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Also, check the surface of the disk for mold.

Agreed. After a bit of searching through PDF's I couldn't locate a schematic, but maybe more digging will reveal it.

The only thing I could find was this page in german: https://forum.classic-computing.de/forum/index.php?thread/14546-kennt-jemand-einen-rechner-namens-philips-p2500/&postID=192423#post192423

Welcome to Board #4! [Link to Original Thread / Board #3] Initially the address on the ISA slot wasn't reading correctly during ground I/O CH RDY procedure (simiar to Board #1) and as in Board #1 the address bus chips (U7 / U9 / U10) were not enabled. I took a look at U98 & U67. As in Board...

Has some fun programming in NASM, displaying bits & test patterns etc (the RDR asm is so well documented, it's practically a tutorial / clinic on how to write code) and I'm going to move on to the final board. Might come back to this one.

Did you also try the usual password suspects? Blank password, "password", "secret", "123456", etc.

Sounds like something powered by AI :) Good point, easy to do and worth a try Will do. I'm leaning towards putting a socket on that chip just to try another and rule out that it's glitching as those so often do fail p.s. using interrupts is there a way to arrange single-stepping the CPU one...

Ok yea, nevermind. I created a version of the ROM that loops testing the first byte of memory, but I don't think its stable enough to get a read of what's going on before it crashes.

On a side note I have RDR running in pce-ibmpc to test some code modifications.

I know what you mean. Let me expand a little bit on the test. Sometimes RDR doesn't crash, and reports a failure. The test code would simply test RAM address 0000:0000 in a loop. I guess the question is would the loop crash the board. I don't know. If the board doesn't crash testing...

Sounds good. Glad you have some more ideas because pulled U13, U15 & U16 tonight. They check out ok as far as I can tell. To check the signals on all these IC's, do you think it's worth trying to develop a custom ROM to reproduce the issue? Something I could run on a working board, and...

I created a new RDR ROM, but RAM tests and crashing persist CPU to ROM would be U15 / U16, and ROM to CPU would be U13 correct? If that's the case i'm going to start pulling and replacing those chips one at a time. Seems like 1/3 of the chips on this board are fried anyway :LOL:

I thought U12 might be the issue, but after setting up a capture with the LA, it looks fine. Out of ideas at the moment. Board is unstable, 1 out of 3 RDR runs the board crashes at the first 2KB RAM test. Largest address failure I've seen is b.

Replaced U101 and now all RDR 8253 timer channel tests pass. On to the RAM now. I'm a bit surprised the first 2 KB of RAM always fails after TEST5060 & TEST5067 passed on the LA. Sometimes it crashes RDR as well.

TEST5060 & TEST5067 Look good so RAM should be good to go, however RDR now consistently fails all the 8253 timer channels. Even though the 8253 is a solid IC, I had myself convinced it could be faulty. Socketed and swapped out with known good, timers still fail so ruled that out. I started...

I was testing for a short between MA6 and a data line when I found one of the grabbers was creating a short between MA6 & D7. I'm not sure how that short was only in half the previous capture, but I was able to get a clean capture after I fixed that. I'm going to run some more tests, because...

Ran another capture using TEST5060 and i'm seeing something odd, everything looks good except the first write Address out of each series of four operations is "BF" instead of "FF." Consistent, and happens every time:

I wired up the board with the LA. Data and Address buses look reasonable, but WE is nowhere to be found. I double checked it's connected to the correct probe by grounding it, and confirming it dropped LOW. Going to trace back Write Enable, i'm guessing the signal crosses through the...

I ran TEST5065, confirmed A0 to A19 are toggling/pulsing, XA0 to XA12 are toggling/pulsing. I also tried some chip piggy back on U62 and U79, no change in RDR.