Crossfire board, single GFX card

[Firestrider]

I have a 790GX crossfire motherboard that has a Master PCI-E slot and Slave PCI-E slot that is written on the board. I think the board has a maximum of 16x PCI-E 2.0 lanes.

I was wondering if I could put my graphics card in the Slave PCI-E slot and have it run at PCI-E 2.0 x16. The reason why I want it in the Slave slot is because it is higher on the motherboard and therefore more room below it for the fan and heat.

Right now I have it in the Master slot at PCI-E 2.0 x8, but when it put it in the Slave slot to goes to PCI-E 1.0 x8.

[Nebulous]

Is there an option in the bios to enable/disable the PCIE slots?

[Automiketic]

u will prolly have to keep it in the top slot to obtain maximum frequency. although i dont have expereince with that particular board. as neb said check your bios for some sort of setting. good luck.

[Firestrider]

The slave slot is on the top and the master is on the bottom (kinda weird IMO). The slave slot should work at PCI-E 2.0 x8 and the master slot should work at PCI-E 2.0 x16 (single card) or x8 (in crossfire). To get PCI-E 2.0 x16 in the master slot you have to use the PCI-E paddle card that came with the motherboard in the slave slot.

The reason I want to put my graphics card in the slave slot is because I have a PCI sound card that won't fit if I put the GFX card in the master slot.

I tried enabling PCI-E Gen2 compliance mode and support to enabled and auto in BIOS and still am getting PCI-E x16 1.0 @ 8x in GPU-Z. There was an option for ASPM and L0/L1 but I have no idea what that is.

[Firestrider]

Do you think PCI-E 1.0 x8 is bottlenecking the card?

[Cuiiey]

Isn't PCI-E x8 practically as fast as x16 anyways??? isn't this why intel have these with their p45 chipsets?

[BossBorot]

pci-e 8x is good enough for a single gpu system even on pci-e 1.0a. You only really want pci-e 16x 1.0a or pci-e 8x+ 2.0 if you are running dual gpu solutions that need more bandwidth for communication between the GPUs.

a 4850 should work fine at pci-e 1.0a 8x by itself. However to be sure run whatever game you play most's included benchmark with the card in each position to justify the move from master to slave

Isn't PCI-E x8 practically as fast as x16 anyways??? isn't this why intel have these with their p45 chipsets?

yes and no.

on the p45 you can be limited to 8x however the p45 chipset is natively 2.0. This effectively means that 8x on a p45 (gen 2.0 with compatable cards) is eqivalent to 16x on a 1.0a chipset like the p35 or earlier chipsets.

I dont want to get to much into the p35 but it isnt limited by 1.0a. It is limited by the pci-e lanes provided by the northbridge which limits it to 4x (1.0a) on the slave slot in crossfire situations.

[Firestrider]

I'm not sure if 3DM06 will give me an accurate measurement on real game performance with the PCI-E bus, but I got a 12K score which seems about right for my system.