P4C800-E Deluxe - CPU speed vs Timming vs Memory speed?

Discussion in 'Asus' started by NEM, Feb 7, 2004.

  1. NEM

    NEM Guest


    I've spend a bit of time going through and writing down all the various
    setting combinations for OC'ing the system listed below. It boils down
    to CPU speed vs memory speed. Which is more important in your opinion?

    For example...

    CPU |FSB |CAS |MB/s
    3375 |225 (DDR450) |2-3-2-6-4 |2929


    CPU |FSB |CAS |MB/s
    3405 |227 (DDR454) |2.5-3-2-6-4 |2893

    ....I know, I know, there isn't a lot of differences, but these are
    rather extreme example settings. The differences are more apparent with
    lower OC'ing, something of which I plan to eventually use.

    System currently runs 40c under full load using stock heat sink (lapped
    and AS5 used) and Motherboard at 27c using the above settings. All
    memory test were run using Test#5 repeatedly (30+ passes) in Memtest86+

    Asus P4C800-E Deluxe
    Mushkin PC3500 Level II 512MBx4
    P4 3.0c
    Antec PLUS 1080AMG case

    Thanks for reading,
    NEM, Feb 7, 2004
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  2. NEM

    Paul Guest

    Generally speaking, "clock rate is king". Whatever you lose via having
    to increase the CAS setting, you can more than make up by the ability to
    increase clock rate (at least until something else breaks).

    So, for example, people buy PC4000 memory, because it runs at DDR500.
    DDR500 is 25% more than DDR400, but the memory might have to run at
    CAS 3 instead of CAS 2 . The CAS increase costs 10% of your performance
    increase, leaving you with a net increase of 15%.

    In your example, at the point you are forced to change from CAS2 to
    CAS2.5, that is a bad point to leave the clock at. This is because
    you've taken a hit on performance due to the CAS increasing, but you
    haven't increased the clock enough to "pay back" what the CAS change
    has cost you.

    Clock speed alone should be giving you a "linear" performance ramp,
    but every time CAS changes, that is a downward "stair-step". The
    sum of those two functions gives you the memory bandwidth
    performance curve.

    Because of the fact that clock rate is king, that is why people
    are happy to buy 3-4-4-8 memory for PC4000, because the higher clock
    rate makes the memory timings irrelevant. (As long as you are harnessing
    the extended clock rate range of course - buying PC4000 memory and
    running it at DDR400 doesn't make too much sense. If a user plans on
    staying at stock speed, the money would be better spent on a PC3200
    low-CAS memory.)

    Paul, Feb 7, 2004
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  3. NEM

    NEM Guest

    Hi Paul,

    On Feb 08 2004, Paul wrote:

    But isn't true that at this time chips are not made specifically for
    anything above PC3200. If that is the case, then PC4000 is PC3200
    memory, but with lose SPD settings.

    Speaking of the SPD, I found that the SPD was read wrong by the
    motherboard, so manual timings were almost certainly needed.

    The default SPD settings for the Mushkin PC3500 is 2-3-3-7. Mushkin
    advertises the sticks at 2-2-2-?, I've read that the last digit is
    suppose to be a 5, but I didn't have any luck with 2-2-2-5, so I bumped
    it up to 6 and started to have error free results.

    In my situation, I found one stick to be a little weaker then the other
    three (even though they were purchased all at the same time as two
    matched pairs). It wasn't until I took it off of auto SPD, and started
    manually setting the timings that the weak stick fell in line with the
    other three. I'm also told, that because of the amount of memory (2GB),
    that I am fortunate to have all four working well together.
    I stopped test at that point because of the increase in CPU speed/heat.
    I felt that going further then 10 percent would be shortening the live
    of the CPU unless I took further steps to cool it down.

    So in my example, I would probably be better to leave it at 3.375GHz
    since that is the last working combination with the faster 2-3-2-6

    After 31 tests, so far these are the working results according to the
    testing method mentioned above...

    CPU |FSB |CAS |MB/s |Volts
    3060 |204 (DDR408) |2-2-2-6-8 |2781 |2.75
    3255 |217 (DDR434) |2-2-2-6-8 |2825 |2.75
    3270 |218 (DDR436) |2-2-2-6-4 |2838 |2.75
    3284 |219 (DDR436) |2-2-2-6-4 |2850 |2.75
    3314 |221 (DDR440) |2.5-2-2-6-4 |2815 |2.75
    3329 |222 (DDR442) |2.5-2-2-6-4 |2828 |2.85
    3345 |223 (DDR446) |2.5-2-2-6-4 |2842 |2.85
    3345 |223 (DDR446) |2-2-2-6-4 |2903 |2.85
    3359 |224 (DDR446) |2-2-2-6-4 |2916 |2.85
    3375 |225 (DDR450) |2-2-2-6-4 |2929 |2.85
    3390 |226 (DDR452) |2.5-2-2-6-4 |2880 |2.85
    3405 |227 (DDR454) |2.5-2-2-6-4 |2893 |2.85

    ....I've also locked the AGP/PCI to 66.66/33.33 and left the divider to
    Like a sawtooth wave. Going to 2.5 is like being dropped off the edge of
    I didn't think there was much point doing that with the stock processor
    speed of 3.0GHz. If I had a 2.4GHz that might be something to do because
    of the mulitpler and divider, so I felt that I could squeese out the the
    Mushkin PC3500 BH5s. Was that incorrect thinking?

    Thanks Paul.
    NEM, Feb 8, 2004
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