I first need to apologize for this account name, I somehow got stuck with it a while ago. Yeah.
So here's my situation. I have an EPOX 2themax EP-9NPA+SLI Socket 939 nForce 4 SLI motherboard. It's from 2005 and is the feature of my newest period accurate build. (My previous being my currently listed machine).
It has an AMD Athlon 64 FX-57 (labeled as an FX-55, but reports as an FX-57 for whatever reason, idk not complaining) and 1GB of DDR400 (to be upped to 4GB).
My graphics cards are dual nVidia GeForce GTX 7800 512MB editions as well.
If you look at the listing on Newegg: https://www.newegg.com/Product/Product.aspx?Item=N82E16813123246 you can see an oddity that was quite common on nForce 4 SLI builds. There is a jumper card in between the 16x slots that switch it from having the first slot being a 16x slot to both slots being plain 8x slots.
My issue is regardless of how I set it up, my second 7800GTX never gets detected in Windows XP. I've tried using Forceware and the plain GeForce drivers from years apart with no luck. It doesn't appear in device manager, and doesn't work with other graphics cards, or just having one in there. I have confirmed both cards work by swapping them out. I am using an SLI bridge, and it doesn't appear to be damaged in any way. Both cards are powered, and fans are spinning. My PSU (A brand new 650W Corsair unit) is perfectly fine to power both cards.
I think the problem may lie within the jumper card. If you look at the image, it's held into the slot with that plastic hook, but the hook appears to not have any real way to hold the card in. It's very loose and can wiggle around when insterted. Either way I have tried to secure it many different ways, but it still doesn't work.
There doesn't seem to be any BIOS options to change stuff around. I don't have the manual as resources for EPOX board are actually harder to find than resources for DataExpert boards.
Any help would be appreciated. If you need any more info on my setup just ask.