
was never released outside Europe.
In 1990, an advanced successor to the C64, the
Commodore 65 (also
known as the "C64DX"), was prototyped, but the project was canceled by
Irving Gould in 1991. The C65's specifications
were impressive for an
8-bit computer, bringing specs comparable to
Apple IIgs . For example, it could display 256 colors on
the screen, while OCS based Amigas could only display 64 in HalfBrite
mode (32 colors and half-bright transformations). Although no specific
reason was given for the C65's cancellation, it would have competed in
the marketplace with Commodore's lower end Amigas and the Commodore
Clones are computers that imitate C64 functions. In the middle of
2004, after an absence from the marketplace of more than 10 years, PC
Tulip Computers BV (owners of the Commodore brand since
1997) announced the
C64 Direct-to-TV (C64DTV), a joystick -based TV
game based on the C64 with 30 video games built into ROM. Designed by
Jeri Ellsworth , a self-taught computer designer who had earlier
designed the modern
C-One C64 implementation, the C64DTV was similar
in concept to other mini-consoles based on the
Atari 2600 and
Intellivision which had gained modest success earlier in the decade.
The product was advertised on
QVC in the United States for the 2004
holiday season. By _"hacking"_ the circuit board , it is possible to
attach C1541 floppy disk drives, hard drives, second joysticks, and
PS/2 -keyboards to these units, which gives the DTV devices nearly all
the capabilities of a full Commodore 64. The DTV hardware is also used
in the mini-console _Hummer_, sold at
RadioShack in mid-2005. In 2015,
Commodore 64 compatible motherboard was produced by Individual
Computers . Dubbed the "C64 Reloaded", it is a modern redesign of the
Commodore 64 motherboard revision 250466 with a few new features. The
motherboard itself is designed to be placed in an empty C64 or C64C
case already owned by the user. Produced in limited quantities, models
Commodore 64 "clone" sports either machined or ZIF sockets in
which the custom C64 chips would be placed. The board also contains
jumpers to accept different revisions of the VIC-II and SID chips, as
well as the ability to jumper between the analogue video system modes
NTSC . The motherboard contains several innovations, including
selection via the RESTORE key of multiple
KERNAL and character ROMs,
built-in reset toggle on the power switch, and an
S-video socket to
replace the original TV modulator . The motherboard is powered by
DC-to-DC converter that uses a single power input of 12 V DC from a
mains adapter to power the unit rather than the original and failure
Commodore 64 power supply brick.
NEWER COMPATIBLE HARDWARE
As of 2008, C64 enthusiasts still develop new hardware, including
Ethernet cards, specially adapted hard disks and flash card
interfaces (sd2iec ).
The C64 "Web.it" Internet Computer
In 1998, the C64 brand was reused for the "Web.it Internet Computer",
a low-powered (even for the time) Internet-oriented , all-in-one x86
PC running Windows 3.1 . Despite its "Commodore 64" nameplate, the
"C64 Web.it" is not directly compatible with the original (except via
included emulation software ), nor does it share its appearance. PC
clones branded as C64x sold by
Commodore USA , LLC, a company
licensing the Commodore trademark , began shipping in June 2011.
The C64x has a case resembling the original C64 computer, but- as with
the "Web.it"- it is based on x86 architecture and is not compatible
Commodore 64 on either hardware or software levels.
Commodore 64 games were released on the Nintendo
Virtual Console service in
Europe and North America only. The games
were unlisted from the service as of August 2013 for unknown reasons.
Commodore 64 software
In 1982, the C64's graphics and sound capabilities were rivaled only
8-bit family , and appeared exceptional when compared
with the widely publicized
Atari VCS and
Apple II . The C64 is often
credited with starting the computer subculture known as the demoscene
Commodore 64 demos ). It is still being actively used in the
demoscene, especially for music (its sound chip even being used in
special sound cards for PCs, and the
Elektron SidStation synthesizer).
Even though other computers quickly caught up with it, the C64
remained a strong competitor to the later video game consoles Nintendo
Entertainment System (NES) and
Sega Master System , thanks in part to
its by-then established software base, especially outside North
America, where it comprehensively outsold the NES.
