twolazy
Veteran Member
I can relate, still have a few boards that are clean as new, and just refuse to show life... Do you have an eprom burner? Just to rule out bios corruption...
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IBM PS/2 Model 25 Not Posting, not sure where to start
- Thread starter Benson86
- Start date
twolazy
Veteran Member
Anyone know if RUUDS diagnostic works on that machine? It should in theory. Landmark might work too , need someone with more knowledge of these machines to verify.
modem7
10k Member
From what I see, the 8086 version of the Model 25 is XT class; suitability in that regard. The CGA card would need to be used.
Looking at the images of the 00F2092 and 00F2093 ROM's at [here], 00F2092 is even/low and 00F2093 is odd/high. Each ROM is 32KB sized and so probably of type 27C256. So the 8KB sized code for Rudd's Diagnostic ROM should repeated 8 times to create a 64 KB sized binary file, then that split into high and low files for two 27C256 EEPROM's. That is my educated guess.
Yes, it would be good for someone who has one of these machines to verify. Ruud's diagnostic could display something, but one of more tests may fail due to the machine not being "100% compatible".
( I remember a trade magazine testing the 'IBM XT hardware compatibility' of a number of well known XT clones of the time, and the IBM P/S2 Model 30 came in last !)
modem7
10k Member
If you did want to do that (for peace of mind) they should be measured out-of-circuit. Not necessarily "easy", but just cutting one leg is enough, say, half way up the exposed part of the leg. Do the measurement, then 'blob' solder the two cut leg ends back together. Measure via the capacitance setting on your multimeter, or some other device that measures capacitance.
modem7
10k Member
Have you seen something that indicates that the Model 25's IBM BIOS ROM outputs codes to a parallel/LPT port ?
modem7
10k Member
For a 1987 dated IBM BIOS ROM, one would hope so. Per [here], even on an IBM 5170 (IBM AT), a failure in the first 64 KB of RAM results in a 201 error being displayed, although a requirement for the 5170 is an MDA or CGA screen.
It would be good is someone with the same machine as yours would pull out the two SIMM's and report whether or not they see an error on-screen (or hear beeps).
BTW. I see RAM chips either side of the IBM BIOS ROM's. It could be that the RAM configuration is the same as that for the IBM 5162 - see [here].
Yes, David has a video on it here:
And he has been posting on my reddit thread about this machine. It's probably gonna have to be my next step so I can at least figure out where it failing.
dhau
Experienced Member
Is motherboard in model 30-8086 and 25-8086 the same?
I dont think they are exactly the same, but my admittedly rudimentary understanding of the PS/2 series seems to point that from a diagnostic perspective at least they are similar enough that I should be abel to get some idea where its failing in the boot process with the codes. It's only $10 for a reader so I ordered one, figured cant hurt to try since im not making much headway from other angles.
Update, finally got the post code reader in. Its not posting any codes whatsoever unfortunately. Idk the board just seems dead its really strange. I can't figure out why it would be completely dead and not even attempting to post if the board and everything is getting power. I know a dead cpu is pretty rare but would a dead cpu cause it to not post any codes?
Caluser2000
Banned
Can you pull the cpu and reset it a couple of times? Spay the empty socket and cpu pins with Deoxit or IPA between pulls/inserts.
I have retried reseating it a few times to no avail. Well, 8086's are cheap, I guess ill give a replacement a shot. If that doesn't work ill probably just move on from it at that point lol. Appreciate all the help so far guys
twolazy
Veteran Member
I have to agree here. I bought a post card off ali-express, and it almost shorted out my ISA bus. Wasn't till AFTER I received it, that the listing changed, and noted the isa side in fact does NOT work.
modem7
10k Member
Yes, but so would quit a few other chips.
As for POST codes: The CPU (described during my digital training days as a 'high speed moron') is reading programming code located in motherboard ROM, and 'blindly' following what the programming code is telling it to do. For example, output 55 hex to I/O port 3BC hex. So for any chance of POST codes to appear, the ROM/s need to be good, and any other chip involved in the process of the CPU reading code from the ROM's. Those other chips can be things like buffers, transceivers, various chips that do chip select decoding. And the reset circuitry needs to be working enough for the CPU to be properly reset at power-on.
I think that a set of replacement ROM's are worth a shot.
Do you guys know where I would go about getting a set of replacement roms for it? I dont own any flashing equipment, I know that might not be a bad investment at some point but can't really justify it right now. It's certainly something I would try if I knew where to get them.