Lewis wrote:Hi Guys!
Has any of you with 1.x extenders (cheap USB ones and/or those expensive Amefltec) experienced slowdowns/issues on Octane 3.03xx ?
I've tested a lot last days and as soon as i plug in my 1x USB riser card my GPU on riser card is 30-35% slower than same GPU directly on Motherbard. When i plug 3 GPUs on MB + 4th GPU on PCI-E 1x extender all GPUs slowdown (less OB score/points) ? Octane 3.03xx just uses less GPU load than it usually does with 3 GPUs or even 2 GPUs ?
My GTX 1080 at Motherboard gives OB score 125-128 and same GPU at PCI-E extender gives 81-85 points ???
Thanks
Hi Lewis,
This is not your imagination. I don't know the mechanics why, but at least with USB risers and splitters, there is a diminishing return per GPU as you add more, despite the overall linear rise as you add more GPU.
This appears to the case with the USB risers and splitters, I am not sure how it works with straight motherboard connections.
Here below I have a more scientific analysis of the relationship between USB riser 1x vs motherboard at 16x.
Some background, my rig has 1 Titan X in case on motherboard.
Then I have 12 Titan Z (6 cards) connected via Amfeltec Clusters, powered via 2 external PSUs.
Then I also have 2 Titan X cards connected via risers, powered via a 3rd external PSU.
I can never run all 15 GPU at same time as my BIOS currently can only give me 13GPU cores at once. So I either run in one of 2 'modes':
(A) 1 Titan X mobo and 12 Titan Z Amfeltec, and
(B) 1 Titan X mobo and 2 Titan X USB riser
So, with the Titan X's I have the following 3 cards:
(1) Titan X on mobo @16X
(2) Titan X on USB 3.0 Riser @1x
(3) Titan X Pascal on USB Riser 3.0 @1x
So, I positioned a test scene where I got a 100 s/px score with the Titan X on the motherboard 16x, to benchmark, with no overclockling.
Next here is the 'regular' Titan X on the USB Riser 1x (no overclock). Gave ~75-80 s/px
Then here is the 'regular' Titan X on the USB Riser 1x, overclocked +150 MHz. Gave ~83 s/px
Last, the Titan Titan X Pascal on the USB Riser 1x (no overclock). Gave ~100 s/px
Looking at this, I see that there was a 20-25% drop for the same Titan X card on the riser. Overclocking the card +150 MHz bought me another ~5-8%.
What is interesting then is the Pascal, which is a higher powered version of the 'regular' Titan X, matched almost exactly the 'regular' card on the motherboard. So, I am thinking if I saw a 20-25% drop for the riser Titan X, likely the Pascal would be 20-25% greater if connected 16x on the motherboard (I am imagining a score of ~133).
The moral of the story is, yes, the cards will drop 25% on a USB riser, but you can either overclock it to compensate, or if you get a Pascal version of the same card, you can pretend it's a 'regular' card on the motherboard.
Win 10 Pro 64, Xeon E5-2687W v2 (8x 3.40GHz), G.Skill 64 GB DDR3-2400, ASRock X79 Extreme 11
Mobo: 1 Titan RTX, 1 Titan Xp
External: 6 Titan X Pascal, 2 GTX Titan X
Plugs: Enterprise