The

Tangerine The tangerine is a type of citrus fruit that is orange in color. Its scientific name varies. It has been treated as a separate species under the name ''Citrus tangerina'' or ''Citrus'' × ''tangerina'', or treated as a variety of ''Citrus retic ...

Microtan 65 (sometimes abbreviated M65) was a

6502 The MOS Technology 6502 (typically pronounced "sixty-five-oh-two" or "six-five-oh-two") William Mensch and the moderator both pronounce the 6502 microprocessor as ''"sixty-five-oh-two"''. is an 8-bit microprocessor that was designed by a small te ...

based single board

microcomputer A microcomputer is a small, relatively inexpensive computer having a central processing unit (CPU) made out of a microprocessor. The computer also includes memory and input/output (I/O) circuitry together mounted on a printed circuit board (PC ...

, first sold in 1979, which could be expanded into, what was for its day, a comprehensive and powerful system. The design became the basis for what later became the

ORIC Oric was the name used by UK-based Tangerine Computer Systems for a series of 6502-based home computers sold in the 1980s, primarily in Europe. With the success of the ZX Spectrum from Sinclair Research, Tangerine's backers suggested a hom ...

ATMOS and later

computer A computer is a machine that can be programmed to Execution (computing), carry out sequences of arithmetic or logical operations (computation) automatically. Modern digital electronic computers can perform generic sets of operations known as C ...

s, which has similar keyboard addressing and tape I/O as in the Microtan 65. The Microtan 65 has a single step function that can be used for

debugging In computer programming and software development, debugging is the process of finding and resolving '' bugs'' (defects or problems that prevent correct operation) within computer programs, software, or systems. Debugging tactics can involve in ...

at the hardware level. The computer was available as ready-built

board Board or Boards may refer to: Flat surface * Lumber, or other rigid material, milled or sawn flat ** Plank (wood) ** Cutting board ** Sounding board, of a musical instrument * Cardboard (paper product) * Paperboard * Fiberboard ** Hardboard, a ty ...

s or as kits consisting of board and

components Circuit Component may refer to: •Are devices that perform functions when they are connected in a circuit. In engineering, science, and technology Generic systems * System components, an entity with discrete structure, such as an assem ...

requiring

soldering Soldering (; ) is a process in which two or more items are joined by melting and putting a filler metal (solder) into the joint, the filler metal having a lower melting point than the adjoining metal. Unlike welding, soldering does not involv ...

together. The Microtan 65 was intended as a general purpose microcomputer which could be used by

laboratories A laboratory (; ; colloquially lab) is a facility that provides controlled conditions in which scientific or technological research, experiments, and measurement may be performed. Laboratory services are provided in a variety of settings: physicia ...

Original Equipment Manufacturers An original equipment manufacturer (OEM) is generally perceived as a company that produces non-aftermarket parts and equipment that may be marketed by another manufacturer. It is a common industry term recognized and used by many professional or ...

(OEMs) and the computer enthusiast, and it was designed with expandability in mind. In this way the customer could customise the system, be it as a specialised

control system A control system manages, commands, directs, or regulates the behavior of other devices or systems using control loops. It can range from a single home heating controller using a thermostat controlling a domestic boiler to large industrial c ...

, as a learning tool, or as a general purpose computing device. Price of the Microtan 65 board in 1981 was £79.35 (inc.

VAT A value-added tax (VAT), known in some countries as a goods and services tax (GST), is a type of tax that is assessed incrementally. It is levied on the price of a product or service at each stage of production, distribution, or sale to the en ...

) in kit form or £90.85 ready-assembled. The system was not generally available in the shops. To accompany the hardware and to offer further support to users, a magazine was created, the ''Tansoft Gazette'' (name inspired by the ''

Liverpool Software Gazette ''Liverpool Software Gazette'' was a short-lived computer magazine published by Microdigital Ltd, a company who were based in Liverpool, England and run by Bruce Everiss. History The magazine was in print for only eight issues of which the last w ...

''). This was edited by Tangerine employee Paul Kaufman who continued as editor when the magazine was renamed ''Oric Owner''. Tansoft also became the name of Tangerine Computer's official software house which supplied a number of software products and books for the Microtan system and subsequently for the

Oric Oric was the name used by UK-based Tangerine Computer Systems for a series of 6502-based home computers sold in the 1980s, primarily in Europe. With the success of the ZX Spectrum from Sinclair Research, Tangerine's backers suggested a hom ...

range of computers.

