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

Guardian (3541)

25-06-2017, 14:49

I challenge the MSX developers to write a proper diagnostics ROM to be used by the community in a simple cartridge or that could be loaded into a flash cartridge (MegaFlashRom, Carnivore). The ROM should be max. 64k in size and should not require a mapper.

The ROM should be able to test:

- RAM
- VRAM
- RAM mapper functions
- PSG
- FMPAC (internal)
- VDP (screens, colors, pallette, fonts, sprites)
- keyboard (keys + lights)
- attached peripherals (joystick, printer)
- board's components (z80, MSX Engine, VDP, PPI, RTC, etc)

Because during a diagnostics the video or audio may be not functioning properly, its good to first ask a user to confirm that he sees the screen output and if he hears the beeps. If there's no video, the RAM+mapper+VRAM tests should run automatically and the feedback should be given by a series of beeps. If there's no video or audio, the feedback can be given by flashing a CAPS light.

We celebrated 30 years of MSX already, but we still have no proper diagnostics cartridge like Commodore guys have (Dead Test cartridge). We have TETRAM.ROM, which is great, but very simple. The TESTMAP.COM is detailed, but can be run only from DOS. Are there any other programs to test MSX? I don't know any.

So, I challenge the hardcore MSX developers to write the proper diagnostics software. As our MSXs are getting older and older, we will see a lot of malfunctions of our beloved computers within next few years. And a diagnostics cartridge will help to bring them back to life by detecting the source of the problems.

By Sandy Brand

Champion (295)

25-06-2017, 16:16

Maybe useful info:

Philips released some hardware test cartridges back in the day, but perhaps those are only geared specifically to their hardware setup?
http://msx.hansotten.com/special-msx-hardware/philips-test-cartridges/

Seems like there are test cartridges for MSX 1, MSX 2 and disk-drives:
http://msx.hansotten.com/technical-info/rom-dumps/

By wernerkai

Champion (357)

25-06-2017, 21:59

I strongly agree. I have 30 MSX machines here to fix

And I am a bit busy/lazy to deal with my logic analyzers...

Why not to use LEDs to show +5VDC power level, reset, clock ? Maybe a 7-Segment display to show some error code. The cartridge may include a terminal/LEDs for logic probe, so users without a scope can verify some signal activity.

Even maybe a MCU with an LCD Display, to verify proper activity in the bus, test stuck bits.

The Brazilian MSXs Expert 1.x and Hotbit 1.x have a jumper to enable /BUSRQ. This signal also disable the Z80 buffers, so you can plug an external Z80 onto the slot...

By Wierzbowsky

Guardian (3541)

25-06-2017, 22:25

Sure, something like that would be nice, but it requires serious hardware development. Statistically there are more programmers than hardware developers, so making a diagnostics software for obvious problems would be more preferable.

Speaking of hardware: I like those PC diagnostics cards:

https://www.aliexpress.com/item/New-Arrive-PCI-ISA-Motherboa...

By msxholder

Champion (399)

25-06-2017, 23:30

Sony,Spectravideo,Toshiba and Canon had for their MSX's Test cartridges.
For testing a MSX where to start ? Check the power supply.
Reset first and then Clock if it is a msx ,msx2 or higher it is generated different. There for each system an other aproach.
So Video ram next ? The msx (1) can operate perfecly without video.
What next Z80 or user ram or main rom? Remove them and replace. Or have we to check for a short in the adreslines or data bus or even control lines.(read,write,i/o,mem and refrehs and so on. Replace buffers..
Is the PSG faulty or the PPI .Delete them and buy other new etc etc.
The most frustating is the system controller.
That's making it problematic.

By msxholder

Champion (399)

25-06-2017, 23:32

By fubukimaru

Resident (46)

27-06-2017, 00:04

Wouldn't it be useful to implement the video-less output with something like Joy232?

https://github.com/Danjovic/Joy232

It's not really hard to build a cable for this, and a TTL-USB is really cheap on the internet. This way you'll have text diagnosis over serial.

By Grauw

Ascended (10682)

27-06-2017, 09:02

Speaking as an end user, a programmer; I prefer not to build anything, or order extra cables on the internet (for which I'm sure there are no drivers for MacOS). I prefer to just flash my MegaFlashROM and use caps lock or sound for diagnosis if the screen doesn't work. Or otherwise use one of my existing hardware, e.g. MIDI from the Music Module (but not everyone has that either).

By Lord_Zett

Paladin (807)

27-06-2017, 10:18

dontforget the diskdrive timings software! there was a philips cardrige you realy need to fix drives.

By Louthrax

Prophet (2435)

27-06-2017, 11:42

Lord_Zett wrote:

dontforget the diskdrive timings software! there was a philips cardrige you realy need to fix drives.
so

Curious about that. What was that cartridge checking exactly? Did it allow you to adjust things on your disk drives?

By tvalenca

Paladin (747)

01-08-2017, 23:20

That's a great idea, but i'm having trouble thinking on a software-only solution.

Problem is: no MSX is capable of booting without RAM. If you have a faulty RAM, no ROM cartridge would boot at all. But a Diagnostic cartridge could have enough RAM to allow booting (16k between $C000 and $FFFF) and any faulty MSX would boot up even if it has no RAM.

Also, most of the common faults on a MSX prevent it from booting. Faulty VDP (no INT generation), faulty slot-select logic, faulty DRAM refreshing logic, faulty RESET logic, just to name a few that I've seen while repairing my own msx. NONE OF THOSE faults would have been caught by a software-only solution.

Lastly, Most of those tests rely on checksums to test BIOS accurateness. Problem is: on every other 8-bit platform, there is only one (or just a few) ROM versions, while on MSX we have at least one version for each MSX model. It would take a lot of space just to catalog all those checksums.

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.