8x vs 16x issue

I have two hd4850s in my hand....

I have a p5q deluxe, thus if I want to run this in crossfire I would have to sacrifice 16x speeds. With some games not taking advantage of crossfire I would assume those games in crossfire would actually be worse in performance than a single 4850. My question is how much of a hit would I take with games that do not take advantage of crossfire.
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  1. what resolution are you playing at first?

    I know somebody posted the links to the sites that have reviewed this issue b4, i thought it was like less than 10-5%

    Not a huge deal if you think about it....
  2. FrozenGpu said:
    what resolution are you playing at first?

    I know somebody posted the links to the sites that have reviewed this issue b4, i thought it was like less than 10-5%

    Not a huge deal if you think about it....

    its a 22 inch samsung native rez at 1680 x 1050.
  3. fchowd0696 said:
    its a 22 inch samsung native rez at 1680 x 1050.


    if u search this forum for like P45 or something similar u will find those charts that show what i was talking about, unless of course u play FSX, and only really that then the frame rate loss is pretty small...

    To be brutally honest, I wouldn't be bothered by it too much, b/c it doesn't have the impact say a 4x slot would have, which is quite noticeable, this is much less noticeable, so go ahead!
  4. I think it's almost a total non- issue. Crossfire HD4850 would be even better, but look how 8800GTS 512MB SLI performs the same on a 750i SLI (8x/8x) as on 780i SLI (16x/16x):
    http://www.firingsquad.com/hardware/evga_nforce_750i_sli_ftw_review/page11.asp

    I researched this when buying a mobo for 8800GT SLI plans and found little to no difference in the reviews I could find. So I decided to save money and buy a 650i vs 680i at the time. Eventually this should change, but not sure if we are even really there yet with GTX 280 SLI in current games.
  5. If you've already got the cards and the board, don't sweat it. It looks like at worst it'll give you a 10%ish decrease in performance (compared to dual x16 links), but probably not for most instances. It shouldn't really perform worse than a single 4850 almost ever.
  6. dirtmountain said:

    I have a hard time believing there is such a difference (edit: just from 8x vs 16x) with crossfire 4850's when SLI shows zero difference at 19x12 4xaa even. Very strange yet interesting results I would like to explore this or see it explored in depth.


    Here is the techspot 650i/680i comparison with 8800GTX SLI:
    http://www.techspot.com/review/45-nvidia-nforce-650i-sli-vs-680i-sli/page4.html
  7. http://www.anandtech.com/video/showdoc.aspx?i=3341&p=20

    Check out COD4. I find it interesting just how good crossfire HD4870 did on the X48 vs a single 4870 on 790i. > 100% scaling shows how good X48 is in comparison.
  8. I agree with you Pauldh, it seemed a much bigger hit then it should take. I just can't find much more info on it though. My bet is that is will a very small effect.
  9. Only other P45 vs X48 crossfire I have seen was HD3870's and low res..... nothing that could challenge techspots findings.


    Imagine if it proves to be an accurate picture!!! If it is true, forget 8x/8x crossfire HD48x0 series.
  10. Also the P45 boards use second gen PCI-e which, in theory, have twice the bandwidth so you'll still, again in theory, be getting x16 first gen speeds on each port. Since the 4850 can't fully saturate a first gen PCI-e X16 slot I think it won't effect your performance.

    Edit: At resolutions you can actually play at the 4850 can't saturate a first gen x16 port.
  11. JDocs said:
    Also the P45 boards use second gen PCI-e which, in theory, have twice the bandwidth so you'll still, again in theory, be getting x16 first gen speeds on each port. Since the 4850 can't fully saturate a first gen PCI-e X16 slot I think it won't effect your performance.

    Edit: At resolutions you can actually play at the 4850 can't saturate a first gen x16 port.


    See that's the thing, it really doesn't saturate it as much as PCI-Express 1.0 did, well running 8x/8x mode as opposed to 16x/16x.
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