Due to the unusually high cost of disk drives in the UK, almost all
British C64 software used cassette tapes. Few cassette C64 programs
were released in the US and none after 1983, and in non-UK markets,
the 1541 disk was the universal method of software distribution. The
cartridge slot on the C64 was also mainly a feature used in the
computer's first two years on the market and became rapidly obsolete
once the price and reliability of 1541 drives improved. A handful of
PAL region games used bank switched cartridges to get around the 16k
memory limit. C64 cartridges normally map into $8000 and depending on
the ROM size may extend up to $BFFF, in which case they displace the
BASIC ROM. A special ID string is checked for on power-up; if found,
the kernel will jump to the starting address specified in the ID
string. A few early C64 cartridges released in 1982, used the
so-called MAX Mode, a leftover feature of the failed MAX Machine.
These cartridges map into $F000 rather than $8000 and displace the
kernel ROM. If MAX Mode is used, the programmer will have to provide
his own code for handling system interrupts. Disk and tape software
normally load at the start of
BASIC memory ($801) and use a small
BASIC stub (e.g. 10 SYS(2064)) to jump to the start of the program.
Although no Commodore
8-bit machine except the C128 can automatically
boot from a floppy disk, some software intentionally overwrites
BASIC vectors in the process of loading so that execution
begins automatically rather than requiring the user to type RUN at the
BASIC prompt following loading.
Utility software such as machine language monitors designed to be
used from within
BASIC loads at $8000 or $C000 and can generally be
exited from and control returned to BASIC.
Software that loads at $801
monopolizes the entire system and cannot be exited from aside from
powering the computer off. Commodore did not include a reset button on
any of their computers until the CBM-II line, but there were
third-party cartridges with a reset button on them. It is possible to
trigger a soft reset by jumping to the CPU reset vector at $FCE2. A
few programs use this as an "exit" feature, although it does not clear
Commodore BASIC The Simons'
screen. Note the altered background and text colors (vs the ordinary
C64 blue tones), and the 8 KB reduction of available
memory due to the address space used by the cartridge.
As is common for home computers of the early 1980s, the C64
incorporates a ROM-based version of the
BASIC programming language.
BASIC essentially serves as the operating system for the machine. The
disk drive has its own microprocessor , much like the earlier CBM/PET
systems and the
Atari 400 and
Atari 800 . This means that no memory
space is dedicated to running a disk operating system , as was the
case with earlier systems such as the
Apple II and
Commodore BASIC 2.0 is used instead of the more advanced
from the PET series since C64 users were not expected to need the
disk-oriented enhancements of
BASIC 4.0. The company did not expect
many to buy a disk drive, and using
BASIC 2.0 simplified VIC-20
owners' transition to the 64. "The choice of
BASIC 2.0 instead of 4.0
was made with some soul-searching, not just at random. The typical
user of a C64 is not expected to need the direct disk commands as much
as other extensions and the amount of memory to be committed to BASIC
were to be limited. We chose to leave expansion space for color and
sound extensions instead of the disk features. As a result, you will
have to handle the disk in the more cumbersome manner of the 'old
The version of
BASIC is limited and does not include specific
commands for sound or graphics manipulation, instead requiring users
to use the "
PEEK and POKE " commands to access the graphics and sound
chip registers directly. To provide extended commands, including
graphics and sound, Commodore produced two different cartridge-based
BASIC 2.0: Simons\'
Super Expander 64 . Other
languages available for the C64 include Pascal , C , Logo , Forth ,
FORTRAN . Compilers for
BASIC 2.0 such as Petspeed 2 (from
Commodore), Blitz (from Jason Ranheim) and Turbo Lightning (from Ocean
Software) were produced. Most commercial C64 software was written in
assembly language, either cross developed on a larger computer, or
directly on the C64 using a machine code monitor or an assembler. This
maximized speed and minimized memory use. Some games, particularly
adventures, used high level scripting languages.
ALTERNATIVE OPERATING SYSTEMS
Many third party operating systems have been developed for the C64.
