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Thread: How memory timings on A64's affect performance - The truth.

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    Investigating CAS


    Synthetic Benchmarks

    200x12 / 2-2-2-10 :
    Everest Latency Benchmark : 47.2ns
    Sandra Soft 2005 Bandwidth : 6070 / 6027

    200x12 / 2.5-2-2-10 :
    Everest Latency Benchmark : 50.8ns
    Sandra Soft 2005 Bandwidth : 6055 / 6012

    200x12 / 3-2-2-10 :
    Everest Latency Benchmark : 53.1ns
    Sandra Soft 2005 Bandwidth : 6048 / 5994

    As you can see, going from CAS2 to CAS2.5 will lose you about 3ns in latency (7.6%). Going from CAS2.5 to CAS3 will hit you for about another 3ns.

    And how does this affect your bandwidth? Not much overall. The total difference from CAS2 to CAS3 is only a 22 / 33 decrease (0.25% / 0.25%). And from CAS2.5 to CAS3 it's only 1%! That definately isn't much in the grand scheme of things, as you'll see when we get to real world gaming.




    Competitive Benchmarks

    200x12 / 2-2-2-10 :
    3DMark 2001 : 351.3 / 156.2
    3DMark 2005 : 6312
    Aquamark 3 : 77661

    200x12 / 2.5-2-2-10 :
    3DMark 2001 : 344.5 / 153.3
    3DMark 2005 : 6304
    Aquamark 3 : 76749

    200x12 / 3-2-2-10 :
    3DMark 2001 : 338.2 / 150.9
    3DMark 2005 : 6309
    Aquamark 3 : 75755

    (Note : Most competitive benchers on the A64 platform make use of A64 Tweaker by CodeRed, I'd just like to note that I did not use that utility at all for any of these benchmarks. CAS timings were set in the BIOS. Lobby Low and Lobby High are the scores shown. A64 Tweaker shot for specific settings on all benchmarks can be found here.)

    Interesting results we see here. Competitive Benchmarks really do get affected by things as specific as your ram timings, which most competitive benchmarkers already know I didn't use 2003 for this test because it's essentially in between 2001 and 2005 as far as CPU / Ram dependance.

    3DMark 2001 showed a large decrease when switching CAS timings. Going from CAS2 to CAS2.5 decreased Lobby Low by 6.8 (1.97%)FPS ! As benchers know, this is a huge decrease. Going from CAS2.5 to CAS3 dropped it another 6.3 FPS (1.86%). These may seem like nothing to most people, but when it comes to competitive benchmarking, almost 2% is a huge, huge difference. In Lobby High we saw the same drop happen, we lost 5.7 FPS (3.51%) going from CAS2 to CAS3.

    3DMark 2005 showed slight differences which are within the margin of error, so we can basically ignore all those tests. This just goes to show you that 3DMark 2005 is essentially entirely GPU as of now. In 4 years it will probably just as CPU bound as 3DMark 2001 has become.

    Aquamark 3 showed interesting results as well. I never thought Aquamark 3 was this dependant on things as specific as ram timings. We see that from CAS2 to CAS2.5 we drop an astounding 912 (1.18%) points. Further, from CAS2.5 to CAS3 we drop another 994 (1.31%) points. The total difference from CAS2 to CAS3 is 1906 (2.52%) points. That is a huge difference, if you ask me when it comes to competitive benchmarking.

    And now, we move on to the true test, real world performance.



    Real World Performance

    200x12 / 2-2-2-10 :
    VST Low : 198 FPS
    Doom 3 Low : 144.2 FPS

    VST High : 102.74 FPS
    Doom 3 High : 61 FPS


    200x12 / 2.5-2-2-10 :
    VST Low : 198 FPS
    Doom 3 Low : 143.7 FPS

    VST High : 101.7 FPS
    Doom 3 High : 61 FPS


    200x12 / 3-2-2-10 :
    VST Low : 193 FPS
    Doom 3 Low : 142.2 FPS

    VST High : 101.07 FPS
    Doom 3 High : 61 FPS


    Very interesting results we see here. Even when we're running at lowest settings, taxing the CPU / Ram much more so than the video card, we see almost the exact same numbers throughout.

