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1:1 ratio

By LinkedKube
Mar 23, 2007
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  1. Trying to figure out how to get a 1 to 1 fsb ratio with my ram, kinda lost, been reading and cant find any hints. Currently my bus speed is 343, and my ram is running at 900mhz ddr2 6400. cpuz tells me my fsb to dram ratio is currently 10:13. I did well in math, but been tryin to switch it up and still nothing..
  2. Mirob

    Mirob TechSpot Paladin Posts: 841

    DDR2-533 is 1:1, some BIOS list it as 267MHz.
  3. KingCody

    KingCody TS Guru Posts: 1,568   +7

    Hi supersmashbrada,

    DDR2's effective speed (transfer rate) is double it's actual operating speed. if your FSB is set to 343MHz, then to achieve 1:1 your RAM would have to run at 343MHz as well (343MHz = DDR2-686).

    your specific mobo/BIOS will determine how to achieve a 1:1 ratio:

    • if your BIOS lets you simply type in a target RAM speed then you simply change "auto" to "manual" and type in 343 (the BIOS will choose the appropriate multiplier/divider to achieve as close as possible to the target speed.

    • if your BIOS makes you select a ratio (listed as DDR2-533, DDR2-800, etc) than you'll have to calculate what the resulting ratio of each setting is. since the default FSB of an E6300 is 266MHz/267MHz, the 1:1 setting will always be DDR2-533. since the ratio doesn't change, if you set it to DDR2-533 and raise the FSB, the RAM will always operate in sync with the FSB (1:1)

    NOTE: since your RAM is capable of running faster, then you should test different speeds (via benchmarks) to see what gives the best performance. you may benefit more from the extra bandwidth than with a 1:1 ratio.

    cheers :wave:
  4. LinkedKube

    LinkedKube TechSpot Project Baby Topic Starter Posts: 4,265   +41

  5. KingCody

    KingCody TS Guru Posts: 1,568   +7

    glad I could help... good luck with your overclock :D
  6. HPCE_Larry

    HPCE_Larry TS Rookie Posts: 189

    Similar question. If i get a c2duo and they have a fsb of 1066, then doesn't that mean i would have to get ram that ran at 1066 ddr2 to get a 1:1 ratio?
  7. Mirob

    Mirob TechSpot Paladin Posts: 841

    The Intel bus is quad pumped, so the actual speed is 267MHz times four. DDR is double data rate so the real speed is half the ratted DDR. 1:1 is DDR 533.
  8. KingCody

    KingCody TS Guru Posts: 1,568   +7

    that would be true if those were the actual speeds. but they are not actual speeds, they are effective speeds (transfer rates) due to quad pumping and double data.

    "1:1" refers to the actual clock speed, not the effective transfer rate. for this reason an Intel FSB with an effective transfer rate of 1066MT/s and DDR2 with an effective transfer rate of 533MT/s both operate at an actual clock speed of 266MHz/267MHz

    that was probably a typo, but to avoid confusion... the effective speed is 266/267 x4, resulting in a transfer rate of ~1066MT/s. the actual clock speed is 266MHz/267MHz.

    :wave:
  9. HPCE_Larry

    HPCE_Larry TS Rookie Posts: 189

    thank you very much.
  10. hkuve

    hkuve TS Rookie

    what about the latency ?? if my fsb @ 300 and the dram freq @ 800 mhz ???

    and if my fsb@360 , the dram will not be @ 800 , it will be @ 825?? is that correct if we running @ 825 and what about the latency ??
  11. KingCody

    KingCody TS Guru Posts: 1,568   +7

    hkuve,

    I think you are confusing effective transfer rates with actual RAM frequency. when configuring FSB and RAM speeds, the effective transfer rate is irrelevant. you should only worry about the actual frequency. (read above posts if you need clarification).

    In BIOS's that use a ratio setting to control the RAM frequency, the ratios are calculated based on the default speeds. at default Core-2-Duo speeds:
    • DDR2-533 (266 actual) would be a ratio of 1:1
    • DDR2-667 (333 actual) would be a ratio of 4:5
    • DDR2-800 (400 actual) would be a ratio of 2:3
    • DDR2-1066 (533 actual) would be a ratio of 1:2
    • etc...

    the DDR2-800 setting would be a FSB:RAM ratio of 2:3, which would result in a RAM frequency of ~450MHz (900MT/s)

    no, at the DDR2-800 setting (ratio 2:3) a FSB of 360 would result in a RAM frequency of ~540MHz (1080MT/s)

    latency is basically the RAM's internal speed and has nothing to do with it's external speed (or "dram frequency").

    :wave:
     
  12. LinkedKube

    LinkedKube TechSpot Project Baby Topic Starter Posts: 4,265   +41



    Best information given in this thread thus far.
  13. MetalX

    MetalX TechSpot Chancellor Posts: 1,909

    Kingcody and Mirob have it right.

    Just a question... is DDR2-1066 an official speed like DDR2-533, DDR2-667, and DDR2-800?
  14. Captain828

    Captain828 TS Guru Posts: 277

    what if I oc a c2d to a bus of 400MHz (1600Mhz)?
    whouldn't i have 1:1 ratio with some 400Mhz (800MHz) RAM?
  15. Mirob

    Mirob TechSpot Paladin Posts: 841

    Yes, that is exactly right.
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