As well as the original GEOS , two third-party GEOS-compatible systems
have been written: Wheels and GEOS megapatch. Both of these require
hardware upgrades to the original C64. Several other operating systems
are or have been available, including WiNGS OS , the Unix-like
operated from a command-line, and the embedded systems OS
with full GUI. Other less well known OSes include ACE, Asterix, DOS/65
GeckOS . A version of
CP/M was released, but this requires the
addition of an external Z80 processor to the expansion bus.
Furthermore, the Z80 processor is underclocked to be compatible with
the C64's memory bus, so performance is poor compared to other CP/M
CP/M and C128
CP/M both suffer a lack of
software; although most commercial
CP/M software can run on these
systems, software media is incompatible between platforms. The low
CP/M on Commodores means that software houses saw no need to
invest in mastering versions for the Commodore disk format. The C64
CP/M cartridge is also not compatible with anything except the early
During the 1980s, the
Commodore 64 was used to run bulletin board
systems using software packages such as Bizarre 64, Blue Board ,
Color 64 , CMBBS, C-Base, DMBBS, Image BBS, EBBS, and The
Deadlock Deluxe BBS Construction Kit, often with sysop -made
modifications. These boards sometimes were used to distribute cracked
software . As late as December 2013, there were 25 such Bulletin Board
Systems in operation, reachable via the
Telnet protocol. There were
major commercial online services , such as
Compunet (UK), CompuServe
(US – later bought by
America Online ), The Source (US) and Minitel
(France) among many others. These services usually required custom
software which was often bundled with a modem and included free online
time as they were billed by the minute.
Quantum Link (or Q-Link) was a
US and Canadian online service for
Commodore 64 and 128 personal
computers that operated from November 5, 1985, to November 1, 1994. It
was operated by
Quantum Computer Services of Vienna , Virginia, which
in October 1991 changed its name to
America Online , and continued to
AOL service for the
IBM PC compatible and Apple Macintosh
Q-Link was a modified version of the
PlayNET system, which Control
Video Corporation (CVC, later renamed Quantum Computer Services)
History of massively multiplayer online games
The first graphical character-based interactive environment is _Club
Caribe _. First released as _Habitat _ in 1988, _Club Caribe_ was
Q-Link customers on their Commodore 64
computers. Users could interact with one another, chat and exchange
items. Although the game's open world was very basic, its use of
online avatars (already well-established off-line by _Ultima_ and
other games) and the combination of chat and graphics was
revolutionary. Online graphics in the late 1980s were severely
restricted by the need to support modem data transfer rates as low as
300 bits per second . Habitat's graphics were stored locally on floppy
disk, eliminating the need for network transfer.
This article MAY CONTAIN TOO MUCH REPETITION OR REDUNDANT LANGUAGE.
Please help improve it by merging similar text or removing repeated
statements. (April 2010)_
CPU AND MEMORY
MOS Technology 6510
The C64 uses an
MOS Technology 6510 microprocessor . This is a
close derivative of the 6502 with an added 6-bit internal I/O port
that in the C64 is used for two purposes: to bank-switch the machine's
read-only memory (ROM) in and out of the processor's address space,
and to operate the datasette tape recorder. The C64 has 64½ KB of RAM
, of which 1024× ½ bytes are color RAM for text mode and 38 KB are
available to built-in
Commodore BASIC 2.0 on startup. There is 20 KB
of ROM, made up of the
BASIC interpreter, the kernel, and the
character ROM. As the processor could only address 64 KB at a time,
the ROM was mapped into memory and only 38,911 bytes of RAM (plus 4 KB
between ROMs) were available at startup. Most "breadbox " Commodore
64s used 4164 DRAM, with eight chips to total up 64k of system RAM.
Late breadbox models and all C64Cs used 41464
DRAM (64kx4) chips which
stored 32 KB per chip, so only two were required. Since 4164 DRAMs are
64kx1, eight chips are needed to make an entire byte and the computer
will not function without all of them present. Thus the first chip
contains Bit 0 for the entire memory space, the second chip contains
Bit 1, and so forth. This also makes detecting faulty RAM easy as a
bad chip will display random characters on the screen and the
character displayed can be used to determine the faulty RAM.
