Multi headed build with AMD

mh46107

Honorable
Aug 26, 2012
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A little back story. Currently I'm running a multiheaded build with an i7 2600, 2 GTX 660s and 16gb of ram. If you don't know what multiheaded means here, it is basically two users running separate OSs simultaneously. I use a Linux based hypervisor to host two windows VMs, and with PCI passthrough I can dedicate an entire gpu to each instance and divvy up the 8 threads and ram.

My computer is getting pretty old, so I was planning a new build with the same idea, however this time I wanted to have up to 4 users. My plan was to get 4 GTX 1070s and pair them with the AMD R7 1800x, so each user can essentially get 4 threads. However, it seems that the x370 motherboards only support up to 2 GPUs. Can anyone confirm this for me, and if confirmed possibly make a suggestion on what cpu/Mobo can support 4 GPUs?

Thank you very much
 
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Barty1884

Retired Moderator
Looking at an X370 board at ranodom (the Crosshair VI Hero), there are 3x PCIe 3.0 x16 slots (which should all operate in x8) and a single PCIe 2.0 x16 (so, essentially another x8). Should be able to support 4 GPUs.
https://www.newegg.com/Product/Product.aspx?Item=N82E16813132963&nm_mc=AFC-C8Junction&cm_mmc=AFC-C8Junction-PCPartPicker,%20LLC-_-na-_-na-_-na&cm_sp=&AID=10446076&PID=3938566&SID=

CFx and SLI support are limited to two cards (I believe), but for your uses, you don't need them to operate in tandem, you need them individually..... and I suspect you can achieve this.
 


That board will support 3 amd card but not 3 Nvidia cards. The 3.0 slots will run at 8x and the 2.0 only runs at 4x.

If you're wanting 4 cards you have to look at the 2011v3 boards. 90% of consumer boards don't offer more then sli/CF, its not until you get into the enthusiast boards like the x58 and x99 board that you can start to get 3 and 4 video cards installed.

I run a x58 Asus rampage 3 extreme with 4 670 superclock+ on it at work runs at 3 way sli with a 4 to power 2 extra monitors.


* I stand corrected on this, looks like the z170 and z270 boards from intel do offer support for 4 card @8x per slot.
 

Barty1884

Retired Moderator


My bad, misread it as 4 slots.

Out of curiosity, why would they support 3x AMD but only 2x nVidia?

I appreciate it cannot run >2way SLI, but for workloads that don't require SLI enabled (like this), should it not be able to run them? (albeit in this case, no help as it's only 3). Just curious.
 


Nvidia cards have to run on 16x and 8x. AMD cards are able to drop down to 4x and still be able to operate.
 

Barty1884

Retired Moderator


According to this test, a GTX 1080 can be run adequately in an x4 slot.....
https://www.techpowerup.com/reviews/NVIDIA/GeForce_GTX_1080_PCI_Express_Scaling/
Incidentally, it appears to have a ~0.5FPS difference vs an x8 or x16...... at least in gaming.

My understanding has always been nVidia cards require x8 slots for SLI, whereas AMD can operate in CFx via an x4.
Nothing that actually stops the cards from running (albeit not in SLI) by utilizing an x4.
 

USAFRet

Titan
Moderator


You should consider writing up a tutorial on this.
Many people come here wondering "How..."

Parts, software, performance, etc, etc.
 

mh46107

Honorable
Aug 26, 2012
44
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Nice name, I did 7 years AD and currently in ANG... I've thought about making a tutorial, especially since there seems to be multiple ways to go now, the first time I did something like this was in 2010 using a quad core AMD proc with like two AMD 5450s and there wasn't much guidance or many options. When I actually get around to putting this together I will document it

 

USAFRet

Titan
Moderator


Is your username any reflection on your AFSC?
 

mh46107

Honorable
Aug 26, 2012
44
0
10,540


Thank you for all of the advice. After more research, it would seem that i need 40 PCI-E lanes to run 4 concurrent Nvidia GPUs, and unfortunately Ryzen is capped at 24 lanes. My next issue then became locating a minimum 8 core w/ hyperthreading CPU with 40 lanes, which landed me on the i7-6900k. Unfortunately, the i7-6900k doesn't have integrated graphics, and I didn't have any luck finding an x99 board with an onboard gpu AND 4 PCIE slots.

My potential solution is here:

https://www.newegg.com/Product/Product.aspx?Item=N82E16813157557

and if i pair it with a

https://www.newegg.com/Product/Product.aspx?Item=9SIA1YH4RC2276&cm_re=xeon-_-19-117-629-_-Product

then I won't be cutting into the water loop I'm planning on, also not sure if that mobo can handle the 6900ks 140w TDP. For gaming I would assume the 6900k would absolutely demolish the xeon, but gaming is really only a fraction of what this PC will be used for
 
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