KIM-1 – Retro Computing

Developed by Mos Technology. later acquired by Commodore, to show the possibilities of the 6502 microprocessor but quickly discovered as the first mass-produced personal computer. Easy to extend, lots of detailed documentation. With assembler/editors, first Microsoft Basic on cassette and even a Pascal compiler, it could do a lot. The first have an original Mos Technology logo, later versions have the Commodore logo on the board, small technical differences other than more recent 6502 IC’s without the infamous ROR omission.

This prehistoric computer has no “real” keyboard and no video output, program are entered by the small hexadecimal keyboard (located in the lower right part of the picture) and results are displayed on the small LED “screen” (it can display only 6 digits). It has a simple monitor that allows one to examine, modify memory, load and save paper tape, load and save cassette tape, run and debug programs through a ‘single step’ mode. The monitor works with the built in keypad and LEDs, or a terminal like the Teletype ASR33. This 20 mA current loop is easy to adapt to RS232C and so any videoterminal can be used.

The KIM-1 design inspired many designers of 6502 systems, mimicking either the unique LED and keypad setup or by having the same application and expansion connector
Notable are:
– SYM-1 Application and expansion connector, LED and keypad display, tape format
– AIM 65 Application and expansion connector, tape format
– MCS Alpha 1 LED and keypad display, tape format
– Elektor Junior LED and keypad display, tape format

Information on the KIM-1, also reachable from the menu on the right:

Prototype KIM-1

On team6502 I found a photo of a prototype KIM-1 at MOS Technology, Terry Holdt has this in his office.
The layout is different from the final product, everything seems to be present on this prototype.