The C64 performs a RAM test on power up and if a RAM error is
detected, the amount of free
BASIC memory will be lower than the
normal 38911 figure. If the faulty chip is in lower memory, then an
?OUT OF MEMORY IN 0 error is displayed rather than the usual BASIC
startup banner. The color RAM at $D800 uses a separate 2114 SRAM chip
and is directly gated to the VIC-II. Unlike the rest of system RAM, it
cannot be banked out by using the $0/$1 register. If a program does
not use the
BASIC interpreter, RAM can be read as well as written over
that ROM's location. However, this means the character ROM is not
available, and the RAM in its place is instead used for the character
glyphs. Normally, this RAM is uninitialized, which then results in
nothing but random patterns appearing on the screen. This is solved by
copying the character ROM into RAM. Most C64 games are written in this
way, using tile maps, which require much processor time and memory.
The same technique was used earlier in the
8-bit family (1979)
and arcade hardware such as _
Pac-Man _ (1981).
The C64 uses a somewhat complicated memory banking scheme; the normal
power-on default is to have the
BASIC ROM mapped in at $A000 and the
screen editor/kernal ROM at $E000. Memory underneath the system ROMs
can be written to, but not read back without swapping out the ROMs. $1
contains a register with control bits for enabling/disabling the
system ROMS as well as the I/O area at $D000. Most software swaps out
BASIC ROM, less often the kernal as the user must then provide his
own code for I/O and interrupt handling. The $D000 page contains the
I/O registers at power on, it can either be swapped with the character
ROM (normally invisible to the CPU) or else simply the bare RAM
underneath. If the I/O registers are swapped out, it is also necessary
to disable interrupts via a SEI instruction. Theoretically, if all
ROMs and the I/O area are swapped out, the entire 64k of system RAM is
accessible to software aside from $0/$1 and the color RAM at $D800. If
the kernel ROM is swapped out,
BASIC will be removed with it and it is
not possible to have
BASIC active without the kernel.
The kernal ROM went through three separate revisions, mostly designed
to fix bugs. The initial version is only found on 326298 motherboards,
used in the first production models, and cannot detect if an
PAL VIC-II is present. The second revision is found on all C64s made
from late 1982 through 1985. The third and last kernel ROM revision
was introduced on the 250466 motherboard (late breadbin models with
41464 RAM) and is found in all C64Cs. The 6510 CPU is clocked at 1.023
MHz (NTSC) and 0.985 MHz (PAL); lower than some competing systems
(for example, the
Atari 800 is clocked at 1.79 MHz). A performance
boost can be gained by disabling the VIC-II's video output via a
register write; this feature is often used by tape and disk
fastloaders as well as the kernel cassette routines.
JOYSTICKS, MICE, AND PADDLES
The C64 retained the DE-9 joystick
Atari joystick port from the
VIC-20 and added another; any
Atari specification game controller can
be used on a C64. The joysticks are read from the registers at $DC00
and $DC01, and most software is designed to use a joystick in port 2
for control rather than port 1, as the upper bits of $DC00 are used by
the keyboard and an I/O conflict can result. Although it is possible
to use Sega gamepads on a C64, it is not recommended as the slightly
different signal generated by them can damage the CIA chip. The Start
button on Sega Genesis controllers outputs a −5V signal; and the
other buttons also pull the lines on the CIA low, which is different
from the behavior of
Atari spec controllers. Register $D419 is used to
control paddles and is an analog input.
Atari paddles are electrically
compatible with the C64, but have different resistance values than
Commodore's paddles, which means most software will not work properly
with them. However, only a handful of games, mostly ones released
early in the computer's life cycle, can use paddles. In 1986,
Commodore released two mice for the C64 and C128, the 1350 and 1351 .
The 1350 is a digital device, read from the joystick registers (and
can be used with any program supporting joystick input); while the
1351 is a true mouse, read with the SID's analog-to-digital converter.
