Threadripper, PCI Express, and multiple GPUs

Quartz · 13 Aug 2017 at 17:49

Paging @Kaapstad !

One of the plus points of Threadripper - and Epyc - is the large number of PCI Express lanes. I would like to see someone test the effect of this with multiple GPUs, both Radeon and Geforce, in 2, 3, and 4 card configurations. I suspect that there will be a modest difference but I'd like actual numbers.

8 Pack · 13 Aug 2017 at 20:08

I tried all this time ago can try to post up tomorrow. It's very easy for me to run again.

Minstadave · 13 Aug 2017 at 20:10

Problem with multi card setups, at least Crossfire anyway, is not a lack on bandwidth, just god awful driver support.

Quartz · 13 Aug 2017 at 20:50

8 Pack said:
I tried all this time ago can try to post up tomorrow. It's very easy for me to run again.

I didn't know earlier CPUs and chipsets supported so many PCI Express lanes.

8 Pack · 13 Aug 2017 at 22:02

I tried TR in June. Also 4 way SLI back then.

Obviously Intel X Chipset has supported four GPU's for many years.

Quartz · 13 Aug 2017 at 22:10

8 Pack said:
Obviously Intel X Chipset has supported four GPU's for many years.

The Intel CPUs have never had 64 PCI Express lanes with x16 support, have they?

But if you could post a link to your results, I'd be most interested.

8 Pack · 13 Aug 2017 at 22:11

On Asus Ws board you can have 4x16 via plx chip for sure. On that board you can run 7 gpu 8X no issues.

Kaapstad · 14 Aug 2017 at 08:18

Quartz said:
Paging @Kaapstad !

One of the plus points of Threadripper - and Epyc - is the large number of PCI Express lanes. I would like to see someone test the effect of this with multiple GPUs, both Radeon and Geforce, in 2, 3, and 4 card configurations. I suspect that there will be a modest difference but I'd like actual numbers.

8 pack is the man for this as he has both the knowledge and access to the hardware.

What I do find with mGPU setups is CPU clockspeed is far more important than whether you are running PCI-E 3.0 X16 or X8.

Panos · 14 Aug 2017 at 12:55

Isn't sli capped above 2 cards, requiring extra licence to make it work?

Minstadave said:
Problem with multi card setups, at least Crossfire anyway, is not a lack on bandwidth, just god awful driver support.

AMD drivers are fine years now, and so is the cross fire support also, with more new games supporting it than SLI.

Minstadave · 14 Aug 2017 at 12:59

They certainly weren't fine for Xfire last year. Every new release wasn't supported for months and even when it was performance was poor and bugs still visible.

I hadn't heard there had been a significant improvement since.

Quartz · 15 Aug 2017 at 09:52

I'm having zero problems with my SLI Titans in games.