The Newbear 77-68 was a kit of parts from which a purchaser could construct a first generation home computer based around a

Motorola 6800 The 6800 ("''sixty-eight hundred''") is an 8-bit computing, 8-bit microprocessor designed and first manufactured by Motorola in 1974. The MC6800 microprocessor was part of the Motorola 6800 family, M6800 Microcomputer System (latter dubbed ''68xx' ...

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 ...

. Because it was designed to be assembled by its owner at home, it was also a

homebuilt computer A custom-built or homebuilt computer is a computer assembled from available components, usually commercial off-the-shelf (COTS) components, rather than purchased as a complete system from a computer system supplier, also known as pre-built system ...

. The 77-68 was designed by Tim Moore and was offered for sale by Bear Microcomputer Systems of Newbury,

Berkshire Berkshire ( ; in the 17th century sometimes spelt phonetically as Barkeshire; abbreviated Berks.) is a historic county in South East England. One of the home counties, Berkshire was recognised by Queen Elizabeth II as the Royal County of Berk ...

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

from June 1977. It was among the first, if not ''the'' first, of British home computers and was featured in the launch edition of ''

Personal Computer World ''Personal Computer World'' (''PCW'') (February 1978 - June 2009) was the first British computer magazine. Although for at least the last decade it contained a high proportion of Windows PC content (reflecting the state of the IT field), the mag ...

'' magazine in February 1978. The Newbear 77-68 was both a home computer and a homebuilt computer, since it was designed to not only be used at home (hence a home computer), but also be assembled at home by its owner (hence a homebuilt computer).

Description

The basic 77-68 comprised an 8-inch square

printed circuit board A printed circuit board (PCB; also printed wiring board or PWB) is a medium used in Electrical engineering, electrical and electronic engineering to connect electronic components to one another in a controlled manner. It takes the form of a L ...

accommodating the microprocessor,

Static RAM Static random-access memory (static RAM or SRAM) is a type of random-access memory (RAM) that uses latching circuitry (flip-flop) to store each bit. SRAM is volatile memory; data is lost when power is removed. The term ''static'' differen ...

of 256 8 bit words and the bare essentials in terms of input/output and timing logic to make a working computer. The processor ran with an instruction cycle time of around 1.25 microseconds with most instructions executing in 3 to 7 microseconds. In the short time for which the 77-68 represented an economic and reasonably current technology for home computing, an active user group distributed designs for additional components such as memory cards, video display cards and

teletype A teleprinter (teletypewriter, teletype or TTY) is an electromechanical device that can be used to send and receive typed messages through various communications channels, in both point-to-point and point-to-multipoint configurations. Initia ...

interfaces which enthusiasts could, and did, construct themselves. It was even possible to run

BASIC BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming languages designed for ease of use. The original version was created by John G. Kemeny and Thomas E. Kurtz at Dartmouth College ...

. All the components to build the basic machine could be bought for around £50 with additional elements added later. This was a sensible approach at a time when, for example, 16K x 1 bit dynamic memory chips cost £7 each and 8 chips plus a significant amount of support logic were required to build a memory card.

Operation

The 77-68 was programmed in its most basic form with toggle switches and LEDs. With the microprocessor's operation suspended in "HALT" mode, memory words could be accessed and their contents observed in binary. The word could then be modified directly using an additional 8 binary toggle switches to specify the data required. Once a complete program had been "toggled in" using this method, the "HALT" condition could be removed using another switch and the microprocessor would look for an address at which to start executing the program in the last two words of the address space. This technique, called

Direct Memory Access Direct memory access (DMA) is a feature of computer systems and allows certain hardware subsystems to access main system memory independently of the central processing unit (CPU). Without DMA, when the CPU is using programmed input/output, it is t ...

was typical for many early computers using

volatile memory Volatile memory, in contrast to non-volatile memory, is computer memory that requires power to maintain the stored information; it retains its contents while powered on but when the power is interrupted, the stored data is quickly lost. Volatile ...

that did not retain its contents when the power was switched off. Even early

mainframe computer A mainframe computer, informally called a mainframe or big iron, is a computer used primarily by large organizations for critical applications like bulk data processing for tasks such as censuses, industry and consumer statistics, enterpris ...

s required their operators to "toggle" or "dial" in a bootstrap program by hand to get things going on power-up.

Capability

Although 256 words of memory seems extraordinarily small by contemporary standards, when "toggling in" programs by hand it seemed quite adequate. There was ample space to create programs that played music, sent and received

morse code Morse code is a method used in telecommunication to encode text characters as standardized sequences of two different signal durations, called ''dots'' and ''dashes'', or ''dits'' and ''dahs''. Morse code is named after Samuel Morse, one of ...

, operated data storage to media such as a

cassette player A cassette deck is a type of tape machine for playing and recording audio cassettes that does not have a built-in power amplifier or speakers, and serves primarily as a transport. It can be a part of an automotive entertainment system, a part of a ...

and even offered game experiences (though these required significant imagination by the user). Expanded with additional memory, the 77-68 was quite capable of running software such as the TSC

interpreter and users wrote software that offered a wide range of applications at a time when even

word processor A word processor (WP) is a device or computer program that provides for input, editing, formatting, and output of text, often with some additional features. Word processor (electronic device), Early word processors were stand-alone devices ded ...

s were a novelty and

spreadsheet A spreadsheet is a computer application for computation, organization, analysis and storage of data in tabular form. Spreadsheets were developed as computerized analogs of paper accounting worksheets. The program operates on data entered in cel ...

s were largely unknown.

User experience and legacy

For many home computer pioneers, primitive machines like the 77-68 offered a thrill that is hard to describe to a generation that has grown up with technology many times more powerful all around. The sense of being able to construct something from inert basic components, write a program and see a set of components that had been separate "come to life" in concert to do something small but useful was very exciting. This was a time when it was quite possible for a non-specialist to understand every aspect of the computer they had built and machines like the 77-68 offered a generation the chance to own and experiment with one for the first time. While the number of kits sold and constructed and the number of systems still in operation is unknown, one of the systems illustrated in this article is now in th
Museum of Computing

Swindon Swindon () is a town and unitary authority with Borough status in the United Kingdom, borough status in Wiltshire, England. As of the 2021 Census, the population of Swindon was 201,669, making it the largest town in the county. The Swindon un ...

References

{{reflist Early microcomputers 68xx-based computers