KIM-1 - History

History

MOS Technology's first processor, the 6501, could be plugged into existing motherboards that used the Motorola 6800, allowing potential users (i.e. engineers and hobbyists) to get a development system up and running very easily using existing hardware. Motorola immediately sued, forcing MOS to pull the 6501 from the market. Changing the pin layout produced the "lawsuit-friendly" 6502. Otherwise identical to the 6501, it nevertheless had the disadvantage of having no machine in which new users could quickly start playing with the CPU.

Chuck Peddle, leader of the 650x group at MOS (and former member of Motorola's 6800 team), designed the KIM-1 in order to fill this need. The KIM-1 came to market in 1976. While the machine was originally intended to be used by engineers, it quickly found a large audience with hobbyists. A complete system could be constructed for under 500 US$ with the purchase of the kit for only 245 US$, and then adding a used terminal and a cassette tape drive.

Many books were available demonstrating small assembly language programs for the KIM, including "The First Book of KIM" by Jim Butterfield et al. One demo program converted the KIM into a music box by toggling a software-controllable output bit connected to a small loudspeaker.

As the system became more popular one of the common additions was the Tiny BASIC programming language. This required an easy memory expansion; "all of the decoding for the first 4 K is provided right on the KIM board. All you need to provide is 4 K more of RAM chips and some buffers." The hard part was loading the BASIC from cassette tape—a 15-minute ordeal.

Rockwell International—who second-sourced the 6502, along with Synertek—released their own evaluation board in 1976, the AIM 65. The AIM included a full ASCII keyboard, a 20-character 14-segment alphanumeric LED display, and a small cash register-like printer. A debug monitor was provided as standard firmware for the AIM, and users could also purchase optional ROM chips with an assembler and a Microsoft BASIC interpreter to choose from.

Finally, there was the Synertek SYM-1 variant, which could be said to be a machine halfway between the KIM and the AIM; it had the KIM's small display, and a simple membrane keyboard of 29 keys (hex digits and control keys only), but provided AIM-standard expansion interfaces and true RS-232 (voltage level as well as current loop mode supported).

Not long after the KIM's introduction, MOS Technology, Inc. was purchased by Commodore International and production of the original KIM lasted for a while under the CBM label, before it was ended. Chuck Peddle started work on an expanded version, with a full built-in QWERTY-keyboard, cassette tape drive, and monochrome monitor display.

The monitor was driven by a new built-in display driver chip, meaning no external terminal was required. The ROM firmware was expanded to include the BASIC as well, so the machine was up and running as soon as the power was turned on. The result was the Commodore PET (4 kB RAM, discrete logic graphics), launched in 1977 – one of three historic home/personal computers to appear that year, the two others being the Apple II (also 6502-based) and the TRS-80 (with a Zilog Z80).