MOS Technology VIC-II
The graphics chip , VIC-II , features 16 colors, eight hardware
sprites per scanline (enabling up to 112 sprites per
scrolling capabilities, and two bitmap graphics modes. The standard
text mode features 40 columns, like most
Commodore PET models; the
built in character encoding is not standard
PETSCII , an
extended form of ASCII-1963. The kernel ROM sets the VIC-II to a dark
blue background on power up with a light blue text and border. Unlike
the PET and VIC-20, the C64 uses "fat" double-width text as some early
VIC-IIs had poor video quality that resulted in a fuzzy picture. Most
screenshots show borders around the screen, which is a feature of the
VIC-II chip. By utilizing interrupts to reset various hardware
registers on precise timings it was possible to place graphics within
the borders and thus use the full screen.
There are two low-resolution and two bitmapped modes. The multicolor
bitmapped mode has an addressable screen of 160 × 200 pixels, with a
maximum of four colors per 4 × 8 character block. The high-resolution
bitmapped mode has an addressable screen of 320 × 200 pixels, with a
maximum of two colors per 8 × 8 character block. Multicolor
low-resolution has a screen of 160 × 200 pixels, 40 × 25 addressable
with four colors per 8 × 8 character block; high resolution "low
resolution" has a screen of 320 × 200 pixels, 40 × 25 addressable
with two colors per 8 × 8 character block. Most C64 video games are
multicolor low-resolution; this allows only block-by-block character
animation due to the limited addressable space.
MOS Technology SID
The SID chip has three channels, each with its own ADSR envelope
generator and filter capabilities.
Ring modulation makes use of
channel N°3, to work with the other two channels. Bob Yannes
developed the SID chip and later co-founded synthesizer company
Ensoniq . Yannes criticized other contemporary computer sound chips as
"primitive, obviously...designed by people who knew nothing about
music". Often the game music has become a hit of its own among C64
users. Well-known composers and programmers of game music on the C64
Rob Hubbard ,
Jeroen Tel , David Whittaker ,
Chris Hülsbeck , Ben
Martin Galway , Kjell Nordbø and David Dunn among many
others. Due to the chip's three channels, chords are often played as
arpeggios , coining the C64's characteristic lively sound. It was also
possible to continuously update the master volume with sampled data to
enable the playback of 4-bit digitized audio. As of 2008, it became
possible to play four channel
8-bit audio samples, 2 SID channels and
still use filtering.
There are two versions of the SID chip: the 6581 and the 8580. The
MOS Technology 6581 was used in the original ("breadbox") C64s, the
early versions of the 64C, and the
Commodore 128 . The 6581 was
replaced with the
MOS Technology 8580 in 1987. While the 6581 sound
quality is a little crisper and many
Commodore 64 fans say they prefer
its sound, it lacks some versatility available in the 8580 – for
example, the 8580 can mix all available waveforms on each channel,
whereas the 6581 can only play a single waveform per channel. The main
difference between the 6581 and the 8580 is the supply voltage. The
6581 uses a 12 volt supply—the 8580, a 9 volt supply. A modification
can be made to use the 6581 in a newer 64C board (which uses the 9
volt chip). The SID chip's distinctive sound has allowed it to retain
a following long after its host computer was discontinued. A number of
audio enthusiasts and companies have designed SID-based products as
add-ons for the C64, x86 PCs, and standalone or Musical Instrument
Digital Interface (MIDI) music devices such as the Elektron SidStation
. These devices use chips taken from excess stock, or removed from
used computers. In 2007,
Timbaland 's extensive use of the SidStation
led to the plagiarism controversy for "Block Party" and "Do It "
Nelly Furtado ).
Commodore made many changes to the C64's hardware during its
lifetime, sometimes causing compatibility issues. The computer's
rapid development, and Commodore and Tramiel's focus on cost cutting
instead of product testing, resulted in several defects that caused
Epyx to complain and required many revisions to fix;
Charpentier said that "not coming a little close to quality" was one
of the company's mistakes.
