How many PCIe lanes nessecary for GPU if I want to mine?

[nodemaster]

Hi all,

I'm a Systems Architect and an occasional gamer but for some strange reason I never was too interested in GPUs in general as I was more focused on server hardware. I hope someone can verify or correct my assumptions. I'm using a GeForce 9800 GTX in an PCIe x16 Slot. Now I'm thinking about buying a second GPU for constant mining. My Motherboard has a second PCIe Slot. It's form factor is x12 but it only uses four lanes. I understand this is a bad thing for gaming, as the bandwidth is too small to transfer huge amounts of textures and stuff into the graphics card RAM. But for mining we only use the GPU cycles in order to number crunch numbers, right? We are not moving tons of bits to or from the graphics card? Is my assumption correct, that the amount of lanes does not matter as long as a x16 card fits into the slot?

Furthermore is it nessecary to buy a second GPU of the same make or can I choose to buy any other GPU even one with ATI chip? If so, do you have recommendations what gives the best Mhash/$ ratio?

Thank you in advance

[dust]

You are correct, PCIe bandwidth is not important for mining.  x1 will work.

Using both nvidia and ATI cards in one computer might be possible, but is probably a huge hassle in terms of drivers.  Using different GPUs from the either nvidia or ATI works fine.

If you are buying a new card for mining, just ditch the 9800 and get AMD/ATI.  5970s and 6990s are the best cards for mining long-term.  A cheap 5870 (<=$200) is also pretty good value.

https://en.bitcoin.it/wiki/Mining_hardware_comparison

[nodemaster]

Thank you very much for the hardware comparison link. I always thought my 9800 GTX is a quiet decent GPU  Seems I was mistaken. I think I go for two ATI card and hope to get a good offer on ebay for the 9800 

[FooDSt4mP]

Thank you very much for the hardware comparison link. I always thought my 9800 GTX is a quiet decent GPU  Seems I was mistaken. I think I go for two ATI card and hope to get a good offer on ebay for the 9800 

It is decent... but ATI's stream processors (in 16k or 32k quantities ) are ideal for bitcoin mining.