Mike's PCjr Page

I loved Procomm 2.4.3 and I used it a lot. It's still my go-to terminal emulator for DOS, but I wish I had a version that supported 43 or 50 line screens. Anyway, to your question ... Procomm does not know about the PCjr so it doesn't program the baud rate divisor on the UART correctly. This is gene...

Ok - I'm glad I asked for a picture because I just cracked a machine open and mine is different:
I need to open up a few more machines until I find one that matches yours ...

Can you take a picture of the board, in particular the affected area? There were a few different revisions of the board and you want to be sure.

Also, look for other signs of damage. It's unlikely that the resistor just gave up on its own ... something else is probably wrong as well.


-Mike

Ok, I have an happy update ... it's fast. My benchmark was bad. On writes it was counting the time for DOS to create a file. It was also probably artificially slow, as DOS has to do housekeeping to keep modifying the FAT as a file grows. I made the following changes: When doing a write test, seek to...

The PCjr is terrible at keeping time during disk I/O tests - I suspect the BIOS is disabling interrupts for too long. I usually have to do my timing tests with a stopwatch, which is sub-optimal. I made my timing test slightly more accurate by reading the RTC clock at the beginning of the test and th...

I really don't know ... I know what Disk-On-Modules do and what SSDs do, but Compact Flash had too many price points to rationalize about what each one was doing. Especially on the older, smaller cards that were designed for digital cameras and not as replacements for hard drives. Take the web serve...

OT, but a quick look back into history: The memory window was one of the design requirements ... At the time the XT IDE had the same I/O register layout as an IDE controller, but it was not really compatible with IDE because any command that needed to read data was broken by the requirement to do tw...

Well, that's the problem ... the jrIDE uses a memory window, not I/O registers. I talked Alan into doing that because of REP MOV. When I measured the SD Card to IDE adapter that eventually flaked out on me I was getting 300KB/sec reading and 220KB/sec writing. And I'm pretty sure that even my 20 yea...

2022-04-13: Please read to the end of the thread .. the performance difference has been explained and resolved. So I gave up on SD Cards because they are fairly cheap devices to begin with, and getting them to work on IDE was kind of "janky." For my latest experiment I used a StarTech SAT...

I've changed my mind ... I purchased a second adapter (https://www.amazon.com/dp/B07YFPX7JB) and I couldn't make it work at all. And my first adapter also wasn't working either, which really irritated me. So I had a marathon debugging session. Using a jrIDE and a modern-ish Athlon system with built-...