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3 GPUs - which slots?

Retired
Not applicable
So I currently have 2x 5870 cards populating the first and third PCI-E slots - 16x/empty/16x/empty.

When reading the R3E manual, when using 3x GPUs, it recommends that I use the first, third, and fourth PCI-E slots - 16x/empty/8x/8x.

Is this configuration required? Will using the first 3 slots cause any problems, ie. 8x/8x/16x/empty?

The reason why I ask is because this is a water cooled rig. Using that 4th slot will be difficult with the Koolance full cover motherboard block I am currently using. Also if I use the first three slots, does that mean I need to plug all my monitors in the third GPU instead of the first one?

Any help is greatly appreciated!
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7 REPLIES 7

Hapatingjaky
Level 8
You must use 1, 3 and 4 when using Tri-Crossfire with dual slot solutions.

That said, you can use 1, 2 and 3 but the middle card may overheat due to AMD's design of the 5870 cooler. the intake would only be from the back of the card and may be insufficient to cool the GPU. Spacing with 1, 3, 4 gives gaps so that air can pass evenly for each card. But even in slot 3 and 4 it will be a tight fit. Its up to you though.
Intel Core i7 5930K @ 4.8GHz, Asus Rampave V Extreme U3.1, Kingston HyperX Fury 2666MHz 32GB DDR4 ( 4x8GB ), Nvidia GeForce Titan-X SLI, Creative Labs E3 USB Soundcard, Samsung 950 Pro 512GB M.2 NVME, Corsair AXi 1500i PSU, Corsair 900D, Corsair K95 RGB Keyboard, Logitech Proteus Core Mouse, Acer Predator X34 @ 100Hz, Sennheiser Gamer Zero, Windows 10 Professional

Retired
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Thanks for the input, hapatinjaky! I guess my question was more directed at 16x/empty/8x/8x vs. 8x/8x/16x/empty configuration.
Heat isn't an issue as all three cards will be water cooled.

itcrashed wrote:
Thanks for the input, hapatinjaky! I guess my question was more directed at 16x/empty/8x/8x vs. 8x/8x/16x/empty configuration.
Heat isn't an issue as all three cards will be water cooled.


Yes the Rampage III will only do 8x8x8x in a TRI-Crossfire or TRI-SLI Configuration. The only time you will notice a difference compared to 16x16x16x is you plan to do Eyefinity or Nvidia Surround and game at 5760x1080. Take a look at this article that HardOCP did regarding performance differences between 8x vs 16x PCI-E speed:

http://www.hardocp.com/article/2010/08/16/sli_cfx_pcie_bandwidth_perf_x16x16_vs_x16x8/

There are 4 or 5 articles that HardOCP published regaruding this and its a good read. Basically you will notice no performance decrease between 8x and 16x until you go higher then 2600x1600 resolution.
Intel Core i7 5930K @ 4.8GHz, Asus Rampave V Extreme U3.1, Kingston HyperX Fury 2666MHz 32GB DDR4 ( 4x8GB ), Nvidia GeForce Titan-X SLI, Creative Labs E3 USB Soundcard, Samsung 950 Pro 512GB M.2 NVME, Corsair AXi 1500i PSU, Corsair 900D, Corsair K95 RGB Keyboard, Logitech Proteus Core Mouse, Acer Predator X34 @ 100Hz, Sennheiser Gamer Zero, Windows 10 Professional

Retired
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you will be running x8 on all lanes if you run quad gpu setups for CFX
x16 gen2 empty x8 gen 2 x8 gen2 if you run tri card setup

the difference is the bandwidth of
x8 Gen2(2.5GT/S) vs x16 Gen1(2.5GT/S) vs x16 Gen2(5GT/S)

so when people say with a NF200 you have x16 on all lanes, it is a x16 Gen1 which has the same bandwidth as a x8 Gen2. it is only the power delivery of a x16.

Retired
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Brian@ASUS wrote:
you will be running x8 on all lanes if you run quad gpu setups for CFX
x16 gen2 empty x8 gen 2 x8 gen2 if you run tri card setup

the difference is the bandwidth of
x8 Gen2(2.5GT/S) vs x16 Gen1(2.5GT/S) vs x16 Gen2(5GT/S)

so when people say with a NF200 you have x16 on all lanes, it is a x16 Gen1 which has the same bandwidth as a x8 Gen2. it is only the power delivery of a x16.


So Brian, does it matter which configuration I go with?
Which one is better GPU1/GPU2/GPU3/empty or GPU1/empty/GPU2/GPU3?

Thanks for your feedback!

itcrashed wrote:
So Brian, does it matter which configuration I go with?
Which one is better GPU1/GPU2/GPU3/empty or GPU1/empty/GPU2/GPU3?

Thanks for your feedback!


Use 1, 3 and 4:

1=16x
3=8x
4=8x

In TRI-SLI/TRI-Crossfire config
Intel Core i7 5930K @ 4.8GHz, Asus Rampave V Extreme U3.1, Kingston HyperX Fury 2666MHz 32GB DDR4 ( 4x8GB ), Nvidia GeForce Titan-X SLI, Creative Labs E3 USB Soundcard, Samsung 950 Pro 512GB M.2 NVME, Corsair AXi 1500i PSU, Corsair 900D, Corsair K95 RGB Keyboard, Logitech Proteus Core Mouse, Acer Predator X34 @ 100Hz, Sennheiser Gamer Zero, Windows 10 Professional

Retired
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The manual says 1 3 4 but I use 1 2 3. My games run fine and I don't notice any game play differences. It looks better on 123 anyways If I find time we will try and do a slot configuration test to see if there is a difference.