Cost reduction was the reason for many revisions. Reducing
manufacturing costs was vitally important to Commodore's survival
during the price war and leaner years of the
16-bit era. The C64's
original (NMOS based) motherboard would go through two major
redesigns, (and numerous sub-revisions) exchanging positions of the
VIC-II, SID and PLA chips. Initially, a large portion of the cost was
eliminated by reducing the number of discrete components, such as
diodes and resistors , which enabled the use of a smaller printed
circuit board . There were 16 total C64 motherboard revisions, most of
them aimed at simplifying and reducing manufacturing costs. Some board
revisions were exclusive to
PAL regions. All C64 motherboards were
Hong Kong .
IC locations changed frequently on each motherboard revision, as did
the presence or lack thereof of the metal RF shield around the VIC-II.
PAL boards often had aluminized cardboard instead of a metal shield.
The SID and VIC-II are socketed on all boards, however the other ICs
may be either socketed or soldered. The first production C64s, made in
1982 to early 1983, are known as "silver label" models due to the case
sporting a silver-colored "Commodore" logo. The power LED had a
separate silver badge around it reading "64". These machines also have
only a 5-pin video cable and cannot output S-video. In late 1982,
Commodore introduced the familiar "rainbow badge" case, but many
machines produced into early 1983 also used silver label cases until
the existing stock of them was used up. In the spring of 1983, the
original 326298 board was replaced by the 250407 motherboard which
sported an 8-pin video connector and added
S-video support for the
first time. This case design would be used until the C64C appeared in
1987. All ICs switched to using plastic shells while the silver label
C64s had some ceramic ICs, notably the VIC-II. The case is made from
ABS plastic which may become brown with time. This can be reversed by
using the public domain chemical mix "
Retr0bright ". An early C64
motherboard (Rev A
PAL 1982). A C64C motherboard ("C64E" Rev B
The VIC-II was manufactured with 5 micrometer NMOS technology and
was clocked at either 17.73447 MHz (PAL) or 14.31818 MHz (NTSC).
Internally, the clock was divided down to generate the dot clock
(about 8 MHz) and the two-phase system clocks (about 1 MHz; the exact
pixel and system clock speeds are slightly different between
PAL machines). At such high clock rates, the chip generated a lot of
MOS Technology to use a ceramic dual in-line package
called a "CERDIP". The ceramic package was more expensive, but it
dissipated heat more effectively than plastic.
After a redesign in 1983, the VIC-II was encased in a plastic dual
in-line package, which reduced costs substantially, but it did not
totally eliminate the heat problem. Without a ceramic package, the
VIC-II required the use of a heat sink . To avoid extra cost, the
metal RF shielding doubled as the heat sink for the VIC, although not
all units shipped with this type of shielding. Most C64s in Europe
shipped with a cardboard RF shield , coated with a layer of metal
foil. The effectiveness of the cardboard was highly questionable, and
worse still it acted as an insulator, blocking airflow which trapped
heat generated by the SID, VIC, and PLA chips. The SID was originally
manufactured using NMOS at 7 and in some areas 6 micrometers. The
prototype SID and some very early production models featured a ceramic
dual in-line package, but unlike the VIC-II, these are extremely rare
as the SID was encased in plastic when production started in early
In 1986, Commodore released the last revision to the classic C64
motherboard . It was otherwise identical to the 1984 design, except
for the two 64 kilobit × 4 bit
DRAM chips that replaced the original
eight 64 kilobit × 1 bit ICs. After the release of the Commodore 64C,
MOS Technology began to reconfigure the original C64's chipset to use
HMOS production technology. The main benefit of using
HMOS was that it
required less voltage to drive the IC, which consequently generates
less heat. This enhanced the overall reliability of the SID and
VIC-II. The new chipset was renumbered to 85xx to reflect the change
to HMOS. In 1987, Commodore released a 64C variant with a highly
redesigned motherboard commonly known as a "short board". The new