Main board

The Microtan 65 was quite simple by today's standards, with: * an NMOS

CPU running at 750

kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...

clock rate In computing, the clock rate or clock speed typically refers to the frequency at which the clock generator of a processor can generate pulses, which are used to synchronize the operations of its components, and is used as an indicator of the pr ...

* 1K byte of

RAM Ram, ram, or RAM may refer to: Animals * A male sheep * Ram cichlid, a freshwater tropical fish People * Ram (given name) * Ram (surname) * Ram (director) (Ramsubramaniam), an Indian Tamil film director * RAM (musician) (born 1974), Dutch * ...

, used both for display memory and user programs * 1K byte of

ROM Rom, or ROM may refer to: Biomechanics and medicine * Risk of mortality, a medical classification to estimate the likelihood of death for a patient * Rupture of membranes, a term used during pregnancy to describe a rupture of the amniotic sac * ...

for the monitor program * video logic and a

television Television, sometimes shortened to TV, is a telecommunication medium for transmitting moving images and sound. The term can refer to a television set, or the medium of television transmission. Television is a mass medium for advertisin ...

RF modulator An RF modulator (or radio frequency modulator) is an electronic device whose input is a baseband signal which is used to modulate a radio frequency source. RF modulators are used to convert signals from devices such as media players, VCRs a ...

, for the 16 rows of 32 characters display * a

software Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work. At the lowest programming level, executable code consists ...

scanned

hexadecimal In mathematics and computing, the hexadecimal (also base-16 or simply hex) numeral system is a positional numeral system that represents numbers using a radix (base) of 16. Unlike the decimal system representing numbers using 10 symbols, hexa ...

keypad A keypad is a block or pad of buttons set with an arrangement of digits, symbols, or alphabetical letters. Pads mostly containing numbers and used with computers are numeric keypads. Keypads are found on devices which require mainly numeric in ...

* an optional

ASCII ASCII ( ), abbreviated from American Standard Code for Information Interchange, is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment, and other devices. Because of ...

keyboard Keyboard may refer to: Text input * Keyboard, part of a typewriter * Computer keyboard ** Keyboard layout, the software control of computer keyboards and their mapping ** Keyboard technology, computer keyboard hardware and firmware Music * Musi ...

Display

The major advance that the Microtan 65 had over a lot of the competition at that time was that the

video display A display device is an output device for presentation of information in visual or tactile form (the latter used for example in tactile electronic displays for blind people). When the input information that is supplied has an electrical signal the ...

was flicker free. At the time a lot of microcomputers would either access the screen memory asynchronously to the video timing (causing flicker and splats on the screen), or would write to the screen memory during a non-display period (which was slow). The Microtan 65 got over this problem by making use of an incidental feature of the

. The 6502 (unlike most other CPUs) has a regular period in each instruction cycle when all CPU activity is inside the chip, leaving the external memory available without using complex external arbitration logic. This made

design simpler and meant that video accesses could be made at maximum speed. This technique is also used on the

Oric-1 Oric was the name used by UK-based Tangerine Computer Systems for a series of 6502-based home computers sold in the 1980s, primarily in Europe. With the success of the ZX Spectrum from Sinclair Research, Tangerine's backers suggested a hom ...

and Atmos, and in the unrelated

Apple II The Apple II (stylized as ) is an 8-bit home computer and one of the world's first highly successful mass-produced microcomputer products. It was designed primarily by Steve Wozniak; Jerry Manock developed the design of Apple II's foam-m ...

. The 32×16 characters was the reason that the 6502 was clocked at 750 kHz. To get the circuitry to work at a (nearly) standard video rate meant that the

pixel In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device. In most digital display devices, pixels are the smal ...

clock had to be 6

MHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one he ...

. When the Microtan 65 was designed only a 1 MHz 6502 was available, and so 750 kHz was used (6 MHz divided by 8).

