x16 vs x8 pci-e motherboard/GPU setup does it matter?

Thu Dec 27, 2012 5:39 am

Bought 3 580 GTX for my MSI Z77A-G45 mobo only to find I can only run 2 of the 3 580's. After spending quite a while looking in the forum and online trying to decide on whether it is worth it to upgrade to a LGA 2011 CPU to support the 3.0 x16 on 3-4 card slots I wonder if this is the right time to upgrade or wait?

I read through a few very technical explanations and comparisons on this but really they are geared toward gaming rather then rendering with Octane so I wonder if anyone here can tell me if it will be worth upgrading my mobo to a ASRock X79 or ASUS Rampage IV Extreme in order take advantage of using 3-4 GTX cards in Octane. Does it take advantage of the x16 PCI-E as opposed to x 8PCI-E ?

If I do this upgrade it will also require the LGA 2011 CPU and I will do it if it is worth it but if not I'll stay with my config.

Any thoughts would be appreciated.

Thu Dec 27, 2012 8:54 am

It makes very little, or no, difference.

Thu Dec 27, 2012 2:38 pm

steveps3 wrote:It makes very little, or no, difference.

Maybe the x8 vs x16 pci-e slots may not make much of a difference now as regards to bandwidth saturation that is one issue (Article: A GTX 560 does not fully saturate PCIe x4 (version 2.0). http://www.techpowerup.com/reviews/Inte ... s_Scaling/ but certainly adding 2 or more GPU's will effect performance this is a second issue.

Most of the research out there to date is for SLI performance which Octane does not take advantage of. My question is does or will Octane take advantage of (3) GTX 690 in (3) pci-e slots running at x16 bandwidth, or will a x16/x16/x8 setup or a x16/x8/x4 setup perform the same?

Thu Dec 27, 2012 5:05 pm

Buzby, from everything I have gathered (and please, someone lmk if I am very wrong) this is not anything like gaming - where you are trying to get over 60 fps on Modern Warfare 3 or Crysis 2 - but rather all scene data is loaded onto the card(s) and then they do their thing (strictly on the cuda cores) which they are passing back to octane at a much smaller clip than a hardcore game requires. In other words, it appears that the i/o with Octane is not anything like a modern game that needs the constant back and forth massive throughput from the game and then spit out to your monitor.

I have not seen anyone say that if a 690 et al is running at x4 etc (because of the number of cards installed) it is going to be handicapped in some significant way. It is what is happening inside the gtx/cuda cards (once scenes are loaded) that the real magic is happening... er, not how quickly scene/assets are loaded or the render viewport is updated.

Again, someone correct me (or articulate this better) if I am wrong.

Thu Dec 27, 2012 5:20 pm

x8 or x16 -this only matters a little bit for loading time. When the scene is in the VRam it shouldn't affect the render performance at all.

Thu Dec 27, 2012 7:51 pm

Refracty wrote:x8 or x16 -this only matters a little bit for loading time. When the scene is in the VRam it shouldn't affect the render performance at all.

Thank you both for your replies. So no point in worrying about the new pci-e 3.0 x16 hype with regards to Octane in the foreseeable future. This settles the slot issue. It appears that the rendering question then has been answered by and large by any decent/recent mobo that will accommodate the most graphics cards so any decent 2.0 pci-e slot should do.

Back to the issue, of which mobo to get. I know this has had numerous threads but I think it has been narrowed down now to what is relevant.

If I am missing something on this please comment. I will be searching for mobos that will support at least 4 GTX 580 GPUs reliably.

Thu Dec 27, 2012 9:40 pm

In my signature you can see the mobo I have with 4x 580... There are others ofcourse.
Greetz,

Thu Dec 27, 2012 9:56 pm

I myself was very much leaning toward MSI Big Bang II for my next build... however, going that route would require a XL ATX case - which the pickins are pretty slim for those.. the CoolerMaster Cosmos II would be the obvious choice - jesus, does that look like a sweet-ass case!!.. but I have a beautiful, very expensive, monolithic and gynormous Lian-Li PC-V2100 Plus - that I spent something like $450 on just four years ago... and dammit - I am determined to build my next workstation in this same case!

Edit: Rappet - thanks for the heads-up on Asus Rampage IV!! This clearly looks like the one I will want.. it is only Extended ATX (which my current Asus MB is and will fit right into my existing case) and not XL ATX like the Big Bang II. Nice!.. I need to tweak my shopping cart!

But regardless, it will be real nice to get away from dual cpu workstations.. I have had 4 now -- my god are they expensive to build and replace parts for. ECC ram alone is so expensive next to regular ram... buying two cpus.. motherboards don't have the bells/whistles of high-end gaming mbs... did I mention I f-ing love octane and GPU rendering in general?!!!

Fri Dec 28, 2012 3:52 am

rappet wrote:In my signature you can see the mobo I have with 4x 580... There are others ofcourse.
Greetz,

Rappet, yes I almost got that (Asus Rampage IV Extreme) but I didnt want to change out my CPU so I finally purchased the ASUS P8B WS LGA 1155 Intel C206 ATX Intel Xeon E3 Server/Workstation Motherboard.

Only recently I purchased the MSI Z77A G45/LGA 1155 3770 CPU combo to work with C4D rendering but this was before I knew about Octane. I wanted to keep my LGA 1155 3770 CPU so I went with the ASUS P8B WS. (Got a great deal at only $149 bucks) I am hoping to fit all 4 GTX cards in here 3 GTX 580 and 1 GTX 670. Looks like my new MSI Z77A G45 is going on Ebay..

Fri Dec 28, 2012 4:00 am

FrankPooleFloating wrote:I myself was very much leaning toward MSI Big Bang II for my next build... however, going that route would require a XL ATX case - which the pickins are pretty slim for those.. the CoolerMaster Cosmos II would be the obvious choice - jesus, does that look like a sweet-ass case!!.. but I have a beautiful, very expensive, monolithic and gynormous Lian-Li PC-V2100 Plus - that I spent something like $450 on just four years ago... and dammit - I am determined to build my next workstation in this same case!

Edit: Rappet - thanks for the heads-up on Asus Rampage IV!! This clearly looks like the one I will want.. it is only Extended ATX (which my current Asus MB is and will fit right into my existing case) and not XL ATX like the Big Bang II. Nice!.. I need to tweak my shopping cart!

But regardless, it will be real nice to get away from dual cpu workstations.. I have had 4 now -- my god are they expensive to build and replace parts for. ECC ram alone is so expensive next to regular ram... buying two cpus.. motherboards don't have the bells/whistles of high-end gaming mbs... did I mention I f-ing love octane and GPU rendering in general?!!!

I have the CoolerMaster Cosmos and it is a rockin' case! I bought it about 3 years ago and it performs so well I never needed an upgrade. It handles everything I have ever thrown at it. Still really clean inside the case and minimum dust. Thanks for the info on the CoolerMaster Cosmos II.
So glad for Octane, never could get into the dual CPU workstation good riddance and long live intelligent unbiased rendering