board used the new
HMOS chipset, featuring a new 64-pin PLA chip. The
new "SuperPLA", as it was dubbed, integrated many discrete components
and transistor–transistor logic (TTL) chips. In the last revision of
the 64C motherboard, the 2114 color RAM was integrated into the
Joystick ports, power switch, power inlet
The C64 used an external power supply , a conventional transformer
with multiple tappings (as opposed to switch mode , the type now used
on PC power supplies), encased in an epoxy resin gel which discouraged
tampering but tended to increase the heat level during use. The design
saved space within the computer's case and allowed international
versions to be more easily manufactured. The 1541-II and 1581 disk
drives, along with various third-party clones, also come with their
own external power supply "bricks", as did most peripherals leading to
a "spaghetti" of cables and the use of numerous double adapters by
Commodore power supplies often failed before expected ; the computer
reportedly had a 30% return rate in late 1983, compared to the 5-7%
the industry considered acceptable. Malfunctioning power bricks were
particularly notorious for damaging the RAM chips as they were made
with the CMOS process rather than NMOS like the main ICs in the
computer and due to their higher density had less tolerance for an
The original PSU included on early 1982-83 machines had a 5-pin
connector and could accidentally be plugged into the video output. To
prevent the user from making this fatal mistake, Commodore changed the
plug design on 250407 motherboards to a 3-pin connector. Commodore
later changed the design, omitting the gel. The follow-on model, the
Commodore 128, used a larger, improved power supply that included a
fuse. The power supply that came with the
Commodore REU was similar to
that of the Commodore 128's unit, providing an upgrade for customers
who purchased that accessory.
MOS Technology 6510 /8500 (the 6510/8500 is a modified 6502 with
an integrated 6-bit I/O port)
* Clock speed: 0.985 MHz (
PAL ) or 1.023 MHz (
MOS Technology VIC-II 6567/8562 (NTSC), 6569/8565 (PAL)
* 16 colors
* Text mode: 40×25 characters; 256 user-defined chars (8×8 pixels
, or 4×8 in multicolor mode); or extended background color; 64
user-defined chars with 4 background colors, 4-bit color RAM defines
* Bitmap modes: 320×200 (2 unique colors in each 8×8 pixel block),
160×200 (3 unique colors + 1 common color in each 4×8 block)
* 8 hardware sprites of 24×21 pixels (12×21 in multicolor mode)
* Smooth scrolling, raster interrupts
MOS Technology 6581/8580 SID
* 3-channel synthesizer with programmable
* 8 octaves
* 4 waveforms per audio channel: triangle , sawtooth , variable
pulse , noise
* Oscillator synchronization , ring modulation
* Programmable filter: high pass , low pass , band pass , notch
* Input/Output: Two 6526 Complex Interface Adapters
* 16 bit parallel I/O
* 8 bit serial I/O
* 24-hours (AM/PM) Time of Day clock (TOD), with programmable alarm
* 16 bit interval timers
* 64 KB, of which 38 KB (minus 1 byte) were available for BASIC
* 512 bytes color RAM (memory allocated for screen color data
* Expandable to 320 KB with Commodore 1764 256 KB RAM Expansion Unit
(REU); although only 64 KB directly accessible; REU mostly intended
for GEOS . REUs of 128 KB and 512 KB, originally designed for the
C128, were also available, but required the user to buy a stronger
power supply from some third party supplier; with the 1764 this was
Creative Micro Designs also produced a 2 MB REU for the C64
and C128, called the 1750 XL. The technology actually supported up to
16 MB, but 2 MB was the biggest one officially made. Expansions of up
to 16 MB were also possible via the CMD
* 20 KB (9 KB
Commodore BASIC 2.0; 7 KB
KERNAL ; 4 KB character
generator, providing two 2 KB character sets)
Input/output (I/O) Ports And Power Supply
Commodore 64 ports (from left: Joy1, Joy2, Power, ROM cartridge
, RF-adj, RF , A/V, 488 , Tape, User)
* I/O ports:
ROM cartridge expansion slot (44-pin slot for edge connector with
6510 CPU address/data bus lines and control signals, as well as GND
and voltage pins; used for program modules and memory expansions,
RF modulator antenna output via a
RCA connector . The
used channel could be adjusted from number 36 with the potentiometer
to the left.