Software

The 1K byte

monitor Monitor or monitor may refer to: Places * Monitor, Alberta * Monitor, Indiana, town in the United States * Monitor, Kentucky * Monitor, Oregon, unincorporated community in the United States * Monitor, Washington * Monitor, Logan County, West ...

program (later increased to a 2K) is called TANBUG. The

facilities were rudimentary: * M = Memory modify / examine * L = List a block of memory * G = Go command (Run a program) * R = Registers display / modify * S = set Single step mode * N = set Normal mode (cancel S command) * P = Proceed command (execute next instruction in Single step mode) * B = set

Breakpoint In software development, a breakpoint is an intentional stopping or pausing place in a program, put in place for debugging purposes. It is also sometimes simply referred to as a pause. More generally, a breakpoint is a means of acquiring knowle ...

s * O = calculate Offset for use in branch instructions * C = Copy a block of memory

Memory map

The Microtan 65 memory map is shown below ($ representing a

memory address): *

Zero Page The zero page or base page is the block of memory at the very beginning of a computer's address space; that is, the page whose starting address is zero. The size of a page depends on the context, and the significance of zero page memory versus h ...

Stack Stack may refer to: Places * Stack Island, an island game reserve in Bass Strait, south-eastern Australia, in Tasmania’s Hunter Island Group * Blue Stack Mountains, in Co. Donegal, Ireland People * Stack (surname) (including a list of people ...

* Screen

* * End of Microtan 65 RAM - map continued from to as RAM on TANEX * I/O * * TANBUG V2 * The screen memory occupies the space between and . In addition to the standard 8

bit The bit is the most basic unit of information in computing and digital communications. The name is a portmanteau of binary digit. The bit represents a logical state with one of two possible values. These values are most commonly represente ...

s of screen

, there was an additional single bit RAM shadowing the to space. This was configured as a 9th

write-only plane, and was used by the Microtan 65 for rudimentary, or "chunky", graphics. Setting the 9th bit displayed a

Minitel The Minitel was a videotex online service accessible through telephone lines, and was the world's most successful online service prior to the World Wide Web. It was invented in Cesson-Sévigné, near Rennes in Brittany, France. The service was ...

type block graphic. The display is 32 characters across by 16 lines down, with memory address representing the top left hand displayed character, the second row, etc. The character representation is standard

. Several pieces of Microtan 65 software write to the bottom line by writing to memory starting at - the leftmost character on the bottom line, rather than vectoring through TANBUG.

Input/output

I/O in the Microtan 65 is decoded into a 16 KB space to simplify the hardware. In fact the 1 KB of

is mirrored through the bottom 32 KB, the I/O through the next 16 KB, and the

EPROM An EPROM (rarely EROM), or erasable programmable read-only memory, is a type of programmable read-only memory (PROM) chip that retains its data when its power supply is switched off. Computer memory that can retrieve stored data after a power s ...

through the top 16 KB. If you added an expansion board (see TANEX below) the decoding was modified and the wasted space reclaimed. In common with other

designs, I/O is mapped into the memory space. There is no dedicated I/O space as on the

Z80 The Z80 is an 8-bit microprocessor introduced by Zilog as the startup company's first product. The Z80 was conceived by Federico Faggin in late 1974 and developed by him and his 11 employees starting in early 1975. The first working samples were ...

8086 The 8086 (also called iAPX 86) is a 16-bit microprocessor chip designed by Intel between early 1976 and June 8, 1978, when it was released. The Intel 8088, released July 1, 1979, is a slightly modified chip with an external 8-bit data bus (allowi ...

etc. The I/O ports are (when fully decoded): *Write to Clear

Keyboard Keyboard may refer to: Text input * Keyboard, part of a typewriter * Computer keyboard ** Keyboard layout, the software control of computer keyboards and their mapping ** Keyboard technology, computer keyboard hardware and firmware Music * Musi ...

Flag (Keyboard would generate an IRQ) *Read from Turn Graphics On (enables "9th

" graphics writes) *Write to Used by the hardware single step *Write to To write a scan pattern to the hex

(if fitted) *Write to Turn off Graphics (disable "9th

" graphics writes) *Read From Read Keyboard Port (either keypad or

keyboard)

TANEX expansion board

. Adding a TANEX board provided a number of features: * an add-on to TANBUG called XBUG * space for an additional 7K bytes of

* five

sockets * two 6522 VIAs * a 6551

UART A universal asynchronous receiver-transmitter (UART ) is a computer hardware device for asynchronous serial communication in which the data format and transmission speeds are configurable. It sends data bits one by one, from the least significan ...

