CPU Multiplier

[NeilV]

Hi All
Some of you may have seen my other posts, I'm still deep in the unpleasent brown stuff but I don't want to drag this thread down with me sooooo......

Could someone explain the advantage of a higher FSB & lower multiplier. I've ssen a few OC'ers who have their CPU multipliers @ 8 or 7 and with their FSB up @ 400. Is this for a situation when the CPU is not very happy with a maxed oout multipler?

I'm running into some problems OCing my Q6600 but I've not actually tried using a lower multiplier as I assumed that it was the FSB/RAM that was making the OC unstable.

Sorry if this topic has been covered in another thread, if so just show me the door :lol:

Thanks

NeilV

 

[jitpublisher]

Its been done to death, but in a nut shell, when you raise the multiplier, you are only overclocking the CPU, when you raise the bus speed, you are overclocking everything that runs on the bus, basically, everything.
Not every CPU has an unlocked multiplier, if your cpu's multiplier is of the locked variety, as most are, you can only overclock by raising the bus. This can pose a lot of other issues to come into play, as all the components running on the bus don't always react well to being overclocked. Thus you have the memory divider, so you can regulate memory speed in relation to the bus speed, a PCI clock lock which will keep your PCI and PCIe bus running at the right speed no matter where you put your buss speed, and with AMD, you have the hypertransport bus which is yet another way to control memory to CPU speed via yet another bus speed setting.
Now, years ago, bus speeds were relatively slow, so overclocking by working with the bus would net you much, much better overall performance than by just raising the cpu speed via the cpu mulitplier. But today, with our double and quad pumped bus speeds, and memory controllers on the CPU rather than the motherboard, and large CPU caches, raising the bus speed does not in its self net you much gain at all over simply raising the multiplier on the cpu. But as stated, if the cpu is of a locked multiplier variety, then you have no course but to go the bus route. If the multiplier is locked, you cannot raise it above the stock setting, but you can lower it. If you are a talented overclocker, and understand completely all those tricky settings in your BIOS, you can do some pretty wild things with bus speeds and coax a lot of performance out of a locked lower end cpu. But it takes time and determination.
I find it is much easier to just buy a cpu this day in age with an unlocked multiplier, makes things much easier.

 

[NeilV]

thank you jitpublisher, that has to be the most concise, illuminating and intelligeble answer I have ever seen.

I don't seem to be able to select it as an answer but maybe I'm doing something wrong :lol:

Thanks again.