A little bit of googling and I came to the model name/number of my second Socket3 board, apparently "DX-6900 or 80486 Deep Green".

mashrien wrote on 2020-11-05, 05:52:

A little bit of googling and I came to the model name/number of my second Socket3 board, apparently "DX-6900 or 80486 Deep Green".

That board is also known as an M912 and I've found it to be a good one.
So the CL-GD5426 has no jumper information whatsoever, not even on the back?
I see the IDE chip on it is a Promise PDC20230B, which is a VLB one, that should be fast. I'd stick with that and figure out how to disable IDE on other cards (or move other cards to the second IDE channel).
I'm not sure why you are having that problem with the CT3600. It looks like that is a Plug 'n' Play card so it shouldn't conflict with booting from IDE as it shouldn't get assigned an address until configured through Plug 'n' Play.
It looks like the CL-GD5426 also has a floppy controller on it. I presume you aren't using it, so it must be disabled?
Maybe you could look up the pinout for that Winbond chip and trace pins back to the jumpers that control them.

You're saying the Cirrus Logic VLB video card would be a fast controller? I didn't even notice it was a Promise chip.
I figured having the CL be exclusive for video, and a separate controller would yield better over-all system performance. If that's not the case then I'ma just slam that CL back in and use that instead.
(Currently testing with a Trident TVGA 8900-CL. Not sure which would be faster.. the CL or this Trident.)

jakethompson1 wrote on 2020-11-05, 06:09:

So the CL-GD5426 has no jumper information whatsoever, not even on the back?

There's zero markings/indications of any kind on the reverse of the card, unfortunately.

@jakethompson1 I can't PM yet, still too much a nubile on ze forums. Hit me up on Discord if you've got it- @Mash#1955