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Bottlenecking 250GTS SLI?

Discussion in 'Graphics Cards' started by GoogalyMoogaly, 25 Nov 2010.

  1. GoogalyMoogaly

    Soldato

    Joined: 29 Aug 2010

    Posts: 7,354

    Location: Cornwall

    Hi,

    I've been reading a fair amount lately on these forums about CPUs bottlenecking GPUs. Specifically Dual Cores vs. Quad Cores.

    This started me thinking, could my C2D E6850 @ Stock (3GHz) be bottlenecking my 250GTS SLI setup?

    I've done some runs with the free version of 3DMark06.
    With 1 1GB 250GTS card in I get about 12000 (roughly).
    With 2 1GB 250GTS in SLI I get about 14000 (again, roughly).

    Now I was under the impression that SLI scaled better than that!

    My initial thought was that since I've got an old motherboard doing SLI means I have to run both lanes at 8x instead of 16x. Since the board is old it's PCI-e v1.0 (or whatever) so I thought it was a bandwidth issue.

    Then I thought that it was because 3DMark06 only runs at 1280*1024 that it wasn't pushing the 2 cards enough to display a difference.

    But now I'm wondering if it's my CPU not feeding the cards quick enough.

    So could my E6850 be holding back my 250SLI or are 250GTS cards in SLI not that 'hungry'?

    Thanks.
     
  2. lay-z-boy

    Sgarrista

    Joined: 27 Sep 2004

    Posts: 9,231

    Location: Nantwich

    Play a game instead.
     
  3. MeatLoaf

    Capodecina

    Joined: 1 Dec 2005

    Posts: 14,079

    Location: Stoke on Trent

    Try with vantage bit really the best tests are games themselves. Grab the crysis demo and do the crysis benchmank
     
  4. chipps101

    Mobster

    Joined: 8 Jan 2010

    Posts: 3,927

    Location: Dundee

    i had a similar problem a few days ago, i was testing my new 8800gt sli test machine with an athlon x2 4200+ @ 2.5 and running the unigine tropics benchmark.

    at the default 1024 x 768 setting running the cards in sli actually scored less than a single card, by turning the resolution up to 1280 x 1024 and maxing the AA and AF settings the cpu no longer became the bottleneck and sli started scaling properly.

    try a benchmark that you can turn the graphics settings up as high as possible in and you should see the difference between 1 card and sli :)
     
  5. Rroff

    Man of Honour

    Joined: 13 Oct 2006

    Posts: 77,999

    Core 2 duo at 3gig won't (significantly) bottleneck a GTS250 SLI setup for gaming tho you won't see the max possible results from that GPU setup in benchmarks.
     
  6. allday247

    Hitman

    Joined: 22 Nov 2004

    Posts: 551

    Why are you even using that PC mate?! you have 4 other high spec gaming PC's that way surpass the components mentioned here. Ditch the old machine and use your newer PC's (btw i know a good charity you can donate those components to... me :p )
     
  7. GoogalyMoogaly

    Soldato

    Joined: 29 Aug 2010

    Posts: 7,354

    Location: Cornwall

    2 main reasons.
    1) The PC generally seems to work fine so don't want to give it away, but would like to make sure it's working as well as possible.
    2) It's the quietest PC I have and so is useful if I'm also trying to watch TV or alternating between TV and PC. But mostly reason 1.

    And it's only 2 other PCs with higher specs :)
     
  8. Peter450

    Hitman

    Joined: 26 Jan 2008

    Posts: 559

    I would say probably not that much, 250's in SLI correct me if i'm wrong, but i think there about as fast as a 280GTX or there abouts

    I think if you can get your dual core to 3.4 or more, it wont be, at 3ghz it might be a little, but only in certain games

    I had a dual core at 3.8 and a GTX 280, and gamed at 1650x1080 and felt, they were a fair match, with neither really holding the other back, except maybe in Bad Company which i hear does fair better on Quads
     
  9. GoogalyMoogaly

    Soldato

    Joined: 29 Aug 2010

    Posts: 7,354

    Location: Cornwall

    I'd like to overclock the CPU to see if that helped, but unfortunately in my wisdom all those years ago I bought a motherboard using the nForce 650i SLI chipset. It seems to be unoverclockable :(

    I think 250 SLI is basically the Nvidia 9800GX2 but with more memory. Not sure quite how that compares to the 200 series cards but I would guess 280GTX probably isn't far off.
     
