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Pcie 2.0 in a 1.1 slot - how bad of a performance hit?

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I am currently using a DFI Lanparty DK P35. Being that it is a P35 motherboard, it does not have a pci-express 2.0 slot. My video card is quite aged (ATI X850 XT) and I was planning on picking up a new one. My question is, if I were to slap an HD3870 X2 in my system, how much worse would it perform than if it were in a 2.0 slot? I am wondering if maybe I should switch to a different motherboard that supports pci-express 2.0 (the MSI P7N 750i looks pretty nice).

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I was reading an article at Tweaktown on the 3870x2 vs 2x3870 Crossfire and in the conclusion it briefly mentioned that "initial results show some decent gains for the X2 when moving to a PCI-E 2.0 motherboard." They didn't state by how much though, and by decent, what do they mean? I would guess 5%-10% gain in FPS.

See this one:
http://www.tomshardware.com/2008/01/23/crossfire_meets_...


Conclusion - Switching To PCI Express 2.0 Yields No Improvement
Quote:
"For now, the move from PCI Express 1.0a to 2.0 does not result in a performance increase with the current crop of graphics cards. Despite the fact that it doesn't feature the PCIe 2.0 interface, ATI's Radeon HD2900 XT gains two percent more performance, as do the HD3850 and HD3870, as well as Nvidia's Geforce 8800 GT. Such a small improvement could have many causes completely unrelated to the new interface, such as the newer chipset, slightly higher system memory frequency, or simply margin of error"

lashrimp said:
See this one:
http://www.tomshardware.com/2008/01/23/crossfire_meets_...


Conclusion - Switching To PCI Express 2.0 Yields No Improvement
Quote:
"For now, the move from PCI Express 1.0a to 2.0 does not result in a performance increase with the current crop of graphics cards. Despite the fact that it doesn't feature the PCIe 2.0 interface, ATI's Radeon HD2900 XT gains two percent more performance, as do the HD3850 and HD3870, as well as Nvidia's Geforce 8800 GT. Such a small improvement could have many causes completely unrelated to the new interface, such as the newer chipset, slightly higher system memory frequency, or simply margin of error"

It does not say anything about the HD3870x2 does it? And the OP was asking about the HD3870x2.

Quote:
Our switch to the X38 chipset for Crossfire tests was overdue. The dual x16 connections improve performance by 6 to 7.7 percent on average, while optimized games such as Call of Duty 4 run nearly 20 percent faster. Looking only at games and resolutions that show a tangible performance boost, we saw an improvement of 12 to 15 percent, on average.


Assuming that a 3870x2 performs like a 2 x 3870, there should be a performance boost. As I said before, Tweaktown has stated that moving the 3870x2 to PCIe2.0 has yielded "decent" gains, although it didn't state how much more. I believe that moving to PCIe2.0, the 3870x2 should see somewhere between 5%-10% more FPS.
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Good to know! I have been hunting for an article like that for a little while now, I even searched Tom's Hardware (guess I didn't know where to look). But I guess it doesn't shed too much light on the x2 situation. Basically what I am really looking for here is a graphics card that will last a good while (two years might be pushing it?) which is what made me look in the x2's direction.

skittle said:
Considering the 8800gts 512 gained <2% when goind from PCIe 1.0a to 2.0... Im skeptical that tweaktown found "decent improvements" in excess of 5%

That's what I thought too. But then I thought what if the 3870x2 is more compatible with PCIe 2.0? I want to see a review that compares PCIe 1.1 and PCIe 2.0 before confidently saying that PCIe 2.0 will show a performance boost.

In regards to this old post, I was wondering if anything has changed with the newest gen of cards. I'm looking at the 4870 and the GTX 260 216 Core. Would slapping one of these cards into an older PCIe 1.x slot put a damper on real performance?

I essentially want to replace an 8800 GTS 640MB with one of these cards, but wasn't really looking to get a new motherboard unless the PCIe 2.0 will make a huge (15-20%) difference.

Thoughts?
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