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# How to calculate Bandwidth?

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Whatz up people?

My question:
For example DDR400 transfers 3200Mb/s maximum right? How can I calculate for example DDR433 max transfer?

ThanX

You do a simple Calculation:
DDR200 x 8 = PC1600
DDR266 x 8 = PC2128 (PC2100)
DDR333 x 8 = PC2667 (PC2700)
DDR400 x 8 = PC3200
DDR433 x 8 = PC3464 (PC3400 or 3500 I believe?)
and so on...

actually, thats a simplified way of doing it...

clock speed X (bits per clock/8)

sdram uses a 64 bit bus
ddr ram uses a 128 bit bus (remember to divide the advertised clock speed by 2)
QDR (the p4's bus) is 256 bits (remember to divide the advertised freq by 4)

If it isn't a P6 then it isn't a procesor
110% BX fanboy
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Thank you pIII_Man :smile:
but I wasn't too wrong I hope?

not at all, that will give you the correct bandwith for ddr, it is just simplified so that it cannot be applied to any other ram tech i just wanted to put the full formula out there so that this guy wouldnt go and use the same formula to find the bandwith of his p4's bus.

If it isn't a P6 then it isn't a procesor
110% BX fanboy
a b } Memory

OMG, that discription is so confusing and misleading! 64 bits PER CYCLE, 128 bits PER CYCLE, 256 bits PER CYCLE! If you don't tell them "per cycle", people will think their 64-bit wide CPU bus is wider than it actually is, and that misunderstanding would negate my explanation that Dual Channel memory busses are 128-bits wide!

Yes, I know you mentioned bits per clock before that, but so many people know so little about this stuff that reading it like this could cause a whole lot of problems.

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pIII_Man said:
actually, thats a simplified way of doing it...

clock speed X (bits per clock/8)

sdram uses a 64 bit bus
ddr ram uses a 128 bit bus (remember to divide the advertised clock speed by 2)
QDR (the p4's bus) is 256 bits (remember to divide the advertised freq by 4)

If it isn't a P6 then it isn't a procesor
110% BX fanboy

the only thing I dont get is where from is coming /8 ? It makes all the sense but why we divide it by 8 and not other nr for examle???
a c 146 } Memory

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