Do I need an SLI bridge?

[Erixson]

Do I need an sli bridge? I have an intel 750 series PCI-E ssd, Z-170 Deluxe motherboard, and 2 EVGA Geforce Gtx 1080 FTW and I was wondering if I needed a bridge. If I do need a bridge which one? (I was planning on putting the 2 gpus on the bottom two slots)

 

[greens]

Not only do you need a bridge - you need a HB Bridge.

You can only use the slots your motherboard says you can use. You'll need to check and see what configurations your board supports x16/x16 or x8/x8 in....

And there we have a problem! Who advised you on your build?

You're lacking lanes. Skylake has 16 PCIE lanes available to the CPU. Your GPUs will want 8 each, for a total of 16. Running the GPUs at 4 or 2 will greatly reduce their performance.

But you have a PCIE SSD which wants 4 lanes for itself. So that means you only have 12 lanes leftover... Which means resource allocation errors or stagnated GPU speeds are in your future.

TLDR - you need a High Bandwidth Bridge, but that doesn't matter because you're using too many PCIE lanes for a skylake build. 🙁

 

[azaran]

*edit for math reasons
The HB bridge is right, but the PCIe lane math is wrong. Skylake affords 20PCIe lanes + 16 PCIe lanes for GPU. So with an SLI setup (x8 + x8) and your SSD (x4) you're going to be fine. Your manual should have the correct information of what can be plugged in to which slot and/or turn off what feature by having the PCIe SSD installed.

 

[firefoxx04]

Correct, skylake has 20 lanes. You still need to make sure the GPUs are going in x8 or x16 slots. The slots might physically be x16 but they need to actually run at x8 or x16. It is likely that only two of them actually support x8.

 

[Erixson]

Ok, Lets say I take out 1 of the gpus are there any remaining issues?

 

[azaran]

Ok, Lets say I take out 1 of the gpus are there any remaining issues?

No no, by all means keep the GPUs in. Other than needing the correct SLI bridge you're golden. With one GPU you're running at x16 speed. When you pop a second one in for SLI you're running both at x8 + x8. Thats as it should be.

 

[Erixson]

Alright, What bridge do I need?

 

[azaran]

OK "need' is kinda dependent on your setup. If you're gaming at 1080, you can use the old school flexible SLI bridges that comes with your gear. Even up to 1440 I belive you can use it. But if you're planning on most FPS and 1440 or higher, you're going to want to get a High Bandwidth Bridge. You're sporting 1080 SLI cards, so we're all kinda assuming your going with a high rez monitor. Otherwise you're blowing a lot of cash on something you wont even notice.

You're running EVGA cards, so you might as well stick to that branding. Pick your appropriate one from here.
http://www.evga.com/products/productlist.aspx?type=14&family=SLI+Bridge&chipset=HB+Bridge

Newegg has them for a few bucks cheaper, and they also have the Nvidia ones as well.
https://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=50001402%2050001441&IsNodeId=1&Description=HB%20Bridge&bop=And&Order=PRICE&PageSize=36

 

[Erixson]

Thank You! How do I tell what slot spacing to get?

 

[azaran]

Thank You! How do I tell what slot spacing to get?

Take a look here
http://www.evga.com/articles/01020/evga-pro-sli-bridge-hb/

 

[azaran]

Also make sure to read the manual to tell if the bottom two slots of your motherboard are the correct slots to put your GPUs