The Kenbak-1 is considered by the
Computer History Museum
The Computer History Museum (CHM) is a museum of computer history, located in Mountain View, California. The museum presents stories and artifacts of Silicon Valley and the information age, and explores the computing revolution and its impact on ...
, the
Computer Museum of America
The Computer Museum of America was established in Roswell, Georgia and opened in July 2019 to coincide with the fiftieth anniversary of the Moon landing. It is the largest technology museum on the East Coast with the opening of Phase I and when co ...
and the
American Computer Museum
The American Computer & Robotics Museum (ACRM), formerly known as the American Computer Museum, is a museum of the history of computing, Communication protocol, communications, artificial intelligence and robotics that is located in Bozeman, Mont ...
to be the world's first "
personal computer
A personal computer (PC) is a multi-purpose microcomputer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or tec ...
", invented by John Blankenbaker (born 1929) of Kenbak Corporation in 1970, and first sold in early 1971. Less than 50 machines were ever built using
Bud Industries enclosures as its housing. The system first sold for
US$
The United States dollar (symbol: $; code: USD; also abbreviated US$ or U.S. Dollar, to distinguish it from other dollar-denominated currencies; referred to as the dollar, U.S. dollar, American dollar, or colloquially buck) is the official ...
750. Today, only 14 machines are known to exist worldwide, in the hands of various collectors and museums. Production of the Kenbak-1 stopped in 1973 as Kenbak failed, and was taken over by CTI Education Products, Inc. CTI rebranded the inventory and renamed it the 5050, though sales remained elusive.
Since the Kenbak-1 was invented before the first
microprocessor
A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circu ...
, the machine didn't have a one-chip
CPU but instead was based purely on
small-scale integration
An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny M ...
TTL
TTL may refer to:
Photography
* Through-the-lens metering, a camera feature
* Zenit TTL, an SLR film camera named for its TTL metering capability
Technology
* Time to live, a computer data lifespan-limiting mechanism
* Transistor–transistor lo ...
chip Chromatin immunoprecipitation (ChIP) is a type of immunoprecipitation experimental technique used to investigate the interaction between proteins and DNA in the cell. It aims to determine whether specific proteins are associated with specific genom ...
s.
[ The ]8-bit
In computer architecture, 8-bit Integer (computer science), integers or other Data (computing), data units are those that are 8 bits wide (1 octet (computing), octet). Also, 8-bit central processing unit (CPU) and arithmetic logic unit (ALU) arc ...
machine offered 256 byte
The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable unit ...
s of memory
Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembered, ...
, implemented on Intel
Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California. It is the world's largest semiconductor chip manufacturer by revenue, and is one of the developers of the x86 seri ...
's type 1404A silicon gate
In semiconductor electronics fabrication technology, a self-aligned gate is a transistor manufacturing approach whereby the gate electrode of a MOSFET (metal–oxide–semiconductor field-effect transistor) is used as a mask for the doping of th ...
MOS shift register
A shift register is a type of digital circuit using a cascade of flip-flops where the output of one flip-flop is connected to the input of the next. They share a single clock signal, which causes the data stored in the system to shift from one loc ...
s. The instruction cycle
The instruction cycle (also known as the fetch–decode–execute cycle, or simply the fetch-execute cycle) is the cycle that the central processing unit (CPU) follows from boot-up until the computer has shut down in order to process instruction ...
time was 1 microsecond
A microsecond is a unit of time in the International System of Units (SI) equal to one millionth (0.000001 or 10−6 or ) of a second. Its symbol is μs, sometimes simplified to us when Unicode is not available.
A microsecond is equal to 1000 n ...
(equivalent to an instruction clock speed of 1 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 ...
), but actual execution speed averaged below 1000 instructions per second due to architectural constraints such as slow access to serial memory.machine code
In computer programming, machine code is any low-level programming language, consisting of machine language instructions, which are used to control a computer's central processing unit (CPU). Each instruction causes the CPU to perform a very ...
using an array of buttons and switches. Output consisted of a row of lights.
Internally, the Kenbak-1 has a serial computer
A serial computer is a computer typified by bit-serial architecture i.e., internally operating on one bit or digit for each clock cycle. Machines with serial main storage devices such as acoustic or magnetostrictive delay lines and rotating ma ...
architecture, processing one bit at a time."Official Kenbak-1 Reproduction Kit"
Technical description
Registers
The Kenbak-1 has a total of nine registers. All are memory mapped. It has three general-purpose registers: A, B and X. Register A is the implicit destination of some operations. Register X is also known as the index register and turns the direct and indirect modes into indexed direct and indexed indirect modes. It also has program counter, called Register P, three "overflow and carry" registers for A, B and X respectively as well as an Input Register and an Output Register.
[
]
Instruction table
The instructions are encoded in 8 bits, with a possible second byte providing an immediate value or address. Some instructions have multiple possible encodings.["Programming Reference Manual KENBAK-l Computer"]
/ref>
See also
*Datapoint 2200
The Datapoint 2200 was a mass-produced programmable computer terminal usable as a computer, designed by Computer Terminal Corporation (CTC) founders Phil Ray and Gus Roche and announced by CTC in June 1970 (with units shipping in 1971). It was i ...
, a contemporary machine with alphanumeric screen and keyboard, suitable to run non-trivial application programs
*Mark-8
The Mark-8 is a microcomputer design from 1974, based on the Intel 8008 CPU (which was the world's first 8-bit microprocessor). The Mark-8 was designed by Jonathan Titus, a Virginia Tech graduate student in Chemistry. After building the machine ...
, designed by graduate studen
Jonathan A. Titus
and announced as a 'loose kit' in the July 1974 issue of ''Radio-Electronics
''Radio-Electronics'' was an American electronics magazine that was published under various titles from 1929 to 2003. Hugo Gernsback, sometimes called the father of science fiction, started it as ''Radio-Craft'' in July 1929. The title was changed ...
'' magazine
*Altair 8800
The Altair 8800 is a microcomputer designed in 1974 by MITS and based on the Intel 8080 CPU. Interest grew quickly after it was featured on the cover of the January 1975 issue of Popular Electronics and was sold by mail order through advertiseme ...
, a very popular 1975 microcomputer that provided the inspiration for starting Microsoft
Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washing ...
References
{{Reflist, refs=
[{{cite web
, url = https://archive.computerhistory.org/resources/access/text/2013/05/102702235-05-01-acc.pdf
, title = Oral History of John Blankenbaker
, publisher = Computer History Museum
, date = June 14, 2007]
External links
Kenbak.com
Comprehensive Kenbak-1 history and technical information
Article
KENBAK-1 Computer
– Official Kenbak-1 website at www.kenbak-1.info
– Official Kenbak-1 reproduction kit at www.kenbakkit.com
– Online Kenbak-1 Emulator
Kenbak-1 Emulator
– Kenbak-1 Emulator download
Kenbak 1
– Images and information at www.vintage-computer.com
Kenbak
documentation at bitsavers.org
Hardware-based Kenbak-1 Emulator
Recreating the First PC
article about KENBAK-uino at hackaday.com
KENBAK-1 Emulator/Trainer
RetroWiki.es (Invalid, 2015-02-10)
The Kenbak-1 Prototype
Official Kenbak-1 prototype website at www.thefirstpc.com
Early microcomputers
Computer-related introductions in 1971
Serial computers
8-bit computers