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Tri-crossfire bandwidth question

W

Wag

[H]ard|Gawd
Joined
Aug 29, 2006
Messages
1,584
OK, got my tri-crossfire 6950 setup going in my Asrock P67 Extreme4 mobo and the catalyst ctrl panel says:

3 GPUs (8 4 0)

My motherboard manual says:

In 3-Way CrossFireXTM mode, please install PCI Express x16
graphics cards on PCIE2, PCIE4 and PCIE5 slots. Therefore, PCIE2
and PCIE4 slots will work at x8 bandwidth while PCIE5 slot will work
at x4 bandwidth.
Click to expand...

Shouldn't that mean the bandwidth should be:

8, 8, 4? Do I have that wrong?

Is 8, 4, 0 correct?
 
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I have three 6950s in an Asus Maximus IV Extreme and CCC shows 3 GPUs (0 6 4).... I don't think that is supposed to be referencing bandwidth cause performance is definitely on par with all three cards running full speed.
 
Thx. Definitely working with 3 cards, although I wish I had more bandwidth- but the motherboards with 16x/16x support cost in the $300 range. I didn't do enough research. Oh well, it's definitely working though, I get about a 3000pt boost in 3DMark11 with the 3rd GPU active.
 
Those numbers that are shown aren't talking about bandwidth, it's not even accurate. With my Quad GPU config it shows "3 GPUs (12 0 10)" when all 4 GPUs are indeed working and both cards are in 8x slots.

You don't need to worry about bandwidth much, even on a 4x slot, assuming you have a PCIE 2.0 motherboard.
 
Yeah, if you google the bandwidth concerns you'll see that even without all cards running at x16, the performance hit is virtually non-existent. That was a concern of mine before I picked up my board (M4E), but it actually outperformed the X58 setup in testing. Too bad it still cost me over $300 :rolleyes:..... can't complain though cause the system FLIES.
 
The noteworthy problem with Tri-Crossfire bandwidth appears when you run a resolution greater than 1080p x 3. As user Vega discovered on here, AMD's bridge and CF implementation kills performance if you are trying to roll with Tri-Fire *and* 1600p x 3.

But that has nothing to do with PCI-e lane bandwidth.
 
I'm beginning to think I should have invested a bit more in a motherboard with more 16x PCI-E slots. Oh well, I still break 13000 in 3DMark11 which is about average for my setup comparing to other similar setups.

I intend on adding some more displays in the future so at least I'm good to go- and 3 unlocked 6950s were too good a deal to pass up.
 
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