Wednesday, September 11, 2013
6800 Info from the Woz per Lionel Theunissen's Rig up and running the 6800
Woz's comments on Lionel Theunissen's A-1 rig running the 6800 cpu --
"I designed the computer for the 6800. The Apple I board even has an area for a dozen parts labelled "for 6800"…it also had to have these parts for the 6501, which was a barely cheaper version of the 6502. What these parts did was supply a faster harder clock signal to the chip. Otherwise, the pinouts of the 6800 and 6052 were compatible.
I could buy a 6800 for $40 as an HP employee. That's why I designed the computer for it. Then the 6502 got introduced for $25 ($20 for the 6501). I switched because it was better (in my judgment, with more addressing modes) and cheaper.
The Apple I ran on a 256-byte program, burned into 2 PROMs. We didn't have much memory density back then for these programmable chips. All you'd have have to do is to read my program (given away publicly) with the comments, and translate it to 6800 code. Tight, but doable.
The cassette board, for using a cassette tape drive to store programs, had a 256-byte program of its own on the board. In this case it was in one chip, as I recall. That too would have to be converted to 6800 language for a more complete project.
The next step would be to find some public domain 6800 BASIC and convert it to run in the memory addresses of this computer.
All-in-all, not too hard. But it's a special project worthy of commendation."
Posted by John at 1:30 PM