PCI-E 2.0 and 1.1 question

[Static EMP]

I've searched through lots of forums, but could not find the answer to this. So forgive me for another 2.0 vs. 1.1, question, but after lots of due diligence, I think it's safe to ask this question.

Everybody knows that PCI-E 2.0 is not worth it yet, because no video cards are capable of saturating the bandwidth yet. My question is, how do you know how much bandwidth a video card will saturate? Is there a certain spec on the video card which signifies how much bandwidth the card is capable of saturating? I just got a 9800 GX2, which has 128 MB of memory bandwidth, and even pci-e 2.0 only has 8 mb of bandwidth. From what I've read, the card's memory bandwidth is internal and doesn't traverse the PCI-E bus.

I want to know this for a couple of reasons:

1. I want to be able to know when graphics cards are using PCI-E 2.0 to it's full benefit.
2. From what I've read, the 9800 GX2 doesn't improve with PCI-E 2.0 However, it might be worth it to pay the difference an return my ASUS P5K-E P35 motherboard and get an nforce 790i which is compatible with pci-e 2.0.

Any explanation would be appreciated. Thanks!

 

[Lithan]

Probably could get a rough estimate by comparing performance in 8x2 sli to 16x2 sli on boards that perform similarly with a single cards.

 

[Auric]

Everybody knows PCIe 1.x was not necessary versus AGP, unlike the transition from PCI. But if planning on running a mainboard for several years and upgrading along the way then given both options the current standard (PCIe 2.0) is obviously preferred. Otherwise it matters less than reliability and other features.

CPU-wise, both are approaching the end of the line so the GPU bus may be as irrelevant as with last major platform transition except in the case of hard-core gamers who want to maintain the latest 'n' greatest including multiple cards.

 

[Static EMP]

I see. But when people say that today's graphics cards don't saturate the bandwidth of PCI-E 2.0, or even 1.1, where does this information come from? Can you look at a graphics card's specs and be able to estimate how much bandwidth it will saturate? If so, what spec or specs determine this?

 

[superunknown98]

I have never seen this claim quatified, however the best way to test this is by benchmarking at different link speeds. If for instance at 16 lanes you get 100 FPS and you get the same 100 FPS at 8 lanes, then you know the bandwidth is not saturated.

 

[themisfit610]

Not really... It's hard to say.

Don't worry about it, most cards are still perfectly fine with 8x PCIe 1.1. By the time you are thinking about getting a card that is bottlenecked even slightly by PCIe 1.1 - you will be ready to spend $100 on a new motherboard lol

~Misfit

 

[Throckmorton]

What exactly is all that bandwidth used for in the first place?