PCIe 2.0 X16 vs. X4

[jaylim0512]

I have this mother board:

It has one PCIe 2.0 X 16 and one X4 slot.

If I were to buy a HD 5830 and crossfire them would I see a significant drop in performance compared to two X16 slots?

I read this page, but how credible is this information because they just taped off the pins to make it a X4 slot?

http://www.hardocp.com/article/2010/08/25/gtx_480_sli_pcie_bandwidth_perf_x16x16_vs_x4x4

How many FPS do you think I'll get in crysis?

Last question is HD 5850 or HD 5830 CrossFire? (Considering price and performance)

 

[notty22]

Toms Hardware just did a 3 part series on crossfire/sli, dealing with different aspects.
Part 1, The Cards: Triple-GPU Scaling: AMD CrossFire Vs. Nvidia SLI
Part 2, The Slots: GeForce And Radeon On Intel's P67: PCIe Scaling Explored
Part 3, The Chipsets: P67, X58, And NF200: The Best Platform For CrossFire And SLI

#2, they take a look at a gtx 570 and a 6950 , single card, performance in the various pci-x slots 4x 8x 16x.

Surprising results, some games show very little fps difference. Except there is one game F1, that shows pretty drastic differences.
This test is particularly pertinent to the recent crossfire/sli testing review done at Hocp, I will have to post this there to.


http://www.tomshardware.com/reviews/pci-express-scaling-p67-chipset-gaming-performance,2887-5.html

I would imagine, less than ideal results, especially in F1, with one card in x4 and the other in x16, but games like Crysis, would probably perform more like 8x-8x. I

 

[SickBeast]

I'm running GTX 460 SLI on a 16x/4x setup and it's great. My cards consistently benchmark faster than a GTX 580, which is in line with what I've read in reviews.

I think you'll lose 3% or so in some cases, but the majority of the time there will be hardly any difference (1%).

By the way, the difference seems more pronounced at lower resolutions for some reason. HardOCP tested at 2560x1600 and there was essentially no difference at all. Tom's Hardware tested at 1080P and the performance delta was greater.

Perhaps someone on here can explain to us why this is happening.

 

[RussianSensation]

If you have a P55 style motherboard which has half the lane bandwidth off the P55 chipset, the PCIe 4x will become a bigger issue. If you have the newer P67 chipset motherboard, PCIe 4x is less of an non-issue.

See this thread for more details.

How many FPS do you think I'll get in crysis?

5830 CF setup is not much faster than a single HD5870. See this review for reference. Personally, if I was in your shoes, I'd probably sell your current 5830 and get an HD6950 2GB/GTX560 Ti. Or if you are looking to buy 2x 5830s, an overclocked 6950 or a GTX560 should easily match it without any of the drawbacks of additional noise and power consumption and possibly poor scaling down the line.

As far as HD5850 CF is concerned, that also isn't a good option. If you are going CF, consider HD6850s. Much better CF scaling than HD5850s. Performance wise, HD6850s in CF is at least as fast as a single GTX580, for half the price.