It's time to create a proper diagnostics software for MSX

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Por maxis

Champion (512)

Imagen del maxis

02-08-2017, 00:09

IMHO, BIOS TEST ROM replacement is a good option, since it needs to work in a very harsh environment:
- No RAM;
- No/faulty slot/subslot logic
- Faulty buffers
- Faulty interrupt control
etc
Also Z80 has enough registers to run the most of the tests completely without RAM. Just on registers.

On the other hand, test ROM cartridge requires a lot of MSX functionality being already up and running, including the SLOT/SUBSLOT selection logic, bus drivers etc. Test ROM cartridge is required for endurance testing or performance verification.

tvalenca wrote:

So, I agree with @wernerkai, we need a hardware+software approach. A Small micro controller would check all those signals and report any "architectural fault" before BIOS could reach the slot and execute the test program. And if we have bad RAM chips, the cartridge RAM would allow the machine to finish booting normally and allow full Main-RAM tests.

However, for the signal integrity on the slot bus, the mentioned above microcontroller will require a fast multichannel A/D converter (simpler to have an oscilloscope a la maison).

For the busted machines, the BIOS ROM replacement seem to be a good option.

My two cents is that we need TEST BIOS ROM for very basic check and TEST ROM cartrige for production line test. It's pity, that POST check wasn't included into the original MSX BIOS.

Por Louthrax

Prophet (2435)

Imagen del Louthrax

02-08-2017, 00:51

Just some ideas here on this subject that is quite interesting:

I would maybe not go so far and say that none of the common faults can't be caught by software (no VDP INT generation or faulty VDP behaviors can be checked, also some basic slot-switching functionnalities can be checked without too much assumptions), at least if the testing software can be started. But I'm pretty sure that if the cartridge software is located in a ROM, and that if the VDP has no INT signal (or is simply broken), the ROM code will never be executed (specially on MSX 2 with the scrolling logo). Too bad we can't "shortcut" the BIOS slot and put the testing software right at boot time from a cartridge slot...

So I agree that some hardware checks could be useful, specially if the MSX does not boot at all. Not sure exactly on how to perform these tests, but I think that the extra testing-hardware here will need to be controlled by the testing-software anyway? Doing sophisticated tests (accessing slots / subslots for example) with only hardware might be tricky (micro-controller will have to mess with the slot selection / data / address buses?).

About the BIOS checksum it could just be displayed, and the user will have to check if it matches existing values? (ah well, if the VDP is working...)

Ideally the price of that cartridge should not be too high (most people won't want to invest too much to repair a single MSX). I think a 50€ or more cartridge will have a very restricted audience (people having 2 or more defective MSX machines and enjoying investigating and repairing).

Por Louthrax

Prophet (2435)

Imagen del Louthrax

02-08-2017, 01:21

maxis wrote:

IMHO, BIOS TEST ROM replacement is a good option, since it needs to work in a very harsh environment:
- No RAM;
- No/faulty slot/subslot logic
- Faulty buffers
- Faulty interrupt control
etc
Also Z80 has enough registers to run the most of the tests completely without RAM. Just on registers.

Agree with everything here, but that will require users to unsolder (on machines that are not socketed) / flash / replace ROMs. Not everybody has the tools or the practice to do that (I remember the first time I tried to remove a ROM chip and damaged several legs!).

I think we also really need a simple "ROM version" that can be flashed to any existing MSX ROM device (most of us already have some, and some of these devices have embedded RAM), so that when a user posts a question about a hardware problem, we can just instruct him to first run that software and report what's happening here on the forums (LEDs flashing, messages displayed if VDP still working, etc...). If no LEDs are flashing, that means the ROM code is not reached, next step will be unsoldering or replacing the BIOS ROMs and use the "BIOS version". If this BIOS version shows no signs of life (no LEDs flashing), then some hardware investigations will be required (or maybe just then invest in a cartridge with the dedicated test-hardware... could be the "Hardware version").

Thinking about those different approaches (at least "ROM version" and "BIOS version"), probably a great part of the code can be shared.

Por Grauw

Ascended (10679)

Imagen del Grauw

02-08-2017, 01:34

Louthrax wrote:

I would maybe not go so far and say that none of the common faults can't be caught by software (no VDP INT generation or faulty VDP behaviors can be checked

Bad VRAM is pretty common, it could even go so far to tell which RAM chip is damaged. Then again a photograph posted here will quickly identify the problem as well.

Also the mapper issue I had with my CX5MII could be detected (it booted all the way into Basic).

Por meits

Scribe (6530)

Imagen del meits

02-08-2017, 02:36

Noob here, totally, but what about a cartridge which is connected by USB to a pc which runs the diagnostic software?
Just an idea. Please don't kill me if it's a rediculous idea Running Naked in a Field of Flowers

Por tvalenca

Paladin (747)

Imagen del tvalenca

03-08-2017, 03:34

Meits wrote:

Noob here, totally, but what about a cartridge which is connected by USB to a pc which runs the diagnostic software?
Just an idea. Please don't kill me if it's a rediculous idea Running Naked in a Field of Flowers

Not ridiculous. Interesting thou.

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