PCI-E pipeline information

[Colonel_Panic]

I'm planning my second computer build and want to cover all the bases, including SLI should I be so inclined. I'll be using 1 GTX275-285 to start, and maybe add a second one in a few years. The motherboards I've been reading about have 2 PCI-E x16 slots, but most say its either 1 at 16x or 2 at 8x. Do I need to find a mobo with 2 at 16x or would 8x work for something like these cards? What are the impacts of running a graphics card in a slot lower than the specs?

 

[SicKlown42012]

PCI-E 2.0 8X isn't much, if any, of a bottleneck. In short, the motherboards you're looking at should be fine.

 

[trick0502]

if you dont have 2 275-85's now, in a few years they will be really hard to find. they went eol in nov.

 

[defaultluser]

What are the impacts of running a graphics card in a slot lower than the specs?

For a single card, on PCIe 2.0: virtually no performance hit until you get below 4x

For SLI / CrossFireX 2 cards:

8x - virtually no hit
4x - small performance hit.
2x - major performance hit.
1x - don't even bother.

P55 motherboards with 8x8 configurations are the best to go for, as there is only a %5 performance hit versus 16x16 on X58.

The problem with the 16x4 P55 motherboards is this: although you give plenty of bandwidth to the 16x PCIe 2.0 slot, those 4x PCIe channels are version 1.1, so they run at the same speed as a PCIe 2.0 2x slot. If you look at my rundown above, you can see that 2x brings a major performance hit.

So, just make sure you get an 8x8 P55 motherboard. You should be fine.

 

[Colonel_Panic]

Thanks for all the replies.

if you dont have 2 275-85's now, in a few years they will be really hard to find. they went eol in nov.

Probably true, I was just using them as a reference. I'll probably end up going with whatever is at the current 285 price point.

 

[ShuttleLuv]

X8 with single card ? maybe 1% difference if that

X8 with crossfire ? maybe 3-5% if that but still barely noticeable (like 2-3 fps tops)

 

[cyclone3d]

Thanks for all the replies.



Probably true, I was just using them as a reference. I'll probably end up going with whatever is at the current 285 price point.

And by that time.... 8x will most likely be a pretty decent bottleneck.