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memory MHz/CAS latency
- Thread starter Brian23
- Start date
CheesePoofs
Diamond Member
its not possible to tell what frequency they will run at, especially without knowing what the ram is.
They should run at tighter timings at lower speeds, but again, you can't tell without knowing what the ram is.
They should run at tighter timings at lower speeds, but again, you can't tell without knowing what the ram is.
it's Mushkin. Both sticks.
Isn't there a way to calculate the speed needed to give the memory the same amount of time to complete the operation even though there are less cycles between reads/writes?
example:
it might take 23ns to read when the memory is at cas3 at 200MHz, so at 100MHz 23ns should allow for a cas1.5 setting.
Isn't there a way to calculate the speed needed to give the memory the same amount of time to complete the operation even though there are less cycles between reads/writes?
example:
it might take 23ns to read when the memory is at cas3 at 200MHz, so at 100MHz 23ns should allow for a cas1.5 setting.
Overclocking your memory is generally easier than lowering its latencies, and doing so can compensate for having higher CAS settings.
For a 200MHz DDR400 module, at CAS2, its access latency in ns is given by:
L = (1 / 200^6) * 2 = 10ns. (This is theoretical.)
At CAS3, to find what clock speed you'd need to attain the same latency in ns:
L = (1 / Clock) * 3 = 10ns.
Clock = 3 / (10^-9) = 300MHz.
So in order for a CAS3 module to attain the same access latency as a 200MHz, CAS2 module, it needs to operate at 300MHz.
I should stress access lantency here, because that's what we're dealing with.
Memory operates in bursts, that is, once the initial access penalty is over, data can be sent every clock cycle. At this point, performance is determined by clock speed alone.
There are some applications that don't care much about latency but love bandwidth, and for most, a CAS3, 300MHz module is going to outperform a CAS2, 200MHz module.
For a 200MHz DDR400 module, at CAS2, its access latency in ns is given by:
L = (1 / 200^6) * 2 = 10ns. (This is theoretical.)
At CAS3, to find what clock speed you'd need to attain the same latency in ns:
L = (1 / Clock) * 3 = 10ns.
Clock = 3 / (10^-9) = 300MHz.
So in order for a CAS3 module to attain the same access latency as a 200MHz, CAS2 module, it needs to operate at 300MHz.
I should stress access lantency here, because that's what we're dealing with.
Memory operates in bursts, that is, once the initial access penalty is over, data can be sent every clock cycle. At this point, performance is determined by clock speed alone.
There are some applications that don't care much about latency but love bandwidth, and for most, a CAS3, 300MHz module is going to outperform a CAS2, 200MHz module.
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