Complex Motherboard Question [ASUS A8N-SLI Deluxe]

[xerodok]

I'm going to make this sound as less complicated as possible in hopes to find someone else that has had similar problems or can tell me yes or no.

I have a ASUS A8N-SLI Deluxe motherboard, it's from an old scrap pile of parts that I'm converting into a FTC miner. The end goal would be having two PCI-e graphics cards running on it. It's properly powered (750W PSU) and everything boots properly.

The 7950 I have attached to it's primary PCI-e slot works perfectly, however, when I add another to the secondary PCI-e slot, its fully powered, and is detected as being there, but, appears as an 'unknown device.' It also doesn't show up in Catalyst. I'm not trying to use SLI, crossfiring, or anything of that nature, they both would be independent. I know it's geared toward SLI/NVidia, but I figured it would work if I wasn't doing anything special. I'm running all of this under Windows 7 Professional x64. Both the graphics cards are good because they both work in the primary PCI-e slot.

Can I use two AMD GPU on this board? Any thoughts/input?

[Sonomaa]

its an older tier mobo so it might not actually detect both cards if one is forcing the PCIx to x16, it might have a specific SLI mode that makes it detect 2 video cards
if the bios has an option to make 1 of the slots x8 that will probably let the board detect 2 cards at x8 speeds. a lot of those mobos couldnt support 2 cards at x16 but only split the bandwith between 2 x8 paths
its also an nforce board so it might need a bios update to detect more powerful video cards in 2 slots properly

[xerodok]

its an older tier mobo so it might not actually detect both cards if one is forcing the PCIx to x16, it might have a specific SLI mode that makes it detect 2 video cards
if the bios has an option to make 1 of the slots x8 that will probably let the board detect 2 cards at x8 speeds. a lot of those mobos couldnt support 2 cards at x16 but only split the bandwith between 2 x8 paths
its also an nforce board so it might need a bios update to detect more powerful video cards in 2 slots properly

There is a weird bridge on the motherboard that you can switch between 'Single GPU' and 'Dual GPU' but, using Dual GPU doesn't do anything. I tried taking it out too. I'll try to flash the BIOS again but, I don't see anything that configures/modifies the PCI slots. I'm guessing they are split bandwidth, which is stupid of me not to think about before hand.

Pic related:

[Isiolia]

Even a modern Z87 board will only do 8x for SLI/Crossfire without extra stuff. Part of the draw of the X-series chipsets is that the greater PCIe lane count means they can do better than that.

I think the probably you're seeing here is that Crossfire is deliberately not supported by the nForce4 chipset/drivers. There were, at least at one point, supposed to be ways to get it working anyway...but not at stock.

[Deadgye]

I googled the datasheet, in the "Dual graphics card setup" section it says

Install only identical SLI-ready graphics cards that are ASUS and NVIDIA certified. Different types of graphics cards will not work together properly.

Looks like the motherboard is only designed to run one card at 16x or two identical cards at 8x/8x specifically for SLI/Cross.

[Arkanna]

I remember those weird SLI keys. I saw you tried it both with the key removed and with the key in the SLI position, but did you try running your setup with the key left in the default, non-SLI position? I have a feeling you may need a different motherboard for what you're trying to do.

[xerodok]

I've made this same post on Reddit, a few people have recommended I try using a 'dummy plug' for the secondary GPU. I took a few resistors and made a VGA/DVI converter into a dummy plug to try when I get home.

[Arkanna]

If it ends up you need another board, let me know. I have a microATX Z87 board I'd part with for pretty cheap, it just needs a CMOS battery.

[xerodok]

If it ends up you need another board, let me know. I have a microATX Z87 board I'd part with for pretty cheap, it just needs a CMOS battery.

Noted, thanks!