Dual vs Single graphic card question.

[Imouto]

For example a HD 5850 CF is pretty close to a GTX 580 performance wise. I've been wondering about these setups for a while.

Is there any PCIe bandwidth usage difference between GTX 580 and HD 5850 CF?
Is there any CPU usage difference between GTX 580 and HD 5850 CF?

Are these reviews biased in any way?

http://www.techpowerup.com/reviews/NVIDIA/GTX_480_PCI-Express_Scaling/24.html
http://www.hardocp.com/article/2010/08/25/gtx_480_sli_pcie_bandwidth_perf_x16x16_vs_x4x4/1

Thanks.

 

[TakeNoPrisoners]

Crossfire and SLI do add a bit of CPU overhead. No they are not biased. It depends on your motherboard if the bandwith matters. But with two 5850's it doesn't unless your running 4x or 1x each.

 

[Imouto]

So a GTX 580 should deliver the same performance as a HD 5850 CF if they're mounted in the same machine?

Why would anyone concerned about money buy a GTX 580 then? In my country you can get 2 brand new Sapphire HD 5850 Xtreme for 240€ and the cheapest 580 is over 400€.

 

[JamesV]

So a GTX 580 should deliver the same performance as a HD 5850 CF if they're mounted in the same machine?

Yes, if those cards performed the same, trying each one out individually on the same PC should give the same results. The only thing that can't be duplicated perfectly are the drivers, so you may actually see some differences.

Why would anyone concerned about money buy a GTX 580 then? In my country you can get 2 brand new Sapphire HD 5850 Xtreme for 240€ and the cheapest 580 is over 400€.

Nvidia has for the most part been the stronger offering. I didn't read your review links, but I've never seen an ATI/AMD card and an Nvidia card perform exactly the same. Sure they sometimes get the same FPS in a game, but never in all games or all applications.

Brand loyalty is also another reason. When you use a brand for a long time, and see a competitor for $50 less, you tend to think that $50 is well spent on the brand you know will work well.

 

[cusideabelincoln]

So a GTX 580 should deliver the same performance as a HD 5850 CF if they're mounted in the same machine?

Why would anyone concerned about money buy a GTX 580 then? In my country you can get 2 brand new Sapphire HD 5850 Xtreme for 240€ and the cheapest 580 is over 400€.

The 5850 is an older model; they are at a cheap price to sell them. The GTX 580 is Nvidia's flagship. Flagship GPUs, especially Nvidia's, typically carry a price premium. And a third reason is dual video cards require more driver support than single video cards. If you don't have driver support for a game then only a single card is going to be able to do work in a dual card setup. Sometimes dual cards just don't scale very well so two 5850s would end up slower than a 580, but still faster than a single 5850.