Some help with Corsair XMS 3200

Discussion in 'Die-hard Overclocking & Case Modifications' started by jarlaxle13, Oct 6, 2004.

  1. jarlaxle13

    jarlaxle13 Guest

    I'm running dual channel ddr400 corsair xms 3200 on an abit NF7-S 2.0 board. Everyone tells me that I should have the timings at 2.5-3-3-11. When I do put them at that I go to Sandra Memory Bandwidth test and it gives me 85% efficiency. Though when I put it on 2.5-3-3-6 it gives me 95%. Do these numbers mean anything? Also is there some magical numbers for 100% efficiency? Please help, this is like my last hope, no other forums even answers. Or they say stuff like :" Yeah, thats good."
     
  2. Reality|Bites

    Reality|Bites Ancient Guru

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    Are you sure you have Corsair XMS and not Value select?
    If yo have the XMS set the timings to 2-2-3-6 and see what you get
    Value select it either cas 2.5 or 3
     
  3. jarlaxle13

    jarlaxle13 Guest

    Yes I am sure, I payed 120 a per 512 mb. From newegg, with the black heatspreaders. I thought that AMD boards like 2.5 cas, not the rated 2. As far as I can tell eveyone says that they have it at 2.5 for amd.
     
  4. Reality|Bites

    Reality|Bites Ancient Guru

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    Oh you bought the C2 memory and not the LL or XL
    Well go with what work then. run a few games with a tras of 6 then a tras of 11, see if you notice any difference.
     

  5. jarlaxle13

    jarlaxle13 Guest

    How will i notice the difference? When its at 2.5-3-3-6 it gives me 95% with 2.5-3-3-11 it gives me 85%. Do these numbers mean anything?
     
  6. Reality|Bites

    Reality|Bites Ancient Guru

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    Just tried the test myself, Running @ 2-2-2-11 I get 95% and running 2-2-2-6 I get 94%.
    Just use the 2-3-3-6 then if it runs better for you.
     
  7. jarlaxle13

    jarlaxle13 Guest

    So you leave it at 95% right? No way to get it up to 100% is there? What if I did 2.5-2-2-6. Is that considered better?
     
  8. Reality|Bites

    Reality|Bites Ancient Guru

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    Yeah I leave it at 2-2-2-11 giving 95%, I don't think you can get 100% as windows is already using some memory(guessing don't really know)
    I don't think your memory can run 2.5-2-2-6. Maybe 2.5-2-3-6.
     
  9. Jflo22

    Jflo22 Active Member

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    just for info purposes, I have the exact same ram in 2x 512 chips and I run them in a P4 board at 2-2-2-5 and they seem to work great. 8 hour run on Prim95. Like you said, could be diff on AMD board but I just wanted to throw that info out.
     
    Last edited: Oct 6, 2004
  10. jarlaxle13

    jarlaxle13 Guest

    Hmmm, soon as I get home I will try 2.5-2-2-5. If that fails, onto 2.5-2-3-6. Can anyone tell me what Tighter timings actually do? Will I really notice a difference from 2.5-3-3-6 and 2.5-2-2-5? Also how does dual channel fit into? It says each stick is capable of 3200mbit and sandra says i'm getting 3035. So that x 2 = 6070 out of a possible 6400. Where is the rest going?
     

  11. Leo Demetriou

    Leo Demetriou Member

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    What do these numbers mean?
    Where do you change them?
    And what are the recommended settings for my RAM?

    Thanks.
     
  12. Reality|Bites

    Reality|Bites Ancient Guru

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  13. Leo Demetriou

    Leo Demetriou Member

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  14. Reality|Bites

    Reality|Bites Ancient Guru

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    Well you would change the timings in your bios(press delete at the post screen) Probably under advanced settings or something like that.

    First of all, what is CAS?

    "CAS" is short for "Column Address Strobe". A DRAM memory can be thought of as a matrix, kind of like a spreadsheet with memory cells instead of numbers and formulas. Like the spreadsheet, each cell has a row address and a column address. As you might have guessed, there is also a RAS signal, which is shorthand for "Row Address Strobe".

    And, what do you mean by "latency"?

    Latency refers to the time that you are waiting to get what you need. Merriam-Webster dictionary defines it as "the interval between stimulus and response".

    Now, how does CAS work?

    To understand this let's walk through a simplified version of how the memory controller actually reads the memory. First, the chip set accesses the ROW of the memory matrix by putting an address on the memory's address pins and activating the RAS signal. Then, we have to wait a few clock cycles (known as RAS-to-CAS Delay). Then, the column address is put on the address pins, and the CAS signal is activated, to access the correct COLUMN of the memory matrix. Then, we wait a few clock cycles -- THIS IS KNOWN AS CAS LATENCY! -- and then the data appears on the pins of the RAM.

    So, for CAS-2 you wait 2 clock cycles and for CAS-3 you wait 3 clock cycles?

    Bingo!

    So, CAS-2 is 33% faster than CAS-3?

    Whoa, not so fast! There are a LOT of other factors in the memory performance. Here are a few of the main ones:

    Sometimes you have to move to a different row in memory. This means activating RAS, waiting RAS-to-CAS delay, then doing the CAS latency thing.
    Other times, you do a "burst" read, when you pull in a lot of data in one big block. In that case, CAS is only activated ONCE, at the beginning of the burst.
    Also, don't forget the most important thing: processors have big caches! The cache is where the processor stores recently accessed instructions and data. The cache "hit rate", i.e., the percentage of times the processor finds the information it needs in its own cache, is typically greater than 95%!
    OK, OK, so what's the bottom line?

    So, the bottom line is, moving from CAS-3 to CAS-2 will offer a percentage performance increase in the low single digits for most applications. Programs which are known to be memory intensive (you gamers might know of some...) will see the best improvement.

    The other thing to keep in mind is that CAS-2 memory will run FASTER than CAS-3 memory. So, if you're thinking of overclocking your system (now or in the future), CAS-2 is your best bet for speed and stability.

    Buy CAS-2 if [1] you want to wring the last bit of performance out of your system, or [2] you're thinking of overclocking, either now or in the future, or [3] it costs the same as CAS-3, which it sometimes does...

    Otherwise, CAS-3 memory should meet your requirements


    instruction sequence

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    Bios

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    Last edited: Oct 7, 2004
  15. Leo Demetriou

    Leo Demetriou Member

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  16. [X]Pyro

    [X]Pyro Master Guru

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    very well put Reality!
     

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