18kHz is indeed a cursed frequency for the OSSC. It is a simple line/pixel multiplier device and does not have the ability to do arbitrary scaling. If there is no way to "integer scale" the input frequency to something the output device can sync to then it cannot work

An update here. I logged a bug for this on OSSC github, and provided the dev with oscilloscope readings. He made a fix that should ship in the next firmware. I tested a beta firmware and now MDA works fantastic on OSSC.

I used the OSSC options to tint the output, and I was able to get a very sweet amber screen. I would highly recommend this setup for cheap MDA to LCD if you have already shelled for an OSSC. Building the cable is very easy.

wbahnassi wrote on 2025-03-15, 13:30:

An update here. I logged a bug for this on OSSC github, and provided the dev with oscilloscope readings. He made a fix that should ship in the next firmware. I tested a beta firmware and now MDA works fantastic on OSSC.

Thanks a lot for bringing this up on the OSSC github - I modded my version 1.6 OSSC today just so I can run firmware 1.12 which contains the MDA compatibilty fixes ... now my OSSC locks on to the MDA timings perfectly, but my monitor still can't handle it.

did you use any specific output settings on the OSSC to make your monitor accept the signal ?

KenjiUmino wrote on 2025-10-07, 01:02:

now my OSSC locks on to the MDA timings perfectly, but my monitor still can't handle it.

did you use any specific output settings on the OSSC to make your monitor accept the signal ?

I have two different LCD monitors.. 1080p and 1440p. The 1080p was only able to display on Line2X, whereas 1440p managed to display Line3x or 4x (don't quite remember). I suggest you try cycling through those to see which one syncs with your specific monitor.. I'm afraid there is no universal setting that would work for everyone. Each monitor is unique.. but newer, higher-res monitors with variable rates seem to be the best for these purposes.

wbahnassi wrote on 2025-10-07, 01:21:

The 1080p was only able to display on Line2X, whereas 1440p managed to display Line3x or 4x (don't quite remember). I suggest you try cycling through those to see which one syncs with your specific monitor.. I'm afraid there is no universal setting that would work for everyone.

I already tried stepping thru the different multiplier modes to no avail - I guess this monitor is just not the right one then.

You know what DID manage to sync?
This cheap VGA to (s)video converter I have kicking around ... this thing never ceases to amaze me.

wbahnassi wrote on 2025-10-07, 01:21:

Each monitor is unique.. but newer, higher-res monitors with variable rates seem to be the best for these purposes.

makes sense - they are made to support a wide range of refresh rates.

Since the firmware update, the OSSC even has an option to request VRR operation from the monitor if possible ... might help with "off spec" refresh rates (PAL sega consoles jumpered to NTSC output and vice versa)

I don't have any fancy variable refresh monitors myself but I bought a pair for my brother not too long ago ... just Imagine his face when I ask him if I can borrow one for a bit and tell him "I want to play some old games from the '80s on my 286 ... nooo, not those ugly cyan-magenta games ... Imma skip colors alltogether this time" 😄

I recently showed him how long it takes to start windows 3.1 from a quantum fireball on a 486 DX2/66.
His reaction was priceless 😁