Which P67 mobos allow x8/x8 SLI/Xfire

N

nalc

[H]ard|Gawd
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Seems like just about every P67 mobo has two or three PCIE x16 connectors, but as we all know, they are limited to 20 PCIe lanes.

I was wondering if we could get a list going of which mobos allow x8/x8 crossfire/sli, and which ones only allow x16/x4. I've been reading reviews, and many of them don't bother mentioning it. They'll just say "Supports Crossfire! Two PCI Express x16 slots!" without specifying the difference. I'll update this list as I read more reviews.

Asus:
P8P67-M Pro x8/x8 sli/xfire
P8P67 LE - x16/x4
P8P67 - x16/x4 xfire
P8P67 Pro - x8/x8 sli/xfire
P8P67 Evo
P8P67 Deluxe - x8/x8 sli/xfire
P8P67 WS Revolution - 16x/8x/8x trisli/trifire (NF200)
Sabertooth TUF - x8/x8 sli/xfire
Maximus

Gigabyte:
P67A-UD3 - x16/x4 xfire
P67A-UD3R - x16/x4 xfire
P67A-UD4 - x8/x8 sli/xfire
P67A-UD5 - x8/x8 sli/xfire
P67A-UD7 - x16/x16/x8 trisli/trifire (NF200)

Intel:
DP67BG-P67 - x8/x8 sli/xfire

MSI:
P67-GD55
P67-GD65 - x8/x8 sli/xfire
 
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The P8P67 WS Revolution supports 16x8 Crossfire / SLI and 16x8x8 CrossfireX / SLI. The Gigabyte P67A-UD7 also supports 2 and 3-Way SLI as well as Crossfire/CrossfireX. It has less slots than the P8P67 WS Revolution though. It should do 16x8x8.
 
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Well, isn't 16x 4x crossfire something less than 3% performance hit? It doesn't seem to be a big deal. The better boards offer better features, I would use those to make a purchasing decision, not the pcie lanes.
 
SonicTron said:
Well, isn't 16x 4x crossfire something less than 3% performance hit? It doesn't seem to be a big deal. The better boards offer better features, I would use those to make a purchasing decision, not the pcie lanes.
Click to expand...

I think it's x8/x8 that has less than a 3% performance hit versus x16/x16. x16/x4 is pretty bad, afaik. Plus, it seems like none of the x16/x4 boards are SLI capable. Does SLI require two equal lanes?
 
Damn, I was going to go 2600k with 3x GTX 580's but no motherboards support 3x 16X lanes. The only board that comes close is the P67A-UD7 - x16/x16/x8 trisli/trifire (NF200) but I am sure the last 8x slot would definitely slow down an overclocked GTX 580 quite a bit. It was shown that the GTX 480 even was starting to get noticeably limited using Surround with a 8x PCI-e lane here on [H] and OC'd 580 is going to push some 30% more bandwidth.
 
nalc said:
I think it's x8/x8 that has less than a 3% performance hit versus x16/x16. x16/x4 is pretty bad, afaik. Plus, it seems like none of the x16/x4 boards are SLI capable. Does SLI require two equal lanes?
Click to expand...

Nope, SLI does not.
 
Vega said:
Damn, I was going to go 2600k with 3x GTX 580's but no motherboards support 3x 16X lanes. The only board that comes close is the P67A-UD7 - x16/x16/x8 trisli/trifire (NF200) but I am sure the last 8x slot would definitely slow down an overclocked GTX 580 quite a bit. It was shown that the GTX 480 even was starting to get noticeably limited using Surround with a 8x PCI-e lane here on [H] and OC'd 580 is going to push some 30% more bandwidth.
Click to expand...

only for triple sli. not dual.
 
nalc said:
I think it's x8/x8 that has less than a 3% performance hit versus x16/x16. x16/x4 is pretty bad, afaik. Plus, it seems like none of the x16/x4 boards are SLI capable. Does SLI require two equal lanes?
Click to expand...

As far as I know Nvidia does not certify boards with x16/x4 for SLI because of the performance hit.


Vega said:
Damn, I was going to go 2600k with 3x GTX 580's but no motherboards support 3x 16X lanes. The only board that comes close is the P67A-UD7 - x16/x16/x8 trisli/trifire (NF200) but I am sure the last 8x slot would definitely slow down an overclocked GTX 580 quite a bit. It was shown that the GTX 480 even was starting to get noticeably limited using Surround with a 8x PCI-e lane here on [H] and OC'd 580 is going to push some 30% more bandwidth.
Click to expand...

How can x16/x16/x8 even be implemented? If it uses NF200 the best possible would be x16/x8/x8. In any case for every P67 board all of the data has to be squeezed through ONE x16 processor interface. It's not like NF200 can magically create bandwidth. It's main benefit is that if the first card needs more bandwidth than the other two (read: more than a x8 interface can support) the NF200 can distribute that accordingly. But if x8 is not enough for a single oc'd GTX580, then the upstream x16 will also not be enough for three oc'd GTX580. The only way to get three or more full x16 ports is to use a dual processor LGA1366 board with two of the X58 equivalent server chipsets like Supermicro sells.

EDIT: I did take a look at the manual of the P67A-UD7. It does support x16/x8/x8, not x16/x16/x8.
 
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OK; so my question is this: Would a 6990 and a 6950 on an x16/x8 board give higher performance than three 6590s (unlocked) on the Gigabyte UD7? I'm looking to go trifire with my 2500k and the UD7 was the frontrunner for my available options.
 
There are no x16/x8 P67 boards. The only way you can achieve such a configuration is to use a board with a NF200 like the UD7 and populate the first and the last slot. However this is not optimal, because you halve the available bandwidth and leave the other 8 lanes from the second x16 port unused. In fact that is the configuration I used prior to my upgrade to a P67 board. I had the P55A-UD7 before, which has the same slot configuration as the P67A-UD7. While it is not the optimal configuration performance-wise, it gives the upper card two more slots of breathing room.

I would recommend the ASUS WS Revolution board, as it has a better slot layout for two-card SLI. On the other hand I expect that you will see even less difference between x16/x8 and x16/x16 if the x16 slot is populated with a dual-GPU card. Keep in mind that the processor interface is only x16, so each GPU has effectively 5.3 lanes for upstream transfers for Tri-SLI. Of course, there may be inter-GPU communication, which will profit from the maximum number of lanes per card.
 
Well I said F-it and ordered my third 6950 and the Gigabyte UD7 last night.... I'll report back with performance but I finally stabilized my 2500k at 4.8 on my MSI board last night. If I can maintain 4.8 or better on the UD7 and have three cards running strong I'll be a happy camper.
 
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