Progress
I managed to make somewhat working custom profile.
Now problem is I can't get any enhanced modes working. Logitech paintshow gives garbage and no pointer.
Also colors are weird in dos programs... does cga need some modes set in config.sys in dos 5?

... I'm using output from go 329 add on card.

Kekkula wrote on 2025-05-15, 17:35:

Also colors are weird in dos programs... does cga need some modes set in config.sys in dos 5?

Nothing should be necessary in config.sys. The M24 is compatible with CGA at the register-level. What exactly do you mean with weird?

One limitation is that the M24 does not support the undocumented cyan/red/white palette in 320x200 graphics mode. On the M24, that palette will be shown as cyan/magenta/white.

Well landmark speed test does not show the color bars, there is no text in checkit graphics tests, and bolded colors in edit screen are almost non visible.

I'm using at&t deb card device driver on my olivetti go 329 card... I think the cards are identical... also I'm using msdos 5... maybe the driver is for 3.2... and it's a possibility that the card itself is defective...
I did try my working xt-ide msdos 6 installation without the driver, games seems to work but edit would give scrambled screen.

:edit
it's the mouse driver 😞
Ctmouse 2.1 hangs system complaining about no ega support, strangly works fine with error on my euro-pc
Ctmouse 2.0 gives no error and works fine in games, but scrambles screen and hangs the system if you try to run edit.

You actually have one of those mythical DEB upgrades in your M24? Wow.

Well not much to do with it 😕
Got the machine mostly working with dos 5 install from my euro-pc. Don't know what the problem was with mouse drivers but now it no longer freezes.
I prefer this machine over the euro-pc because this has 640k ram and expansion slots, so I fitted xt-ide and picogus to machine, trade off is now I don't have plantronics mode.
For 16 colour graphics I just have to stick with my hp vectra e5 ega machine.

My M24 is dead (PSU RIFA went boom and I've not yet had time to replace), but IIRC the M24 used 25kHz output for its higher video modes. Could that be why they're not displaying correctly?

This machine keeps fixing itself 😀
Now landmark shows colour bars and checkit text in graphics tests.
But now I think I have wrong palette in rgbtohdmi, it doesn't show light colours. Should it show those in cga mode?
if I choose rgbi I have no brown and by choosing rgbi (cga) I get brown but still no light colours.

Wow!

DEB in action. Really wish I had this in my M28 which also supports it. I also have the original color monitor .

dionb wrote on Yesterday, 11:55:

My M24 is dead (PSU RIFA went boom and I've not yet had time to replace), but IIRC the M24 used 25kHz output for its higher video modes. Could that be why they're not displaying correctly?

That's probably also why my Dad's M24 didn't turn on anymore when I tried it a while back.

@dionb Is it okay if I reach out in a DM to inquire about more info on how to fix this? Thanks!

vetz wrote on Yesterday, 16:41:

Wow!

DEB in action. Really wish I had this in my M28 which also supports it. I also have the original color monitor .

It would be great if the design of the DEB could be reverse-engineered. Perhaps this could be done with some high resolution photos or scans of both sides of the board? Thanks!

@Kekkula M24 color monitors lack the circuit that IBM CGA and clone monitors had built-in to show "dark yellow" as brown. Instead, it appears as a mustard color. So maybe whoever defined the M24 profile for the RGBtoHDMI included this limitation on that profile, for emulation accuracy?

digger wrote on Today, 09:50:

[...]

That's probably also why my Dad's M24 didn't turn on anymore when I tried it a while back.

@dionb Is it okay if I reach out in a DM to inquire about more info on how to fix this? Thanks!

Given I haven't fixed it either, I'd suggest you'd have more luck with a separate topic here so others can participate.

In the case of mine it was pretty obvious - sparks, smoke and shreds of capacitor visible in the back of the PSU.

digger wrote on Today, 09:57:

@Kekkula M24 color monitors lack the circuit that IBM CGA and clone monitors had built-in to show "dark yellow" as brown. Instead, it appears as a mustard color. So maybe whoever defined the M24 profile for the RGBtoHDMI included this limitation on that profile, for emulation accuracy?

RGBtoHDMI doesn't have profile for m24. I had to make custom profile to get picture.
I set frequency to ~24khz and fidled with line length until I got stable picture.
One neat feature in rgbtohdmi is it supports composite modes with ntsc artifact colours.