Mike's PCjr Page

I updated the public SVN. Sorry for the delays. The B version adds two more by-pass caps on either side of the board, adds support for a crystal resonator and battery holder so the non-potted Dallas clock chip can be used (or the potted if desired), and improved some silkscreen markings. The B+ vers...

Apparently I just missed Kevin when I was in Dallas on Sunday. :( Just note the B board also needs a tweak. I forgot to put soldermask relief around the crystal oscillator holes. I had to scrape it off all 100 boards of that run. I've recently tweaked the Rev.B art a little to add those mask holes, ...

You could probably get by jumpering up the power supply cables from one if you didn't have any extra side cars. RAM expansions can overlap without much issue. Both RAM parts mapped to the same addresses will latch and drive the same data. But since they have different response timings, there may be ...

As I said, I'm happy to do it. If it were just one bad trip to the post office (or 2 in this case), I'd be building boards every day. But there are a lot of little things that add up. I'll come back to PCjr stuff soon. But from now till the end of the year I'm swamped with a contract job and couple ...

Sexy

Out of stock.

The sound card project isn't PCjr related atm. More on that next month. Yeah, I'm not sure why more people didn't adopt a memory mapped approach. Could still be done with 74xx logic. It's just the IDE data register at 512 consecutive addresses so one can do a 'rep movsw' and not have any instruction...

So the boards are selling out within a few hours of posting a new listing of 8 or more. I posted one last night and emailed/messaged a few people that asked be about them in the past. I don't think all of those people had a chance to buy one. I have 10 actual blank PCBs left (+ connectors) and just ...

I'll document the project on my site this week and update the link here when finished. I have some boards made already + some quantity of parts. I can send what I have to anyone willing to take up the effort. They are SMT however with a TSSOP-20 (16v8), by-pass cap (0603) and a single dip-switch. Th...

Lots of RAM, I/O, and Bungholio Marks!

https://www.retrotronics.org/images/ultimate_jr.jpg