Apple I

Drennan on the KIMSI

Richard Drennan
4590 Oberlin Avenue
Lorain, Ohio 44053

Dear Joe:

KIMSI Connections

This paper shows the connections between the Apple 1 computer and the extension (expansion) card for the Kim-1 computer.

KIMISI Connections sheet


This board connected to the Apple 1 via the 44 Pin Bus and allowed S-100 cards to be connected.

The MOS Technology Kim-1 was a 6502 cpu based single-board computer with 1k of memory and a keypad for input.

Homebrew EPROM card

Apple I - eprom card back

Apple I - eprom card front Apple I - eprom card back 2

Joe writes:

"I built an EPROM card to use in the 44 pin bus in my Apple 1 computer. It had on it two 2716 EPROM's. The 2716 was a 2k memory chip. I had a new monitor and a dis-assembler on the chips. To use this card I had to first unplug the two Apple Proms on the motherboard. As you can see I did not solder the sockets, but wire wrapped the card instead."

44 Pin Bus Advertisement

44 Bus Motherboard Advertisement

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44 pin bus catalog cover

44 Pin Bus

The 44 Pin Bus Motherboard connects to the 44 pin edge connector on the Apple I and provides ten slots. Joe cut the board down to three slots and put three connectors on it due to space limitations in the cabinet.

The Cassette and its Interface

Apple I BASIC cassette

Apple I cassette interface front Apple I cassette interface back

Apple I recorder

Entering data by hand is a slow and cumbersome process. Storing the code on some sort of media, even if that media is merely a cassette tape, is far more efficient. As a consequence, the Apple-1 Cassette Interface was a popular add-on. Many programs were available from Apple on cassette, such as BASIC, Dis-Assembler, Blackjack, Hamurabi, and Luner Lander.

Motherboard Close-ups

Apple I - 6800

The 6800 area of board.

Joes tell us, "If I remember right, you pulled the 6502 chip and put in the 6800 cpu and all the parts and you had an Apple I based on the 6800 cpu instead of the 6502 cpu. I also believe that there was a law suit by Motorola who had the 6800 chip because MOS Tech who came out with the 6502 chip were all engineers who left Motorola and helped on the 6800 cpu and the 6502 cpu could use all the instructions that the 6800 had and was faster."

Briefcase Apple I

Back in 1977, Joe stored his Apple 1 in the below pictured briefcase. The transformer and main boards were mounted and the keyboard was also stored inside. All you had to do was pick up the briefcase and your monitor (TV) and you had a portable computer that could go anywhere.


With every componet coming from a different manufacturer, it was impossible to assemble the entire Apple I all at once. Joe spread everything out on a work desk in the basement, and assembled the system as the pieces came in.

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