    Doom 3 Low barely budged. It isn't within margin of error, it is indeed because of the CAS timings, but a total of 2 FPS difference from CAS2 to CAS3 is pretty significant when it comes to showing that timings don't matter that much in real world gaming.

    Doom 3 High was entirely GPU. Frames don't change at all, why? Well, something as insignificant as ram timings won't change anything if all the work is being put on your GPU, so we see absolutely no performance decrease.

    VST Low gave almost the same results as Doom 3 Low. Now, on CAS3 it did seem to drop more than from CAS2 to CAS2.5, and I did rerun the test to make sure, and it hit 193 each time. Even so, a 5 FPS drop when you're dealing with settings that will never be used real world don't have much weight, in my opinion.

    VST High also gave interesting results. This is real world, this is what you'll see while playing. From CAS2 to CAS2.5, we lost 1 FPS. Oh no!! Not a whole frame! Going from CAS2.5 to CAS3 dropped us not even a single frame per second, 0.63 if you want to get technical. I think we can all agree that that means nothing in terms of real world performance. Overall, going from CAS2 to CAS3 dropped us approximately 1.63 FPS.



    Conclusions

    Well, overall, I think we got some interesting results. On forums a lot I'll hear people ask 'Should I get this 2.5-3-3 ram or this 3-3-3 ram?'. In most cases, the 2.5-3-3 ram will be a decent amount more expensive than the 3-3-3 ram. And most people get the answer of 'Go for the 2.5 ram, it's worth it'. I think after the tests given above, we should really start questioning that.

    For Competitive Benchers
    I don't think I need to say much here. If you bench for sport, you already know what I've told you. Timings do matter, and they matter a reasonable amount. The difference at the same Mhz between CAS2 and CAS2.5 even is a reasonable amount. The difference between CAS2 to CAS3 is even more pronounced, and as we all know, 500 points in any benchmark can make or break a world record. Paying the extra $50-$100 for CAS2 ram instead of CAS2.5 is definately worth it. But as I said, if you're a bencher, you already know all of this and probably have some nice sticks of BH5 or TCCD at your side already, so I don't think I need to say much more on this front.

    For Gamers (especially those on a budget)
    Here's what it really all comes down to. If you're a gamer with a newer PC, you're most likely on the A64 platform. The question of timings comes into play a lot when deciding your PC components. I even previously would tell people to spring for the CAS2 over the CAS3, thinking it would indeed help with performance. Keep in mind, this is specifically dealing with CAS only. If you have the choice between 2-2-2 and 3-2-2 ram (which won't happen often), then I think you can see that the extra money usually isn't worth it if you're an average gamer. After the tests above, I really have to question myself. Is it really worth it? For a budget gamer, $50-$100 is a pretty decent amount of cash to smack down for some CAS2 ram as opposed to some CAS3 ram. Is it truely worth it? I guess that's up to the gamer themselves, but overall I think we can come to the conclusion that the answer is no. $50 extra for 1 FPS under normal gaming conditions is not something most people would spring for. Even when it's entirely CPU / Ram dependant, we barely see a 3 FPS difference. This is entirely negligable, I think we can agree. I myself was surprised at how little difference in the real world ram timings had an effect. Update - Keep in mind, this is CAS only.



    Final Thoughts

    Well, when it comes to CAS only, I think it's clear that for real world performance, CAS doesn't mean a thing. For benching, of course it does. And for synthetic benchmarks, you will see a performance decrease, but it's extremely minimal (well under 100mb/s from CAS2 to CAS3). Scroll down for more benchmark results regarding other timings. But as a final answer for CAS only, it has no real world performance decrease when changing from CAS2 to CAS3 (keeping all other timings equal).
    Last edited by cuddles; 12-28-2004 at 02:04 AM.
    .:: S939 FX-53 (240x11 1:1) | 2x512 Ballistix DDR400 (2.5-3-2-10) | MSI K8N Neo2 Platinum (1.36b) | x800 Pro VIVO -> XT (575/590) | 21" Viewsonic G220fb | Lian Li PC75b ::.

    Aquamark 3 : 84367
    3DMark 2001 : 31717
    3DMark 2003 : 14313
    3DMark 2005 : 6580

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