MVS Diagnostic BIOS usage question - and a few other things

[rewrite]

So I downloaded and programmed the Diagnostic BIOS for the MVS as I have a few that need work and didn't know where to start. Unfortunately, one of them does nothing at all, and the other passes all tests but is still messed up.

However, the third one gives a VRAM error. And what I'm curious about is how to tell which of the two VRAM needs replacing without just guessing.

Also, I found a very useful pinout of all the connector pins on the 4-connector 4-slot motherboard while browsing around. Does the same thing exist for the 3-connector 4-slot? Or the 2-slot?

 

[Apocalypse]

So I downloaded and programmed the Diagnostic BIOS for the MVS as I have a few that need work and didn't know where to start. Unfortunately, one of them does nothing at all, and the other passes all tests but is still messed up.

That's the thing with diag ROMs/BIOS, there's only so much they can do. If the fault is basic then yes it will be detected. However for a RAM error for instance the BIOS can't determine if the RAM chip is faulty, the custom chip connected to it or traces in between.
That's great some people make them to make repairs more accessible to everyone (although I don't use them, with experience all the basic faults detected by the diag ROMs/BIOS can be quickly detected without them).

However, the third one gives a VRAM error. And what I'm curious about is how to tell which of the two VRAM needs replacing without just guessing.

My advice would be to change both as coupled RAMs tend to die at very short interval (I had the issue again recently on a Heated Barrel board).

 

[rewrite]

So I downloaded and programmed the Diagnostic BIOS for the MVS as I have a few that need work and didn't know where to start. Unfortunately, one of them does nothing at all, and the other passes all tests but is still messed up.

That's the thing with diag ROMs/BIOS, there's only so much they can do. If the fault is basic then yes it will be detected. However for a RAM error for instance the BIOS can't determine if the RAM chip is faulty, the custom chip connected to it or traces in between.That's great some people make them to make repairs more accessible to everyone (although I don't use them, with experience all the basic faults detected by the diag ROMs/BIOS can be quickly detected without them).

However, the third one gives a VRAM error. And what I'm curious about is how to tell which of the two VRAM needs replacing without just guessing.

My advice would be to change both as coupled RAMs tend to die at very short interval (I had the issue again recently on a Heated Barrel board).

Thanks! I'll just swap both out and see how it goes.

Here's hoping I can run across more info on the 3-connector 4-slot board (namely the connector pinouts), because otherwise it may just sit around until I find another one to swap top-boards with to see if that fixes anything. I've got 3 4-connector 4-slots, but only the one 3-connector one.

 

[Apocalypse]

You're welcome.
I think a 4-slot is able to boot up to the crosshatch pattern even if the top board is unplugged from the bottom board.

 

[rewrite]

You're welcome.
I think a 4-slot is able to boot up to the crosshatch pattern even if the top board is unplugged from the bottom board.

It will! And it does. And passes all the diagnostic tests. Hence my wondering where to go from there. I'm going to give it an even more thorough cleaning, maybe that will help.

The big one has no video and seems to be in watchdog. Can hear the audio click like it's resetting a couple times a second. It's a bigger project so I've set it to the side for now. Reading around suggests work ram, or the z80 as a good starting point.

Ordered the vram a week ago so the 2 slot should be fixed when it comes in. It was just a minor graphical glitch.