? re: Triple CrossfireX

[magoo]

I have been using three HD 6970s in Crossfire.
They cant breathe well. They work fine but are really packed in tight.
I just got a 6990.
I have a Rampage III Formula with 16x-16x or 16x-8x-8x. So a two card setup will get dual 16x lanes.

I am wondering if ther is ANY advantage to where the 6990 is placed, in other words does it really matter if it is the master card (top) or the slave?

I cant think of a reason why it would matter, and the 6990 would get more fresh air on the bottom orientation in my case.

Opinions??

 

[sabregen]

you'll get no appreciable difference between an x8 and x16 PCI-E 2.0 or higher slot, if the GPU is single die. however, since the 6990 is dual die, I'd give it all the bandwidth you can. put it in a true x16.

 

[sirmonkey1985]

the lane speeds don't matter between 16x and 8x neither the 6970 nor the 6990 will saturate them.

where the problem lies is depending on what card you want to be the card the displays are connected to and if your motherboard allows you to select that pci-e slot to be the primary display slot. personally i'd use the 6990 as the primary display card and use the 6970 as the secondary. either way all 3 gpu's will be locked to the 6990 clocks.

also because your motherboard has 3 pci-e slots you can set the 6990 to the top, leave the second slot empty and put the 6970 on the 3rd slot but you will need a longer crossfire bridge but it will leave both cards getting fresh air.

 

[Elmy]

They would breathe just fine if you watercooled them ..

 

[XacTactX]

In Eyefinity, there is a 5-10% performance loss going from 16x to 8x with GTX 480s. The 6990 usses a PLX bridge to split your original 16x slot into an 8x, or an 8x into a 4x, so I suggest you use a 16x slot if possible.

http://www.hardocp.com/article/2010/08/23/gtx_480_sli_pcie_bandwidth_perf_x16x16_vs_x8x8/2

 

[shantd]

Sounds pretty unanimous re: going with the primary.

Since it sounds like you can afford it, why not water cool like the above guy says? I've heard those 6990s can get hot...especially if you're gonna have a 6970 right below it.

 

[magoo]

Appreciate the comments.
I'm not concerned about the PCI-e lanes.
I'm just concerned about the primary vs secondary configuration.

I am wondering if there will be any display differences between the 6990 being master and vice-versa.

I have waterblocks for both cards, BTW.....I waited to get the blocks until I had the 6990 in my hot-little-hands.

I think it will be 6990 primary and 6970 secondary.

I clicked the BIOS on the 6990 to position #1, these things overclock like bandits......I just hope the single card can keep up!!

Thanks again for the help....it was as I suspected, but I wanted to hear it before i did it.

 

[Michael Turbo]

In Eyefinity, there is a 5-10% performance loss going from 16x to 8x with GTX 480s. The 6990 usses a PLX bridge to split your original 16x slot into an 8x, or an 8x into a 4x, so I suggest you use a 16x slot if possible.

http://www.hardocp.com/article/2010/08/23/gtx_480_sli_pcie_bandwidth_perf_x16x16_vs_x8x8/2

The PLX "PEX 8647" is a 48 lane bridge. It does not depress the original x16 slot into a pair of x8, that's silly. Check GPU-Z (if utilizing the 6990 currently) ; each 6970 GPU is linked to a full 5.0 GT/s access point to the bridge, which means there is full bandwidth between both the CPU & GPU to GPU communication.

http://www.plxtech.com/products/expresslane/pex8647

 

[tangoseal]

They would breathe just fine if you watercooled them ..

Considering that GPUs seem to breathe underwater better than we land lubbers who require air, I agree with the quoted poster above.

If you can run 16x 16x then I would put the 6990 on the bottom and the 6970 on the top that way you get more air flow to the twin gpu card.

And FYI --- My 6990 idle temp is as follows:

Not bragging but if you are truly worried about temps it doesnt get better!

 

[sabregen]

The PLX "PEX 8647" is a 48 lane bridge. It does not depress the original x16 slot into a pair of x8, that's silly. Check GPU-Z (if utilizing the 6990 currently) ; each 6970 GPU is linked to a full 5.0 GT/s access point to the bridge, which means there is full bandwidth between both the CPU & GPU to GPU communication.

http://www.plxtech.com/products/expresslane/pex8647

any product like that, whether it supports lane switching or acts as a bridge, ultimately, has a limit on the number of lanes that it can talk to the rest of the system with.

if it says it provides 3 x16 links to devices that are plugged into it, and it's interface ix an x16 slot (as this devices is), then in between all of the cards that are plugged into it, each will get full bandwidth. However, this devices total link speed, which all 3 of the other devices that are attached to it will share, will only be x16 (total). It's not magic. I would also be very surprised if CrossfireX or SLI worked with cards contained within this devices 3 x16 links, or both inside and outside.

Yes, it allows you to plug in 3 x16 devices per physical x16 slot, but that hosting slot only has x16 bandwidth.