can you run SLI skipping the middle PCIe slot?

[Sohaltang]

I have 780TI classified in SLI. My MB has 3 PCIe slots. Currently the card are in slot 1 and 2. The bottom card blows a ton of heat into the top card. I was wondering if I could move the bottom card down to slot 3. Obviously I would need a very long SLI cable. Not sure if they make one and even if they do will the cards work correctly in slot 1 and 3?

If not I guess I need to find a Superclocked reference blower card to replace one of the classified.

 

[Attic]

Depends on your board, in your case I believe the answer is no.

SLI requires at least PCI-E x8 (2.0 or 3.0) operation and also the same speed (x8 x8 or x16 x16) AFAIK. Your motherboard won't allow x8 operation in the third slot and for you to achieve dual x8 operation you need to use slots 1 and 2.

This is different than Crossfire which will support a x4 x8 configuration. You may want to check your mobo manual, it may support Tri Fire, but not Tri Sli for similar reasons.

Have you tried direct airflow on the cards, side panel fan or fan mounted to push air parrellel through the 2 cards?

 

[Sohaltang]

This is all I found online

1. Supports AMD Quad CrossFireX™, 3-Way CrossFireX™, CrossFireX
2. Supports NVIDIA® Quad SLI™ and SLI™

 

[evilspoons]

If you're feeling adventurous you could throw a water jacket on one or both video cards and move the heat away that way. I also have my doubts about the SLI working in slot 1+3.

EDIT: Page 35 of the manual says specifically to use the slots you are already using for SLI.
EDIT 2: Wait, am I reading this right? The Asrock Z87 Extreme4 comes with a freakin dehumidifier? LOL.

 

[Bubbleawsome]

IMO you might as well try it. A long SLI bridge isn't more than $20. Right? I don't know how much they cost really. I think quad-SLI is referring to two dual-GPU cards.

 

[Sohaltang]

If you're feeling adventurous you could throw a water jacket on one or both video cards and move the heat away that way. I also have my doubts about the SLI working in slot 1+3.

EDIT: Page 35 of the manual says specifically to use the slots you are already using for SLI.
EDIT 2: Wait, am I reading this right? The Asrock Z87 Extreme4 comes with a freakin dehumidifier? LOL.

Thanks! And haha. Yeah its not really a dehumidifier. Its some sort of build in timer that turns the case fans on every now and then. I guess if you lived in a rain forest with no AC it might be useful. I disabled it

 

[cbrunny]

EDIT 2: Wait, am I reading this right? The Asrock Z87 Extreme4 comes with a freakin dehumidifier? LOL.

OMG https://www.youtube.com/watch?v=-mQfFVT4tT8#t=41

 

[lopri]

Oh haha. That is funny. It reminds me of an incident I had to wash a motherboard with a shower head and dry it for 2 days after spilling coke.

OP, find the motherboard's manual and block diagram of the board. See where the slots draw PCIe lanes. If the slot you want to use stems from the CPU (same as the first slot) then you should be able to run SLI.

 

[blackened23]

^Correct, you need to consult your motherboard manual. My suspicion is that the answer will be no unless you're on x79. X79 has much more flexibility with slot placement with CF/SLI. Mainstream chipsets such as Z97 and Z87 usually require specific slots for 2 way due to having fewer CPU PCIE lanes. The bottom slot could be connected to the PCH instead of the CPU which would limit the speed of 2 way sli or prevent it altogether. The mobo manual will answer this. Unless you have a PLX quad SLI board, and most people don't since those cost 450$,

 

[Attic]

This is all I found online

1. Supports AMD Quad CrossFireX™, 3-Way CrossFireX™, CrossFireX
2. Supports NVIDIA® Quad SLI™ and SLI™

Makes sense. SLI won't accept x4 operation where Crossfire will.

This is your constraint because PCI-E slot 3 on your board is limited to PCI Express 3.0 x4 speed.

The 3 slots will use up a max of 16x PCI Express 3.0 lanes from the CPU in either x16/0/0, x8/x8/0, or x8/x4/x4 operation modes.


For SLI you are limited to the second option above. Quad SLI would be 2 dual GPUs. You can always try in slots 1+3 and see, the added space between cards would likely lower temps substantially for the top card if you have good airflow. Though i'm fairly certain that mode is not supported for SLI.



It's possible you can set PCI Express speeds in BIOS to 3.0 2.0 1.0 and experiment with what that might get you for options of running 1.0 x8 in slot 3, never heard of this as workable option, I just noticed on my motherboard I had options to set PCI Express speeds for each slot.

 

[evilspoons]

PCIe 3.0 x4 (985 MB/s * 4 = 3940 MB/s) is faster than PCIe 1.0 x8 (250 MB/s * 8 = 2000 MB/s). Better off forcing your slot 1 and slot 3 to run in PCIe 3 x4 in that case.

 

[AkumaX]

OMG https://www.youtube.com/watch?v=-mQfFVT4tT8#t=41

related video:

https://www.youtube.com/watch?v=GvNnv7nh2Es

 

[Attic]

PCIe 3.0 x4 (985 MB/s * 4 = 3940 MB/s) is faster than PCIe 1.0 x8 (250 MB/s * 8 = 2000 MB/s). Better off forcing your slot 1 and slot 3 to run in PCIe 3 x4 in that case.

Yea that, OP just bench before and after and use GPU-Z to see what PCI Express speed each card is running at when in slots 1+2 vs 1+3.

Can't hurt to try.


Edit:
Just read this.

crossfire can work with only 4 lanes per card! eg: x8, x4, x4 and all is well as the 16 available lanes have been split in a way that Crossfire can function in!
SLI can only work with 8 lanes per card! x8, x8, x0 and all is bad as the final slot now has 0 lanes operational as the first 2 card have taken the 16 available lanes so SLI is limited to 2way.

so as the 3rd graphics card sized slot is only 4lanes wired SLI is Impossible as there are not enougth lanes available to allow SLI to function so it will be disabled! does that make more sense now?

Something I come across as often as I come across as TriSLI being doable on standard z87 boards.

 

[blackened23]

His 3rd slot may run off the PCH instead of the CPU. The PCH pcie lanes are pcie 2.0 and are designed more for addon cards such as soundcards etc rather than high speed devices. But i'm not familiar with that mobo, so.

 

[Sohaltang]

so far its not working. I found some stuff this AM about disabling usb3 to get it to work. Apparently USB3 shares that lane.

 

[kasakka]

Have you considered using a PCI-E riser to move the card away? I don't know how you'd mount it on the chassis with one but it should work.

 

[Attic]

so far its not working. I found some stuff this AM about disabling usb3 to get it to work. Apparently USB3 shares that lane.

Have you tried just a single card in the 3rd PCI-Express x16 slot? If not i'd try that and use GPU-Z to confirm the PCIExpress speed being run.

 

[Logikz]

Yeah but they'll probably run at different speeds, I think