Newbear 77-68

Last updated
A Newbear 77-68 under construction. The orange TV set is the VDU, the metal rack to the right contains the computer circuit boards and the keyboard is just visible, partially obscured by the rack front panel lying on the top. The 1950s blue oscilloscope to the left was an essential de-bugging tool 77 68 home computer under development.jpg
A Newbear 77-68 under construction. The orange TV set is the VDU, the metal rack to the right contains the computer circuit boards and the keyboard is just visible, partially obscured by the rack front panel lying on the top. The 1950s blue oscilloscope to the left was an essential de-bugging tool

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 microprocessor. Because it was designed to be assembled by its owner at home, it was also a homebuilt computer. The 77-68 was designed by Tim Moore [1] and was offered for sale by Bear Microcomputer Systems of Newbury, Berkshire, England from June 1977. [2] It was among the first, if not the first, of British home computers and was featured in the launch edition of Personal Computer World [3] magazine in February 1978.

Contents

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

A bare-bones Newbear 77-68 The blue and white block of DIP switches to the bottom left addressed a word of memory; the LEDs in the bottom centre displayed the contents of that word and the switches to the bottom right could be set to enter a program or data, one word at a time. 7768 cpu board.jpg
A bare-bones Newbear 77-68 The blue and white block of DIP switches to the bottom left addressed a word of memory; the LEDs in the bottom centre displayed the contents of that word and the switches to the bottom right could be set to enter a program or data, one word at a time.

The basic 77-68 comprised an 8-inch square printed circuit board accommodating the microprocessor, Static RAM 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 interfaces which enthusiasts could, and did, construct themselves. It was even possible to run BASIC. 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

A Newbear 77-68 front panel BEAR MICROCOMPUTER SYSTEMS 77 68 FRONT PANEL.JPG
A Newbear 77-68 front panel

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 was typical for many early computers using volatile memory that did not retain its contents when the power was switched off. Even early mainframe computers 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, operated data storage to media such as a cassette player 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 BASIC interpreter and users wrote software that offered a wide range of applications at a time when even word processors were a novelty and spreadsheets 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 the Museum of Computing, Swindon, England.

Related Research Articles

<span class="mw-page-title-main">Apple II (original)</span> First model in the Apple II computer series

The Apple II is a personal computer released by Apple Inc. in June 1977. It was one of the first successful mass-produced microcomputer products and is widely regarded as one of the most important personal computers of all time due to its role in popularizing home computing and influencing later software development.

<span class="mw-page-title-main">MOS Technology 6502</span> 8-bit microprocessor from 1975

The MOS Technology 6502 is an 8-bit microprocessor that was designed by a small team led by Chuck Peddle for MOS Technology. The design team had formerly worked at Motorola on the Motorola 6800 project; the 6502 is essentially a simplified, less expensive and faster version of that design.

<span class="mw-page-title-main">Motorola 6800</span> 8-bit microprocessor

The 6800 is an 8-bit microprocessor designed and first manufactured by Motorola in 1974. The MC6800 microprocessor was part of the M6800 Microcomputer System that also included serial and parallel interface ICs, RAM, ROM and other support chips. A significant design feature was that the M6800 family of ICs required only a single five-volt power supply at a time when most other microprocessors required three voltages. The M6800 Microcomputer System was announced in March 1974 and was in full production by the end of that year.

In computer architecture, 8-bit integers or other data units are those that are 8 bits wide. Also, 8-bit central processing unit (CPU) and arithmetic logic unit (ALU) architectures are those that are based on registers or data buses of that size. Memory addresses for 8-bit CPUs are generally larger than 8-bit, usually 16-bit. 8-bit microcomputers are microcomputers that use 8-bit microprocessors.

<span class="mw-page-title-main">Microcomputer</span> Small computer with a CPU made out of a microprocessor

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 (PCB). Microcomputers became popular in the 1970s and 1980s with the advent of increasingly powerful microprocessors. The predecessors to these computers, mainframes and minicomputers, were comparatively much larger and more expensive. Many microcomputers are also personal computers. An early use of the term "personal computer" in 1962 predates microprocessor-based designs. (See "Personal Computer: Computers at Companies" reference below). A "microcomputer" used as an embedded control system may have no human-readable input and output devices. "Personal computer" may be used generically or may denote an IBM PC compatible machine.

Tiny BASIC is a family of dialects of the BASIC programming language that can fit into 4 or fewer KBs of memory. Tiny BASIC was designed by Dennis Allison and the People's Computer Company (PCC) in response to the open letter published by Bill Gates complaining about users pirating Altair BASIC, which sold for $150. Tiny BASIC was intended to be a completely free version of BASIC that would run on the same early microcomputers.

<span class="mw-page-title-main">KIM-1</span> Single-board computer produced by MOS Technology

The KIM-1, short for Keyboard Input Monitor, is a small 6502-based single-board computer developed and produced by MOS Technology, Inc. and launched in 1976. It was very successful in that period, due to its low price and easy-access expandability.

