how many pci "lanes" necessary to crunch?

[bmwr606]

can a GPU run in this slot?

1 x PCIe 2.0 x16 (max. at x4 mode, compatible with PCIe x1 and x4 devices)

i see lots of 1155 CPU boards have this kind of PCI 2 slot

[Maxwell]

Yes. Assuming you're just crunching, you need very little bandwidth for the slot.

[JPMexplanationinmoretechnicallanguage]...

[Dandasarge]

Yes. Assuming you're just crunching, you need very little bandwidth for the slot.

[JPMexplanationinmoretechnicallanguage]...

If JPM don't I will, my answer is only theory but I think the "Dan" did this.

[Fire$torm]

IIRC JPM has done this too. On the old forum he posted a detailed How-To on modding a PCIe 1x slot for a 4x card. Or something like that. Damn... we need those archives!!!

[John P. Myers]

Yeah, if you're only crunching, any bandwidth rating on any slot is enough. PCI slots only have 133MB/sec bandwidth, and for all of us that have a 9500GT we know this works just fine. In most cases, you're only working with a 7kB to 20kB data file in the first place. It's quite effortless to send a 20kB data file through a 133MB/sec conection. You could send 6,650 of those files every single second, but since it takes more than 1 second to crunch any given WU, you'll never hit this cap.

As for a PCIe x1, that's 500MB/sec. And since 133MB/sec is more than enough, no reason to argue this point.

However, if you do gaming on the side, it's best not to go below PCIe x8. 2 5970's in Xfire with an x8 connection only lose 1% to 2% performance as compared to them both having an x16 connection. 8% drop at x4. 2 5970's in x8 slots still have an 8GB/sec throughput.

1 frame at 1080p HD resolution is only 7.91MB so 60 frames per second requires 474.6MB (935.5MB @ 2560x1600) of your bandwidth (note this is output usage from the GPU only. Input data accounts for another chunk of your throughput).

So for crunching any slot will do. For gaming, stick to at least an x8 unless you're getting 150+ FPS. Then an x4 won't hurt anything.