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Graphic card Fitting Queastion and more

Last response: in Graphics & Displays
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September 19, 2008 9:41:09 PM

Can a ati 4870 x2 fit in a thermaltake lanbox and would a PCIe x16 1.0 limit that card because i heard that thecards out today don't use the full bandwidth of the 2.0 slot .
thx in advance for the advice
September 19, 2008 10:06:10 PM

I'm not sure if it'll fit, but a PCIe 1.0 interface definatly will bottleneck that card.
September 19, 2008 10:31:58 PM

pci-e 2.0 is backward compatible with pci-e 1,the main difference between the 2 protocols is voltage supplied to the card by the mobo 2.0 is much higher,as to the rest ,,i think that only time will tell...:) 
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September 19, 2008 11:00:27 PM

Bandwidth on 2.0 is also double that of 1.0, and that's where this card will be limited.
September 20, 2008 4:19:23 PM

What kind of system are you planning on and what resolution are you going to game at? I ask because you may want to reconsider buying an x2 since it sounds like it could be way too much for your system to utilize. If your rig isn't using PCIe 2.0 slots then I would assume that you aren't running a high end system and a single GPU, either 260 or a 4870, sounds like it would be the smarter option on a performance / dollar aspect.

But...good question though.

A 1.1 PCIe x16 slot has the bandwidth of 4GB/s (.25 GB/s per lane)(16 lanes)
A 2.0 PCIe x8 slot has the same 4GB/s bandwidth (.50 GB/s per lane)(8 lanes)
A 2.0 PCIe x16 slot comes in at 8GB/s (you can do the math now)

So running in your 1.1 x16 slot will be just like running in a 2.0 x8 slot minus the extra 75W of power surging through the slot to the video card. This is relevant because it isn't possible to do an accurate PCIe 1.0 to 2.0 VGA comparison since the chipsets would have to be different and they matter in overall system performance.

I am going to leave you with not much of an answer but maybe some more help for you to find one. As far as I know, there isn't a review of the 4870x2 that compares PCIe 2.0 x16 vs PCIe 2.0 x8 to see if the bandwidth makes a difference. The PCIe bridge between the two GPUs in the R700 allows them to communicate at 5GB/s FYI. We are talking some huge bandwidths on that monster.

I can for sure say that you will encounter a choke at higher resolutions and at lower resolutions, you shouldn't be bothering with an x2 anyway. I think it is a smart buy to get an x2 over a 4870 xfire setup if you go to x8 mode because then you have to fight with lower bandwidth for xfire where as the x2 does xfire right on the VGA. For you though, consider how powerful your rig is and if the x2 would even do well if you had a PCIe 2.0 x16 slot to put it in.



Here is an interesting article by Toms but it doesn't cover the R700 so you can't really make any direct conclusions. However, you can see that at higher resolutions, the extra bandwidth does make a difference. I would assume it to be magnified with the monster R700 too.
http://www.tomshardware.com/reviews/pci-express-2-0,191...

Also, tweaktown has a x8/x8 vs x16/x16 xfire comparison here for viewing pleasure but again, not directly comparable to the x2 but you can get an idea of how the bandwidth affects GPUs.
http://www.tweaktown.com/articles/1472/intel_p45_vs_x48...
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