<span class="mw-page-title-main">Altair 8800</span> Microcomputer designed in 1974

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 advertisements there, in Radio-Electronics, and in other hobbyist magazines. According to Harry Garland, the Altair 8800 was the product that catalyzed the microcomputer revolution of the 1970s. It was the first commercially successful personal computer. The computer bus designed for the Altair was to become a de facto standard in the form of the S-100 bus, and the first programming language for the machine was Microsoft's founding product, Altair BASIC.

<span class="mw-page-title-main">SWTPC</span> Defunct US electronic kit and computer producer

Southwest Technical Products Corporation, or SWTPC, was an American producer of electronic kits, and later complete computer systems. It was incorporated in 1967 in San Antonio, Texas, succeeding the Daniel E. Meyer Company. In 1990, SWTPC became Point Systems, before ceasing a few years later.

"An Open Letter to Hobbyists" is a 1976 open letter written by Bill Gates, the co-founder of Microsoft, to early personal computer hobbyists, in which Gates expresses dismay at the rampant software piracy taking place in the hobbyist community, particularly with regard to his company's software.

<span class="mw-page-title-main">Homebuilt computer</span> Computer assembled from available components rather than purchased as a complete system

A custom built or home-built computer is a computer assembled by its user and made of commercial off-the-shelf (COTS) components, rather than purchased as a complete and ready to use machine, also known as a "pre-built" or out-of-the-box system.

<span class="mw-page-title-main">Apple II Plus</span> Second model of the Apple II computer line

The Apple II Plus is the second model of the Apple II series of personal computers produced by Apple Computer. It was sold from June 1979 to December 1982. Approximately 380,000 II Pluses were sold during its four years in production before being replaced by the Apple IIe in January 1983.

<span class="mw-page-title-main">Microprocessor development board</span> Type of printed circuit board

A microprocessor development board is a printed circuit board containing a microprocessor and the minimal support logic needed for an electronic engineer or any person who wants to become acquainted with the microprocessor on the board and to learn to program it. It also served users of the microprocessor as a method to prototype applications in products.

<span class="mw-page-title-main">History of personal computers</span>

The history of the personal computer as a mass-market consumer electronic device began with the microcomputer revolution of the 1970s. A personal computer is one intended for interactive individual use, as opposed to a mainframe computer where the end user's requests are filtered through operating staff, or a time-sharing system in which one large processor is shared by many individuals. After the development of the microprocessor, individual personal computers were low enough in cost that they eventually became affordable consumer goods. Early personal computers – generally called microcomputers – were sold often in electronic kit form and in limited numbers, and were of interest mostly to hobbyists and technicians.

<span class="mw-page-title-main">General Instrument CP1600</span>

The CP1600 is a 16-bit microprocessor created in a partnership between General Instrument and Honeywell, introduced in February 1975. It is one of the first single-chip 16-bit processors. The overall design bears a strong resemblance to the PDP-11.

The MPT8080 "Microtutor" is a microprocessor trainer based on the Intel 8080 processor, developed by Limrose Electronics. It was designed in the mid-1970s to assist in the understanding of the then-new microprocessors.

<span class="mw-page-title-main">Single-board microcontroller</span> Microcontroller built onto a single printed circuit board

A single-board microcontroller is a microcontroller built onto a single printed circuit board. This board provides all of the circuitry necessary for a useful control task: a microprocessor, I/O circuits, a clock generator, RAM, stored program memory and any necessary support ICs. The intention is that the board is immediately useful to an application developer, without requiring them to spend time and effort to develop controller hardware.

<span class="mw-page-title-main">BASIC interpreter</span> Interpreter that enables users to enter and run programs in the BASIC language

A BASIC interpreter is an interpreter that enables users to enter and run programs in the BASIC language and was, for the first part of the microcomputer era, the default application that computers would launch. Users were expected to use the BASIC interpreter to type in programs or to load programs from storage.

Smoke Signal Broadcasting, Inc. (SSB), later known as Smoke Signal, was an American computer company founded in 1976 by Frederic Jerome "Ric" Hammond of Hollywood, California. The company earned its reputation by offering expansions for the Southwest Technical Products (SWTPC) 6800 microcomputer. It later manufactured its own line of computers, called the Chieftain. Though it remains little-known, Smoke Signal was an early and important manufacturer of multi-user computer systems.

References

  1. Kewney, Guy (19 October 1978). "Is there a Computer in the house ?". New Scientist October 1978. Reed Business Information. Retrieved 12 March 2011.
  2. 77 - 68: the Construction of a - Simple Computer - Using a 6800 Microprocessor. Bear Microcomputer Systems (1977)., ASIN: B001P844K8
  3. "A Mighty Micromite - The 77-68". Personal Computer World May 1978.