Graphic Cards won't work

[imported_Nacelle]

I've got 3 Athlon 64 motherboards. A 754 and a 939 w/ Via chipsets and the other is a 939 nvidia sli board. On the sli board, all 3 graphics cards will work in it. So the cards are good. On the Via motherboards, only the ATI graphics card will post. All I get is a blank screen, no signal, from the Nvidia cards. I've swapped ram and power supplys around, to see if that was the problem. What's weird is, Both motherboards worked with these same cards at some point in the past, before I started upgrading my main computer and swapping parts around. I'm stumped.

The cards in question:
Radeon x1950 pro
Geforce 7900 gs
Geforce 7800 gt

 

[yh125d]

Some cards don't play nice with certain chipsets. For example, my eVGA 7600gt doesnt work with an ATI radeon 200 xpress chipset. But I've never heard of any problems with Via chipsets, only with nvidia cards and ati chipsets, or ati cards with nvidia chipsets.

 

[imported_Nacelle]

bump

 

[imported_Nacelle]

edited my original post a bit to explain myself better

 

[Jiggz]

This could be a bios problem on the Via mobo. Did you flash the bios recently before the problem started showing up?

 

[imported_Nacelle]

I didn't flash the bios on either of them. I did clear the cmos when I started having problems.

 

[Matthias99]

Did you double-check that everything is seated properly and that all the required external power connectors are plugged in? It's stupid, I know, but it's better to start with the easy things.

I'm not aware of any issues with recent NVIDIA video cards not POSTing on VIA chipsets. Maybe it's an old issue -- could there be a BIOS update for the VIA boards?

 

[imported_Nacelle]

I've swapped out cards, memory, and power supplies so much. I couldn't have messed up all those times. I ordered an nforce4 motherboard from newegg and now, one computer is up and running, at least.