Can someone explain CPU/memory overclocking on a modern MB?

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Previous overclocks I've done over the years have just involved upping a multiplier, or a FSB. I feel a little lost on my understanding how on a modern MB the memory speed/overclock comes into play?

If we took a MB running say an E6600 it would be running at 266mhz x 9 = 2.4ghz.

So if you upped the FSB to 333, there you have the CPU now running at 3.0ghz. Correct?


But what is happening with the memory during all this? And what dictates how fast it is running, or how fast it is overclocked etc? Can you set memory speed separately? Or is is based on its own FSB multiplier?

Thanks...
 
IIRC you can set memory dividers to either have the memory in sync with the CPU or asynchronous (just like in the P4 days). However, I think a P4 needed the memory to be sync'd for the CPU to get the most benefit whereas nowadays the memmory doesn't. for instance I have a E6750 (1333FSB) with 800MHz memory, and apparently I can still overclock my CPU quite abit without needing to change the speed of the memory to get maximum performance (because its already performing faster than the CPU? - correct me if I am wrong some one).
 
IIRC you can set memory dividers to either have the memory in sync with the CPU or asynchronous (just like in the P4 days). However, I think a P4 needed the memory to be sync'd for the CPU to get the most benefit whereas nowadays the memmory doesn't. for instance I have a E6750 (1333FSB) with 800MHz memory, and apparently I can still overclock my CPU quite abit without needing to change the speed of the memory to get maximum performance (because its already performing faster than the CPU? - correct me if I am wrong some one).

I think my confusion is if you have an E6600 at 266 FSB:-
266mhz x 9 = 2.4ghz.
You change the FSB to 333mhz
333mhz x 9 = 3.0ghz.
You change the FSB to 400mhz
400mhz x 9 = 3.6ghz.

What is happening to memory speeds etc before/after? Are they tied so change the FSB and the memory will be overclocked too? Or can they be overclocked separately?

What memory speeds should I be looking to get to accomodate that overclock, or indeed in the future a faster one?
 
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Memory speed will increase with your FSB, once it goes too high you can then set a divider/strap (different mobo's call this differently) to reduce the speed back to an acceptable one.

For me, i run 8x450 so if that was linked like in the P4 days my memory would be running at 900Mhz, however as i have 1066 RAM i used a different strap and got this set to 1080Mhz.

For a 3.6Ghz overclock you could then get PC-6400 RAM and run that in 1:1 (800Mhz)

Makes a lot more sense when your in front of the BIOS and can see it all changing! That should hopefully help though :)
 
Memory speed will increase with your FSB, once it goes too high you can then set a divider/strap (different mobo's call this differently) to reduce the speed back to an acceptable one.

For me, i run 8x450 so if that was linked like in the P4 days my memory would be running at 900Mhz, however as i have 1066 RAM i used a different strap and got this set to 1080Mhz.

For a 3.6Ghz overclock you could then get PC-6400 RAM and run that in 1:1 (800Mhz)

Makes a lot more sense when your in front of the BIOS and can see it all changing! That should hopefully help though :)

Aha! So in my previous example:-
An E6600 at 266 FSB:-
266mhz x 9 = 2.4ghz. Memory = 532 (266x2)
You change the FSB to 333mhz
333mhz x 9 = 3.0ghz. Memory = 666 (333x2)
You change the FSB to 400mhz
400mhz x 9 = 3.6ghz. Memory = 800 (400x2)

What does the '800FSB' mean in the chips description then? ie: The FSB by default is 266?
 
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I presume the "800FSB" chips have a 200MHz FSB (quad pumped). So 2400/200 = x12 multiplier.

My bad! Yeh, so the Q6600 1066FSB I'm looking at is:-
CPU = 9*266=2.4ghz
FSB = 4*266=1066mhz

Memory would run at on a 1:1 multiplier a 2*266=532 (PC4200)? I assume you could use other multipliers but ideally you want to aim at 1:1 with the FSB as high as possible?

Aha! All starting to make sense...

So if I can get (4GB) PC8500 memory for just £15-20 more than PC6400 memory, is it worth it?
 
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With the Q6600 I would say no. The PC6400 will be more than enough, even for a really high overclock! For example, if you got your Q6600 to run at 3.6GHz (400fsb), you would need 800MHz ram (PC6400) to keep it in sync.
 
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