SLI mobos (2 x 16x pci-e) but Xfire mobos (2x 8x pci-e)???

[vpsaline]

Only SLI mobos such as the 680i can run two cards @16x each? The Xfire mobos which Ive looked at such as the RD600 and P5W-DH Deluxe seem to only function 2 x 8x. Whats the deal? With the upcoming X2800 XTX 1024 its tempting to switch over to a crossfire board but will the dual 8x hurt it's xfire performance or lifespan of the mobo?

 

[harmattan]

Sad, in't it? And I had pci-e 16x back on my old Abit AN8 last year. What gives?

I'd bet performance won't suffer a lot for X-fire in the short term on Dx9, but 8x will definitely be a limiter in Dx10, particularly for X2800.

I'd steer clear of X-fire and just go with one X2800 since bandwidth is 16x in single-card configuration. That is, if R600 is ever released...

 

[rammedstein]

the bandwidth from pci-e 8x is sufficient for crossfire, or sli, there is only a negligible impact between 8x and 16x, about 5-10%. crossfire is only 8x because they don't see the point of wasting money on the chip when the performance difference littleand the price is quite large, hence the difference between the 965 and the 975x, the price difference is about $100 for an extra 5-10% on the pci-e but limits the overclocking of the cpu slightly

 

[Slobogob]

the bandwidth from pci-e 8x is sufficient for crossfire, or sli, there is only a negligible impact between 8x and 16x, about 5-10%. crossfire is only 8x because they don't see the point of wasting money on the chip when the performance difference littleand the price is quite large, hence the difference between the 965 and the 975x, the price difference is about $100 for an extra 5-10% on the pci-e but limits the overclocking of the cpu slightly

8O

If the impact was 5-10% then they would care. Your argument is pointless. SLI and Crossfire cater to the enthusiast crowd which cares a lot about performance and thus they would use real 16x lane slots. As it seems AMD seems to be sure that 8x is more than enough to run all it´s current and coming offerings at peak performance. Tests made by THG and some other hardware sites have shown that for most of the DX9 cards 4x is more than enough.
I´d like you to clarify your statements regarding your comparison of intels 965 and 975 chipsets in crossfire or sli performance since i´m not quite sure what you are trying to say. :?:

 

[vpsaline]

Thanks for the input guys, keep it coming, I appreciate everyone's comments.

I was able to finaly find an ATI board that supports 2x 16x (when xfired).
DFI LANParty UT CFX3200-DR RD580 Crossfire
http://www.ncix.com/products/index.php?sku=17922&vpn=LP%20UT%20CFX3200-DR&manufacture=DFI

Expansion Slots 2 PCI Express#16 slots
For Cross-Fire mode, both slots operate as x16
2 PCI Express#1 slot
3 x PCIs

Now I guess this raises a new question if I may. Any word on an upcoming or existing intel mobo that supports xfire with the same degree of future upgradability as the 680is (quad-core, 1333fsb, 1200mhz ddr2, 2x 16x pci-e xfire-mode)???

 

[rammedstein]

i was saying the different in over clocking performance from the 975 is less than the 965. and no, it wouldn't because if there is an overall performance loss of 5-10% because there is not enough bandwidth on one card wouldn't effect as much with crossfire because they split the load evenly, resulting in less bandwidth to each card required but an overall bandwidth increase.