Programming is Addictive

The 6502 processor, as shipped in 1976, ran at 1 MHz. With its 8 bit words and 55 instructions, it is generally rated at 0.1 MIPS. As a comparison, the laptop I am writing this on runs at 2600 MHz, has 1GB of memory, and is rated at around 5,000 MIPS. Or perhaps a better comparison, the Walmart $199 special Lindows based Athlon offers 10,000 times the processing power and 128,000 times the memory for less than the cost of the Kim. And a hard drive will beat an audio tape recorder for mass storage any day.

Once I had a computer of my own, I became obsessed with writing software for it. I began by hand assembling instructions into 6502 opcodes, looking each one up on the 6502 Reference Card. Soon, the common instructions were embedded in my brain, where they remain to this day. Once I had a piece of working program, I could save it to audio tape.

Within a few weeks, I had written a cross-assembler in APL in order to not have to hand assemble code all the time. I still had to type in the hexadecimal opcodes and do the debugging by hand, though.

In my spare time at work, I would scribble algorithms and lines of code on pieces of paper. After hours, I would huddle over a terminal and use the cross-assembler to generate 6502 opcodes for the Kim-1. At home, I would type in the opcodes and single step through the program. Corrections would be made by hand, assembling machine instructions in my head.

I had always wanted to create a chess playing computer. Years before, I had dabbled with some homebrew hardware, a tape recorder, and a teletype machine to create a "computer" capable of playing a few moves of standard openings. Moves took minutes to retrieve from tape.

Now, the same old Model 15 Teletype was called back into service and connected to the Kim-1. It generated dumps and listings to help me debug the programs I was writing. The hexadecimal dump at the back of the Microchess manual was printed on this old 1930s technology baudot code printer.

When running, the Model 15 made a thundering noise as the head klunked across the page, typing letters one by one. To save us from eviction, it sat on a 12 inch thick foam pad, which lessened the transmission of vibrations to the floor below. The smell of hot machine oil and ozone filled our apartment when it was printing.

The Computer History Museum in Mountain View, California has one of these old machines on display.