In testing my latest iteration of an RGB to SVIDEO/composite board, I managed to toast my 2068. Symptoms point to fried RAM chips, according to an article on DIY fixes to the 2068, so I’ve ordered replacements.
The circuit boards above, from left to right, are a buffered 2068 expansion bus, an attempt to make a SD card based file storage solution and a board that will bypass the internal ROM (home and EXROM).
Buffered Expansion
I have several projects I want to hook up to my 2068 and I don’t particularly feel like making them all feed-through, like the old devices made for Timex computers. Instead, I’ve made an expansion board that allows for “cards” to plug in.
The first version I made is just straight through: there’s no buffering of any of the signals. The problem with that approach is almost every expansion card would need its own signal buffering.
Based on some work by Charles Bothner, I have fully buffered the address and data busses, along with a few other signals.
The address bus is one way; the data bus is bi-directional, driven by the /RD line.
SD Card file storage
I don’t have the patience for tape that I used to, so I’m working on a device that’ll use the commands built-in to the 2068 to save/load to SD cards. It has a Teensy 3.5 to do all the heavy lifting.
I’m calling it the 2065bis.
ROM Bypass
Bill Pedersen did a lot of research and work to improve the 2068. If you read his articles, you’ll see he was really enthusiastic about getting the 2068 to a state where it delivered on its potential.
One of those areas was a ROM bypass tool to facilitate developing correct Home and EXROM images. Larry Crawford worked with Bill on some of his projects and this is a PCB from one of them. It allows bypassing the internal ROMs and using static RAM and EPROMs.
As soon as I get my 2068 back in working order, I’ll be able to test boards and start working on these projects again.
