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The consensus on GT200 overclcoking gains

Discussion in 'NVIDIA' started by wolf, Jan 26, 2009.

  1. wolf

    wolf Performance Enthusiast

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    ok so as per the title i want a consensus from members on some particular OC numbers from some cards in the GT200 series, exactly 3 questions to be precise.

    1. What clock speeds does a GTX 260 core 216 need to attain GTX 280 actual performance

    2. What clock speeds does a GTX 260 core 192 need to attain GTX 280 actual performance.

    I do realize that some situations the physical (ie framebuffer) difference will prohibit attaining 280 performance, but on the whole (1920x1200 and below) i know 280 actual performance is possible.

    My thoughts on those 2 clock frequencies are about the same with a varying shader clock only. my guesses are.

    GTX260 core216 - core: 684mhz - shader: 1436 mhz - Memory: 2430mhz
    GTX260 core192 - core: 684mhz - shader: 1620 mhz - Memory: 2430mhz

    3. what clocks on a 295 to get GTX280 SLi actual performance.

    My guess is,

    core: 684mhz - shader: 1296 mhz - Memory: 2430mhz

    All of these numbers are based on the theoretical peak specs of all cards, like core clock X rops gets you pixel fillrate, calculating mem bandwith and finally shader compute power.

    I have found interestingly that at the aforementioned guess speeds, the GTX260 + 295 cards i have tested equal their rivals or surpass them due to a clock speed advantage.

    i realize if you overclock the 280 (SLi) they will naturally win out but its an interesting question.

    thoughts?
     
  2. OnBoard

    OnBoard New Member

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  3. wolf

    wolf Performance Enthusiast

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    My results, like i mentioned are based off the theoretical peak numbers on each card, this is how i came to those results

    GTX 280 core: 602mhz x 32 ROPS = 19.2 G/Pixels

    GTX 260/295 core: 576mhz x 28 ROPS = 16.1 G/Pixels

    GTX 260/295 core: 684mhz x 28 ROPS= 19.1 G/Pixels <- equals 280 actual

    ---------------------------------------------

    GTX 280 shader: 240 x (MADD (2 FLOPs) + MUL (1 FLOP) x 1296mhz = 933 G/Flops

    GTX 260 shader: 216 x (MADD (2 FLOPs) + MUL (1 FLOP) x 1242mhz = 810 G/Flops

    GTX 260 shader: 192 x (MADD (2 FLOPs) + MUL (1 FLOP) x 1242mhz = 720 G/Flops

    GTX 260 shader: 216 x (MADD (2 FLOPs) + MUL (1 FLOP) x 1436mhz = 930 G/Flops<- equals 280 actual

    GTX 260 shader: 192 x (MADD (2 FLOPs) + MUL (1 FLOP) x 1620mhz = 933 G/Flops<- equals 280 actual


    ---------------------------------------------

    GTX 280 memory: 1105mhz x 128 = 141.7 G/Bps

    GTX 260/295 memory: 999mhz x 115.2 = 111.9 G/Bps

    GTX 260/295 memory: 1215mhz x 115.2 = 140 G/Bps <- equals 280 actual


    ....... so really if a GTX280 were at stock speeds, it should only ever overtake if memory becomes a limitation, is that right? and in fact some games will prove faster as a fair few favor a faster core speed.
     
  4. OnBoard

    OnBoard New Member

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    Yep, same way as higher clocked dual core beats quad, if the game can't take advantage of all that it's given for. I don't mind overclocked GTX 260 beating my upcoming GTX 280, as I got it cheaper than GTX 260 price :)
     
  5. wolf

    wolf Performance Enthusiast

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    well considering on the GTX295 i have all of the Sp's, i reckon @ 675/1458/2304 shes pretty spot onto GTX280 SLi performance.
     

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