Z97-PRO 3 way SLI Setup

de4dd0g

Distinguished
Jan 9, 2011
104
0
18,710
Hey guys, quick question. On microcenter.com (where I buy 99% of all my computer parts) http://www.microcenter.com/product/433333/Z97-Pro_Wi-Fi...

My motherboard says it supports 4 way SLI, I dont see how this is even possible.

Also I have 2 970 GTX EVGA FTW, I thought about adding a third one. Upon reading my manual I found out the bottom PCI is PCI-E 2.0 16x while the top two are PCI-E 3.0 16x.

How would this affect my SLI configuration if I got three video cards? Would this not even help me any at all because of the 2.0 PCI-E? I just don't know if having 2 970 GTX FTW in 3.0 PCI-E and 1 in 2.0 PCI-E would do anything? or would it basically operate the same? Anyways thanks in advance!
 
Solution
All Intel Core CPU's that have 16 PCIe lanes can only support a 2 way SLI. This is because Nvidia requires a minimum of 8 PCIe lanes per video card. And you cannot split 16 into 3 pieces and still have each piece have 8 or more. Beware of motherboards that do 16x/0x, 8x/4x/4x but not 8x/8x/0x. Those boards will not SLI at all.

Before we get too far along, triple SLI is where most "money doesnt matter" people stop because the return on investment keeps dropping with each card added to SLI or Crossfire. 2 cards generally add 75%+, 3 cards add 45%+, 4 cards add 15% to 25%.

If you want to go 3 way or 4 way SLI, you need one of three things.

1) X99 motherboard and CPU. Lowest end X99 CPU's come with 24 PCIe lanes, and as long as they do...
Okay so basically it's referring to video cards with two GPU's in one card? Trying to make sure I'm understanding this correctly since I've never heard of it. Maybe I'm just out of the loop on this one.

Also what about 3 way SLI, is that possible with my board? Even though the last PCI-E is 2.0 16x?
 
All Intel Core CPU's that have 16 PCIe lanes can only support a 2 way SLI. This is because Nvidia requires a minimum of 8 PCIe lanes per video card. And you cannot split 16 into 3 pieces and still have each piece have 8 or more. Beware of motherboards that do 16x/0x, 8x/4x/4x but not 8x/8x/0x. Those boards will not SLI at all.

Before we get too far along, triple SLI is where most "money doesnt matter" people stop because the return on investment keeps dropping with each card added to SLI or Crossfire. 2 cards generally add 75%+, 3 cards add 45%+, 4 cards add 15% to 25%.

If you want to go 3 way or 4 way SLI, you need one of three things.

1) X99 motherboard and CPU. Lowest end X99 CPU's come with 24 PCIe lanes, and as long as they do not take even a single PCIe lane for something else, then you can do 3 way SLI. But if they take even 1 PCIe lane for something else, you will be stuck with a maximum of 2 card SLI again. The 6 core X99 chips come with 40 PCIe lanes. These are the CPU's where you can do SLI in 3 way or 4 way.

2) Buy a pair of Dual GPU cards. Each of these cards is an SLI unto itself, and then you can pair these up.

3) There are a small number of motherboards out there that use Plex switching. Plex switching uses a special chip on the motherboard which takes certain numbers of PCIe lanes, and shares them between slots. These boards are not cheap. And they seem to be fairly rare. I just looked around... I found one...

Brand
MSI Z97 XPOWER AC

LGA 1150
Core i7 / i5 / i3 / Pentium / Celeron (LGA1150)
PCI Express 3.0 x16
5 x PCIe 3.0 x16 slots (PCI_E1, PCI_E2, PCI_E3, PCI_E5, PCI_E7)*
- The operating mode will be x0/x16/x0/x0/x0, x16/x0/x0/x16/x0,x16/x0/x0/x8/x8 or x8/x0/x8/x8/x8.*
- Support for installing up to 4 PCIe x16 expansion cards.

Its not cheap. $369.99 @ Newegg. I also will warn you that the board has a 3 egg (star) average at Newegg. But there have only been 11 comments.

In looking at the motherboard and the way the slots are lined up, if you go with 4xSLI, the 4th card would be hanging out over the end of the motherboard, so think about that when ordering a case for this monster motherboard and her 4 video cards.

http://www.newegg.com/Product/Product.aspx?Item=N82E16813130764

There may well be others out there. I just don't have the time today to keep digging. Just do a google search for "Z97 motherboard Plex" and it should find them for you.

I would also recommend that you read some reviews on these motherboards that have the plex chips. While they do their magic well, they also add some latency, and that is not always a good thing. Just understand what you are getting, and if the plex chips are likely to affect you negatively, move on up to an X99 motherboard and CPU with 40 lanes of PCIe. One other note... X99 systems require DDR4 memory, which is new, which means it costs a whole bunch more money than DDR3 would.
 
Solution
So if I'm reading and understanding your correctly the Intel i7 4790k has only 16PCIE lanes? and with my current SLI configuration it's basically using 16x as (8,8) right?

So if I put in another card of any type it would also ruin the SLI configuration?
 
Yes. The third card would either be ignored, or if the motherboard saw the 3rd card, and split the 8x that the second card had been using, the SLI would cease to function since both the second card and third card would only have 4x PCIe lanes available to them.

Either way, putting a third video card into your system cannot help you.