How does FSB, memory and CPU speeds all relate?

[Frosteh]

For the Core 2 Duo chips...

I know that memory speed is often quoted as the DDR values (533, 667, 800,1000 which is really 266, 333, 400 and 500) so the Non-DDR speeds multiplied by the CPU's multiplyer is the clock speed for the CPU (for example E6600 is 266x9 = 2394 or ~2.4Ghz).

Now the "quad pumped" part has always confused me, we're talking 4x the Non-DDR speed of the RAM which is 266x4 = 1066Mhz.

However when you use faster ram to overclock, i.e pruchasing some 667/333 like I have done means I can get my CPU upto 333*9 ~= 3Ghz

But does this mean the front side bus between the north bridge and the memory is now 4x333 = 1332Mhz or is this controlled seperately?

Also aren't the other busses, the PCI express and the PCI busses fractions of the main FSB, in which case don't they get higher also? I'm assuming most mobo's can lock these speeds in place rather than it strictly being a ratio, so it's always the right speed?

Anyhow a little light shed on the situation would be great, my E6600 and mobo is already here but I'm waiting for some replacement RAM since the OCZ stuff I got doesn't work in the motherboard

Thanks for any help!

 

[BinarySynapse]

Memory speed and FSB is semi-independant. Meaning that the FSB is the base clock (the non-quad pumped value) for which everything else it set too. If you're running a 1:1 divider then every bump you give the FSB will give an equal bump in the memory clock. If you're using a 5:4 divider (i,e DDR2-667 speed on a 266FSB). then the memory will run at 5/4 (or 125%) of the FSB's base clock.

The CPU's final speed is calculated by multiplying the FSB base clock by it's internal multiplier (i,e if the CPU is hasa 9x multi and the FSB is 266 then you get 2.4GHz)

Chaning the memory speed in bios does nothing to the FSB, but just changes which divider the system uses to calculate the memory's base clock with. Increaseing the FSB's speed directly increases both the memory's and CPU's speed.

 

[Frosteh]

So when overclocking I want to change the FSB speeds up and not just the RAM?

Can I leave the RAM as detect by speed or set it as 1:1 or does it work in a different way?

How does this effect the quad pumped value of 1066, will this increase as the size of the FSB is increased?

*edit*

Also, thanks for the help so far!

 

[BinarySynapse]

So when overclocking I want to change the FSB speeds up and not just the RAM?

Can I leave the RAM as detect by speed or set it as 1:1 or does it work in a different way?

How does this effect the quad pumped value of 1066, will this increase as the size of the FSB is increased?

*edit*

Also, thanks for the help so far!

If you want to push your whole system as far as it can go, then yes set your RAM:FSB to 1:1 divider. If you set your RAM to Auto or SPD then it will set the memory to whatever the highest setting that is programmed into the slowest module's SPD chip. That means that you'll most likely end up hitting a wall with the RAM long before you get the max performance out of your system.

The quad value means nothing really. All it says is that Intel CPUs can send and recieve data four times for every tick of the FSB's base clock. This gives an apparent speed of four times what the actual speed is, but it really means nothing in the world of overclocking since it not something that can be changed.