Still confused over memory:

azaniah

azaniah

azaniah

Associate
Joined
11 Dec 2002
Posts
606
I know this has been hashed re-hashed in here time and again, but even after searching old topics I am a bit confused.

As I understand it, if you had a quad core chip running at 1066FSB your actual clock speed is 266Mhz, and to get to whatever speed the chip is rated at you times this by a multiplier. So for a Q6600 at stock speed this would be 266 * 9 = 2394Mhz (or 2.4Ghz near enough).
I think that means that the Q6700 which has a 2.66Ghz differs only in the fact that it can "cope" with a better multiplier of 10 (seeing as they have the same FSB).

Again, to make any given cpu run faster, you need to increase either the multiplier or the fsb (or both perhaps)

Probably that's all wrong so far - but I will plow on.

Given a Q6600 at 1066FSB, I "think" that DDR2 Memory is essentially two DDR chips running at half speed. i.e. PC4200 or DDR2-533 is essentially 2 chips running at 266Mhz. Which matches the clock speed of the machine. So in my head matching 1:1 PC4200 would be ideal for anything running 1066FSB, and PC5300 or DDR2-667 would be ideal for anything with a 1333FSB.

That is assuming that matching 1:1 is the best way to go.

So at stock speeds my thoughts are no point in anything greater than PC4200 memory.

Even with a the clock increase to 333Mhz, to overclock the cpu to 3Ghz (assuming the multiplier is locked) your still only at DDR2-667 speeds.

I guess that the new QX9650 with 1333FSB, would be 9*333Mhz = 3Ghz, matching at stock speeds DDR2-667, and again with an overclock to 400Mhz (or 3.6Ghz) you are still at only PC6400.

Why would you want PC6400 or am I missing the point here somewhere? Let alone DDR3 (not sure if I will attempt to explain my dodgy understanding of that one).

Can anyone enlighten me a bit? (Feel free to mock and laugh :))
 
Yip.

But the timings don't have a negative effect if the mhz are high enough.
 
So really the 1:1 ratio isn't something to aim for as such (although I guess 1:2 would be good also?). If your MB can cope with 1:2 (or other varients), it's stable and your memory can cope with whatever the FSB x ratio - then it's all good?
 
OK so using a 1:2 ratio and leaving most things at stock for 1066FSB would match PC8500.

If that is true, I can only guess that people recommend PC6400 so much as a cost saving, especially if your not going to overclock the cpu to any extent.

Are the negative effects using of non 1:1 1:2 ratios just that you have to fiddle with timings. There must be some trade off between latency and speed tho surely?
 
The difference between 1:1 and 1:2 is pretty small. But it's worth doing if the mhz cancel out the looser timings.

The main reason for buying faster memory is for high CPU FSB overclocking eg- 500x7 instead of 389x9 for 3.5ghz.
 
You must log in or register to reply here.
Back
Top Bottom