DIN connector containing composite video output, separate
Y/C outputs and sound input/output. Beware that this is the 262°
(horseshoe) version of the plug, not the 270° circular version. Early
C64 units (with motherboard Assy 326298) use a 5-pin DIN connector
that carries composite video and luminance signals, but lacks a chroma
* Serial bus (proprietary serial version of
IEEE-488 , 6-pin DIN
plug) for CBM printers and disk drives
* PET -type
Commodore Datassette 300 baud tape interface (edge
connector with digital cassette motor/read/write/key-sense signals,
Ground and +5V DC lines. The cassette motor is controlled by a +5V DC
signal from the 6502 CPU. The 9V AC input is transformed into
unregulated 6.36V DC which is used to actually power the cassette
* User port (edge connector with TTL -level signals, for modems and
so on.; byte-parallel signals which can be used to drive third-party
parallel printers, among other things, 17 logic signals, 7 Ground and
voltage pins, including 9V AC)
* 2 × screwless DE9M game controller ports (compatible with Atari
2600 controllers ), each supporting five digital inputs and two analog
inputs. Available peripherals included digital joysticks , analog
paddles , a light pen , the
Commodore 1351 mouse , and graphics
tablets such as the
* Power supply:
* 5V DC and 9V AC from an external "power brick", attached to a
7-pin female DIN-connector on the computer.
The 9 volt AC is used to supply power via a charge pump to the SID
sound generator chip, provide 6.8V via a rectifier to the cassette
motor, a "0" pulse for every positive half wave to the time-of-day
(TOD) input on the CIA chips, and 9 volts AC directly to the
user-port. Thus, as a minimum, a 12 V square wave is required. But a 9
V sine wave is preferred.
Note that even if I/O chips like VIC-II only uses 64 positions in the
memory address space, it will occupy 1,024 addresses because some
address bits are left undecoded.
Commodore 64 peripherals
Commodore 1541 Floppy Drive
Commodore 1541C Floppy Drive
Commodore 1541-II Floppy Drive
Commodore 1530 Datasette
Dot matrix printer
Commodore 1351 Mouse
Commodore 1702 video monitor
Vertical integration was the key to keep costs low. At the
introduction in 1982, the production cost was US$135 and the retail
price US$595. In 1985, the retail cost went down to US$149 (equivalent
to $331.79 in 2016) and the production cost were believed to be
somewhere between US$35–50 (c. US$80–110 today). Commodore
would not confirm this cost figure. Dougherty of the Berkeley
Softworks estimated the costs of the
Commodore 64 parts based on his
PRICE IN 1985 US$
SID (sound) chip
VIC-II (graphics) chip
RF modulator package
A handful of TTL , buffers, power regulators and capacitors
Printed circuit board board
Power supply and miscellaneous connectors
Packaging and manual
52.8 – 61.8
To lower costs TTL chips were replaced with less expensive custom
chips and ways to increase the yields on the sound and graphics chips
were found. The video chip 6567 had the ceramic package replaced with
plastic but heat dissipation demanded a redesign of the chip and the
development of a plastic package that can dissipate heat as well as
The computer's designers claimed that "The freedom that allowed us to
do the C-64 project will probably never exist again in that
environment"; by spring 1983 most had left to found
BYTE _ in July 1983 stated that "the 64 retails for $595. At that
price it promises to be one of the hottest contenders in the
under-$1000 personal computer market". It described SID as "a true
music synthesizer...the quality of the sound has to be heard to be
believed", while criticizing the use of
Commodore BASIC 2.0, the
floppy disk performance which is "even slower than the
drive", and Commodore's quality control.
Commodore 64 emulators include the open source
VICE , Hoxs64 and
* Computer Science portal
* 1980s portal
History of personal computers
IDE64 – P-ATA interface cartridge for the C64
List of Commodore 64 games
SuperCPU – CPU upgrade for C64 and C128
* ^ The "C=" represents the graphical part of the logo.
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Commodore 64 turns 30: What do today\'s kids make of it?". BBC
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