MITS Altair 680b

MITS Altair 680b. The MITS Altair 680b was a significant early microcomputer kit released by Micro Instrumentation and Telemetry Systems in 1976 as a direct competitor to its own Intel 8080-based Altair 8800. Based on the Motorola 6800 microprocessor, it was designed to appeal to hobbyists and engineers interested in an alternative CPU architecture. Though less commercially successful than its predecessor, it played a notable role in the burgeoning personal computer market and the development of software for the Motorola 6800 family.

Overview

Introduced in 1976, the MITS Altair 680b emerged during a period of intense innovation in the microcomputer industry, following the landmark success of the Altair 8800. The system was conceived by Ed Roberts and his team at Micro Instrumentation and Telemetry Systems to capitalize on the growing interest in different microprocessor platforms. It was marketed primarily through advertisements in Popular Electronics and other hobbyist magazines, targeting the same community of computer club enthusiasts and electronics tinkerers. The design philosophy emphasized expandability through its S-100 bus, allowing users to add memory boards and peripheral interfaces from MITS or third-party vendors. Its release coincided with the development of crucial software, including early versions of Tiny BASIC adapted for the Motorola 6800.

Hardware specifications

The central processing unit of the Altair 680b was the Motorola 6800, an 8-bit microprocessor operating at a clock speed of 1 MHz, which competed directly with the Intel 8080. The base system included 1 kilobyte of static RAM, which was expandable to 8 KB using proprietary memory cards from MITS. Its backbone was the S-100 bus, an electrically modified version of the bus used in the Altair 8800, which became a de facto standard and was supported by companies like Cromemco and Processor Technology. Standard input and output were provided via a front panel with LED lights and toggle switches, while mass storage typically utilized an optional audio cassette interface. For expansion, the chassis could accommodate multiple cards for adding serial ports, parallel ports, or EPROM programmers, facilitating connection to devices like the ASR-33 Teletype.

Software and programming

Software for the Altair 680b was initially limited, with users often entering machine code manually via the front panel. A pivotal development was the porting of Tiny BASIC, a simplified dialect of the BASIC language, to the Motorola 6800 by figures like Tom Pittman and members of the Homebrew Computer Club. This interpreter was distributed through publications like Dr. Dobb's Journal and user groups, making the system more accessible. Other available software included a monitor program for debugging and rudimentary assembly language assemblers. The lack of a dominant operating system like CP/M, which was written for the Intel 8080, meant most programming was done directly in assembly language or BASIC, with storage on audio cassette tapes.

Impact and legacy

Although it did not achieve the iconic status of the Altair 8800, the Altair 680b significantly influenced the early personal computer ecosystem by popularizing the Motorola 6800 architecture. It demonstrated the viability of alternative microprocessor platforms to the Intel 8080, paving the way for later successful systems like the SWTPC 6800 and the Motorola 6809-based TRS-80 Color Computer. The machine fostered a community of developers who created software and hardware expansions, contributing to the knowledge base of the Homebrew Computer Club and similar organizations. Its use of the S-100 bus helped solidify that standard's importance in early microcomputing. Furthermore, the experience gained by MITS in producing and supporting the 680b informed the development of subsequent products before the company was acquired by Pertec Computer Corporation.

Variants and related models

The primary variant was the Altair 680, the initial kit version announced prior to the 680b. The Altair 680b itself was a revised model with an improved power supply and minor design changes. A related but more advanced system was the MITS Altair 6800, which was a fully assembled, turnkey computer aimed at business and educational markets. Other contemporary computers using the same Motorola 6800 chip included the SWTPC 6800 from Southwest Technical Products Corporation and the Sphere 1. Competing systems from the same era, such as the IMSAI 8080 and the Processor Technology Sol-20, were based on the Intel 8080, highlighting the architectural divide in the mid-1970s microcomputer market.

Category:Microcomputers Category:Motorola microprocessors Category:1976 introductions