, providing a

cassette Cassette may refer to: Technology * Cassette tape (or ''musicassette'', ''audio cassette'', ''cassette tape'', or ''tape''), a worldwide standard for analog audio recording and playback ** Cassette single (or "Cassingle"), a music single in th ...

interface for storing and retrieving programs (300 baud CUTS, and 2400

baud In telecommunication and electronics, baud (; symbol: Bd) is a common unit of measurement of symbol rate, which is one of the components that determine the speed of communication over a data channel. It is the unit for symbol rate or modulatio ...

), and a

serial interface In computing, a serial port is a serial communication interface through which information transfers in or out sequentially one bit at a time. This is in contrast to a parallel port, which communicates multiple bits simultaneously in parallel. T ...

Without a TANEX board, and due to deliberately ambiguous address decoding, the address would appear to the

to have the same data as . In TANBUG, this is a jump to an internal monitor routine. With TANEX installed, is decoded properly, and that address is an entry point into XBUG. XBUG provided features such as

cassette tape The Compact Cassette or Musicassette (MC), also commonly called the tape cassette, cassette tape, audio cassette, or simply tape or cassette, is an analog magnetic tape recording format for audio recording and playback. Invented by Lou Ottens ...

loading and saving, a simple

assembler Assembler may refer to: Arts and media * Nobukazu Takemura, avant-garde electronic musician, stage name Assembler * Assemblers, a fictional race in the ''Star Wars'' universe * Assemblers, an alternative name of the superhero group Champions of A ...

disassembler A disassembler is a computer program that translates machine language into assembly language—the inverse operation to that of an assembler. A disassembler differs from a decompiler, which targets a high-level language rather than an assembly lan ...

, hex calculator. The

sockets on TANEX could be used to run a 10K Microsoft Extended BASIC, a

two-pass assembler In computer programming, assembly language (or assembler language, or symbolic machine code), often referred to simply as Assembly and commonly abbreviated as ASM or asm, is any low-level programming language with a very strong correspondence be ...

, or even (and more likely given the hardware bias of the Microtan 65) code written for a specific hardware control application. Price of the TANEX board in 1981 was as a "minimum configuration" kit - lacking one of the 6522 VIAs and the 6551 and with 1K of RAM - and £60.95 for a similar board fully assembled. TANEX was also available with the board fully populated with chips (although excluding XBUG, ROMs & BASIC) and in this form the costs were for the kit and ready assembled.

Further Expansion

The Microtan 65 was designed as a modular system able to be expanded as required, and for this each board included an 80-pin connector at one end allowing it to be plugged into a backplane-type

motherboard A motherboard (also called mainboard, main circuit board, mb, mboard, backplane board, base board, system board, logic board (only in Apple computers) or mobo) is the main printed circuit board (PCB) in general-purpose computers and other expand ...

. A simple two-socket "Mini Motherboard" connected the Microtan 65 and TANEX boards for minimum expansion and in this form the system was also available ready-built from Tangerine, complete with case and full ASCII keyboard, as the Tangerine Micron, costing £395.00 in 1981. For further expansion the builder could purchase the full "System Motherboard" which featured an additional ten sockets, bringing the total available sockets to twelve. For housing this, a "System Rack", rack-based case was available, in black and silver with a black front panel trimmed in Tangerine's trademark orange. Additional boards became available with time, including a 40K memory board - TANRAM, made up of 32K of

dynamic Dynamics (from Greek δυναμικός ''dynamikos'' "powerful", from δύναμις ''dynamis'' "power") or dynamic may refer to: Physics and engineering * Dynamics (mechanics) ** Aerodynamics, the study of the motion of air ** Analytical dynam ...

and 8K of

static Static may refer to: Places *Static Nunatak, a nunatak in Antarctica United States * Static, Kentucky and Tennessee *Static Peak, a mountain in Wyoming **Static Peak Divide, a mountain pass near the peak Science and technology Physics *Static el ...

