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fsb versus memory speed

post #1 of 7
Thread Starter 
how do they compare? is ddr2 533 the equivilent to 1066mhz fsb or what? i need this information because i plan on overclocking a lot... and i want to be able to get the best timings out of it as well.

like if i ran 1066mhz fsb would the memory be bottlenecked by running my memory at ddr2 800? ddr2 667?

also, is there a point at which the fsb causes instability - such as hypertransport for AMD processors?
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post #2 of 7
Nope. The FSB on intels are "quad-pumped". Your effective FSB on your C2D is 266 mhz, therefore, if your ram runs at 533mhz, it will be equal to your ram speed.
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post #3 of 7
Thread Starter 
Quote:
Originally Posted by Wankerfx
Nope. The FSB on intels are "quad-pumped". Your effective FSB on your C2D is 266 mhz, therefore, if your ram runs at 533mhz, it will be equal to your ram speed.
this reply confused me.
you mean if my ram runs at 533mhz its the equivilent of my FSB?

so if i were running it at ddr2 667 it would be bottlenecked by the fsb?

i guess i'll have to do my own testing once i get the psu and its up and running... lol
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post #4 of 7
These examples are all 1:1, FSB:RAM -

DDR2 533 (533mhz), FSB266 (quadpumped: 1066mhz)

DDR2 667 (667mhz), FSB333 (quadpumped: 1333mhz)

DDR2 800 (800mhz), FSB400 (quadpumped: 1600mhz)

DDR2 1066 (1066mhz), FSB533 (quadpumped: 2133mhz)
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post #5 of 7
533 divided by 2 = 266, remember its Double Data Rate 2 memory.

At stock settings, you are running a 1:1 ratio. If you up your FSB to say 300, then its forcing your DDR2 533 to run at DDR2 600 (which I doubt it could do). This leads to system instability.

This is why you use memory dividers.

If you were to have bought DDR667 (333mhz effective) you wouldn't have to use a divider until you reach a 333 FSB. (theoretically). But if you're memory is "high quality".

Like......
Mushkin, G.Skill HZ, OCZ Gold/Plat, Corsair XMS, Kingston HyperX....then you probably could overclock the memory....to run past its designed speed. Thus eliminating the use for a divider, and speeding up bandwith.
    
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post #6 of 7
Thread Starter 
nahh, my ram is ddr2 667 and my motherboards standard is ddr2 800...
so default being ddr2 667 and 1066mhz fsb, i would want to run it on a ddr2 533 divider, overclocking or not correct?
at least to add stability?

i understand how overclocking works haha - so running ddr2 667 1066mhz fsb is really pointless because the fsb would bottleneck my ram then, right?
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Heisenberg
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post #7 of 7
Correct......use ckp64s chart he posted above to figure out what FSB matches what RAM speed. Running the RAM faster than the FSB has little effect outside of some benchmarks.
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