  10. chipps101

    Mobster

    Joined: 8 Jan 2010

    Posts: 3,927

    Location: Dundee

    have you tried them in anything other than 3dmark yet ?

    i've been trying different resolutions and settings in tropics with my setup and the higher you turn the gfx options up the more you take the cpu out the equation and the better sli scales :)
     
  11. GoogalyMoogaly

    Soldato

    Joined: 29 Aug 2010

    Posts: 7,354

    Location: Cornwall

    No, didn't try anything else.
    If the PCI-e lane being 8x instead of 16x isn't causing an issue, I can just change the SLI profile for something to say to use only 1 GPU and that'd be the same as removing a card wouldn't it? (It's a bit awkward to keep removing the card)
     
  12. chipps101

    Mobster

    Joined: 8 Jan 2010

    Posts: 3,927

    Location: Dundee

    yeah that is what i have been doing in testing and the other card sits twiddling its thumbs when sli is disabled through the nvidia control panel.
     
  13. GoogalyMoogaly

    Soldato

    Joined: 29 Aug 2010

    Posts: 7,354

    Location: Cornwall

    Well, I didn't disable SLI, instead I just changed the SLI profile for a specific game (BC2) to be Single GPU. Judging by the temps that the cards hit that worked as one card didn't get higher than idling temps.
    The odd thing was that in BC2 I was getting pretty much identical framerates with SLI enabled and disabled!
    Slightly worrying/annoying...
     
  14. straxusii

    Mobster

    Joined: 18 May 2003

    Posts: 4,884

    Trouble is you cant run one piece of software to work out where your bottlenecks are.

    I suggest you run a few games whilst monitoring your cpu usage (task manager is fine)
     
  15. Cleeecooo

    Capodecina

    Joined: 8 Oct 2010

    Posts: 22,383

    Location: Purley - Croydon

    Why don't you upgrade to C2Q - it's the same socket. Otherwise just overclock as much as you can
     
  16. Scougar

    Capodecina

    Joined: 30 Jan 2007

    Posts: 13,408

    Location: PA, USA


    Don't have Vsync on do you?
     
  17. allday247

    Hitman

    Joined: 22 Nov 2004

    Posts: 551

    9 more posts to go aaron!
     
  18. GoogalyMoogaly

    Soldato

    Joined: 29 Aug 2010

    Posts: 7,354

    Location: Cornwall

    I do.
    The Average framerate in both cases though was around 42, so I don't think Vsync was limiting it (well, it's not like it was 60 on both, put it that way).

    Maybe I need to check the CPU usage while playing (as suggested), maybe the CPU is limiting it in both cases.
     
  19. eddie86

    Gangster

    Joined: 2 Jan 2009

    Posts: 302

    Easiest way to find out is to record your FPS then overclock your GPUs a touch, if there is no increase in FPS then the CPU is bottlenecking. You can confirm by overclocking your CPU a bit and seeing if there is an increase.

    Overclocking the GPUs a bit with Rivatuner would be the easiest, no need to worry about voltages etc if you are only increasing the speed an bit and it will give you your answer....
     
  20. chipps101

    Mobster

    Joined: 8 Jan 2010

    Posts: 3,927

    Location: Dundee


    bad company 2 will be cpu limited with your cpu, what gfx settings are you running it on ?

    run it at as high as possible gfx settings, try running hwinfo while running the game windowed and it will show you the loads on each gpu and use core temp or task manager to monitor the cpu.
     
    Last edited: 30 Nov 2010