, bringing the total non-paged memory to 48K, a dedicated

parallel Parallel is a geometric term of location which may refer to: Computing * Parallel algorithm * Parallel computing * Parallel metaheuristic * Parallel (software), a UNIX utility for running programs in parallel * Parallel Sysplex, a cluster of IBM ...

I/O board featuring 16 parallel input/output

port A port is a maritime facility comprising one or more wharves or loading areas, where ships load and discharge cargo and passengers. Although usually situated on a sea coast or estuary, ports can also be found far inland, such as Ham ...

s; a similar dedicated serial I/O board featuring 8 serial input/output ports, a

disk controller {{unreferenced, date=May 2010 The disk controller is the controller circuit which enables the CPU to communicate with a hard disk, floppy disk or other kind of disk drive. It also provides an interface between the disk drive and the bus conne ...

board for use with

disk drives Data storage is the recording (storing) of information (data) in a storage medium. Handwriting, phonographic recording, magnetic tape, and optical discs are all examples of storage media. Biological molecules such as RNA and DNA are consi ...

, a Disk Operating System - TANDOS 65, a high resolution

graphics Graphics () are visual images or designs on some surface, such as a wall, canvas, screen, paper, or stone, to inform, illustrate, or entertain. In contemporary usage, it includes a pictorial representation of data, as in design and manufacture ...

board featuring 8K of static graphics RAM giving a resolution of 256 × 256

s, a dedicated 32K

board, (aimed mainly at

OEM An original equipment manufacturer (OEM) is generally perceived as a company that produces non-aftermarket parts and equipment that may be marketed by another manufacturer. It is a common industry term recognized and used by many professional or ...

and general purpose applications or for use with AIM,

KIM Kim or KIM may refer to: Names * Kim (given name) * Kim (surname) ** Kim (Korean surname) *** Kim family (disambiguation), several dynasties **** Kim family (North Korea), the rulers of North Korea since Kim Il-sung in 1948 ** Kim, Vietnamese f ...

and SYM systems), capable of holding either 8 × 2732 or 16 × 2716 EPROMs; and a 32K RAM board featuring two 16K banks of 4116 dynamic RAM, again intended for similar purposes to the 32K ROM board. In addition, several

third-party Third party may refer to: Business * Third-party source, a supplier company not owned by the buyer or seller * Third-party beneficiary, a person who could sue on a contract, despite not being an active party * Third-party insurance, such as a Veh ...

suppliers offered boards designed for use with the Microtan 65 system. In addition to the BASIC

programming language A programming language is a system of notation for writing computer programs. Most programming languages are text-based formal languages, but they may also be graphical. They are a kind of computer language. The description of a programming ...

Tangerine also released on disk TANFORTH, an extended version of FIG FORTH featuring a full FORTH

compiler In computing, a compiler is a computer program that translates computer code written in one programming language (the ''source'' language) into another language (the ''target'' language). The name "compiler" is primarily used for programs that ...

and

editor Editing is the process of selecting and preparing written, photographic, visual, audible, or cinematic material used by a person or an entity to convey a message or information. The editing process can involve correction, condensation, orga ...

References

External links

* This article was based on:
Geoff Mcdonald's webpage
- author's experience with the Microtan 65

- includes a Microtan 65

emulator In computing, an emulator is Computer hardware, hardware or software that enables one computer system (called the ''host'') to behave like another computer system (called the ''guest''). An emulator typically enables the host system to run so ...

written in

Java Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's List ...

Binary Dinosaurs
- tracing the history of computers
www.microtan.ukpc.net
- manuals, ROM images, magazine and newsletter articles

- A new look at the Microtan 65 - a DIY micro that narrowly escaped extinction * {{Cite news , title=The Oric-1 is 30 , url=https://www.theregister.co.uk/2013/01/28/the_oric_1_is_30_years_old/ , date=28 Jan 2013 , author=Tony Smith , journal=

The Register ''The Register'' is a British technology news website co-founded in 1994 by Mike Magee, John Lettice and Ross Alderson. The online newspaper's masthead sublogo is "''Biting the hand that feeds IT''." Their primary focus is information tec ...

6502-based home computers Home computers Early microcomputers Computer-related introductions in 1979 Tangerine Computer Systems