Memory PC 2100 PC 2700 PC 3100 PC 3700

pbrandaopbrandao
edited June 2005 in Hardware
I need information abouth this formula for obtain speed in MHZ from memory DDR PC 2100 PC 2700 PC 3100 PC 3700
:confused:

Comments

  • MedlockMedlock Miramar, Florida Member
    edited May 2005
    Divide by 16.

    PC2100 ~133MHz
    PC2700 ~166MHz
    PC3200 -200MHz
    PC3700 ~233MHz
    PC4000 -250MHz
    :)
  • pbrandaopbrandao
    edited May 2005
    why divide by 16 ?.
  • ThraxThrax 🐌 Austin, TX Icrontian
    edited May 2005
    Because it does 2 8 byte calculations per cycle, or 16.
  • qparadoxqparadox Vancouver, BC
    edited May 2005
    The PC # rating is the theoretical bandwidth of the memory in MB/s.

    So to calculate the PC number, X, for ram of Y MHz you do

    X = Y Megacycles/s * 2 bits / cycle (since DDR) * 64 bits (this is the width of the bus) * 1 byte / 8 bits (this is just the way it is) ->

    X=16 Y MegaBytes/s

    So to go backwards you do Y=X/16.

    I hope you like math :).
  • madmatmadmat
    edited May 2005
    Personally, I'd just divide by 16 or if you want it's speed (as in ddr400) divide by 8 instead, example, pc3200/8=400. Simple, no?
  • MedlockMedlock Miramar, Florida Member
    edited May 2005
    :wow: I forget where I heard divide by 16 but I guess that explains it. I think... :scratch:
  • sfleurietsfleuriet Texas New
    edited June 2005
    TheGr81 wrote:
    Divide by 16.

    PC2100 ~133MHz
    PC2700 ~166MHz
    PC3200 -200MHz
    PC3700 ~233MHz
    PC4000 -250MHz
    :)

    I could've sworn that my PC3200s were 333mhz..

    well wait- i have one stick of PC2700 and one stick of PC3200 - that ADDS up to 366mhz (if thats how if would work..?) so maybe thats why I'm thinking of instead of 333mhz.
  • shwaipshwaip bluffin' with my muffin Icrontian
    edited June 2005
    all of your memory runs at the lowest speed of any one stick - you're running it all at PC2700 = DDR 333 = 166 MHz
  • sfleurietsfleuriet Texas New
    edited June 2005
    ohhhh yeah thats right!! i forgot about that completely... ok so its 332mhz mathematically, but my BIOS just says 333mhz. ok thanks
  • shwaipshwaip bluffin' with my muffin Icrontian
    edited June 2005
    it's 166.6 (repeating).

    166.6 * 2 = 333.3
  • sfleurietsfleuriet Texas New
    edited June 2005
    ah ok so it does simply add up. cool
  • shwaipshwaip bluffin' with my muffin Icrontian
    edited June 2005
    They don't add. All the memory runs at the lowest speed...the speed of your PC3200 (normally DDR400) is PC2700 (DDR333) in your system, because you're running it with PC2700.
  • sfleurietsfleuriet Texas New
    edited June 2005
    yeah i know the 3200 is going the speed of the 2700. so two 2700s added together, makes my 333mhz.
  • shwaipshwaip bluffin' with my muffin Icrontian
    edited June 2005
    pilotwings119 wrote:
    yeah i know the 3200 is going the speed of the 2700. so two 2700s added together, makes my 333mhz.

    One stick of PC2700 runs at DDR333.
    Two sticks of PC2700 run at DDR333.
    Three sticks of PC2700 run at DDR333.
    Four sticks of PC2700 run at DDR333.
    Five sticks of PC2700 run at DDR333.
    Six sticks of PC2700 run at DDR333.
    Seven sticks of PC2700 run at DDR333.
    Eight sticks of PC2700 run at DDR333.

    Frequency has nothing to do with number of sticks.

    Think of your cpu and memory as two buckets of water (data) with a pipe between them. Adding more memory just makes the memory "bucket" larger. Increasing the frequency of the bus (going from DDR333 to DDR400) is like making the pipe bigger.
  • sfleurietsfleuriet Texas New
    edited June 2005
    ok
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