Sorry, I can't find a way to edit my original post. I did want to describe some of the steps I've taken to troubleshoot already.

Firstly, the drivers are those that were included in the floppy disc with this new old stock card. It hasn't been used in a computer before me.
BUT so far I've:

Replaced my VGA cable (I was using one with the sync pin removed originally since the computer's built in video output did not have a slot for that pin) with a standard one
Tried every variant of the drivers that are on that disc
Tried normal VGA (great but low res and only 16c)
Tried the SVGA 800x600 (also great, but only 16c).

Try the SVGA modes in DOS, eg. with X-VESA - https://ftpmirror.infania.net/pub/pc/utildiag/xvesa102.zip

The most important part is the "Test VRAM reliability"...

Grzyb wrote on 2025-06-19, 18:46:

Try the SVGA modes in DOS, eg. with X-VESA - https://ftpmirror.infania.net/pub/pc/utildiag/xvesa102.zip

The most important part is the "Test VRAM reliability"...

Thanks for your reply. I'm attempting to run x-vesa.com and what happens is:
- The bios boot screen for the graphics card shows up for a second as if I've restarted the computer
- I just get a blinking cursor and can't use any commands

What about VBETEST.EXE from some version of UniVBE/SDD ?
Eg. UniVBE 5.1a should work fine with Trident 8900D.

Grzyb wrote on 2025-06-19, 21:08:

What about VBETEST.EXE from some version of UniVBE/SDD ?
Eg. UniVBE 5.1a should work fine with Trident 8900D.

I'm struggling to find a download source for UniVBE 5.1 - any ideas?

Such stuff should be easy to find at countless old shareware sites...
Anyway, see the attachment...

Grzyb wrote on 2025-06-19, 21:47:

Such stuff should be easy to find at countless old shareware sites...
Anyway, see the attachment...

I appreciate your help. I checked a few places that I knew to check (internet archive, some sites I found on Google, etc.) But did not find the correct version.

Strangely, after I installed this software I got the blinking cursor. Attempting to run vbetest.exe also gave me the blinking cursor.

I guess something is wrong with that card...
It would be a good idea to test it in another machine.
Also, check the jumper settings, especially things like "zero wait states" - it can improve performance, but can also cause problems.

Is it a card with internal VGA ROM or a separate ROM chip? Might want to try a different VGA BIOS, if possible.

A photo of the card in question would be useful. Are the RAM banks populated properly?
8900D can work in zero WS mode, but that means the chipset requires a mobo with properly working ALE signal. That being said a broken ALE usually prevents the system from booting properly at all with 8900D in the slot.

Grzyb wrote on 2025-06-20, 02:53:

I guess something is wrong with that card...
It would be a good idea to test it in another machine.
Also, check the jumper settings, especially things like "zero wait states" - it can improve performance, but can also cause problems.

Oh man, I really hope it's not that and is instead something I'm doing wrong. I did play around with Jumpers as you said, but nothing seems to have changed anything so far!

bakemono wrote on 2025-06-20, 08:59:

Is it a card with internal VGA ROM or a separate ROM chip? Might want to try a different VGA BIOS, if possible.

I've attached a photo of the card below. I'm not seeing anything that I could remove or replace without desoldering pieces, but am admittedly not as familiar with playing with hardware so much as software.

Deunan wrote on 2025-06-20, 13:20:

A photo of the card in question would be useful. Are the RAM banks populated properly?
8900D can work in zero WS mode, but that means the chipset requires a mobo with properly working ALE signal. That being said a broken ALE usually prevents the system from booting properly at all with 8900D in the slot.

Photo of the card and the only documentation I got with it, attached! The only jumper that I've changed on the MOBO is the bottom-most one of the photo labeled "jumpers." This one disabled onboard VGA signal and let me get a VGA image through the card.

Update, it took me an embarrassingly long time to notice the jumper at R16 for Zero WS mode, but neither closed or open has any effect.

For an LCD monitor, the card should be set to Non-Interlaced = J2 Open.

But I don't think it's the main problem here.
At this point, I would simply check the card in another computer...

Hi there! Thanks for your reply.

Unfortunately this is the only PC of this era I've got access to - everything else is either too old or too new or a macintosh. I did previously attempt to switch J2 to open, but had no luck. But what I did notice is that J3 switches between 8-bit and auto-select BIOS. I closed it just to see and it seems to be running perfectly now. 800x600 at 256c is working just fine!

Thanks y'all for your help. This is great.

I was just about to say that 8-bit option does not work well in 16-bit slot, but you already figured it out. Not sure why it's the default setting. J1, J2 and J3 should all be open in typical AT system with a modern NI monitor.