What's more important, CPU Multiplier or CPU FSB?

[Zapablast05]

Ok, so I finally started to follow directions for overclocking instead of enter and pray. My CPU's max multiplier is 12x and I max out at 3.0GHz without slowing my RAM down. I did what this one guy did that reviewed my motherboard, start from 5x and gradually work my way up until you max out. So, I started with 5x and my RAM running at DDR2 400 (200MHz) and my CPU FSB at 240MHz and my HT Link at 5x. It went good. Then I started to go up, adding the multiplier by increments of 1 until I couldn't go anymore. I lowered my HT Link to 3x to let me go higher. I reached a maximum of 290MHz FSB at 11x, RAM at (I think, I'm not sure how to calculate RAM speed) 270MHz. I tried getting my RAM to full DDR2 800 speed and I achieved it by lowering my FSB to 260MHz, 11x CPU multi, and 4x HT, and I got my RAM running at 535MHz (WOW) but I ran into some BSOD's, so I just bumped my voltage up about +.250v and my CPU voltage to 1.45 and I got things stable. But then I started getting BAD_POOL_HEADER, partmgr.sys, and STOP: 0x000000F7 BSOD's. Could that be because I'm clocking too high?

Back to the main idea that forced me to post this. Is it better to have really fast CPU FSB with a lowered multiplier? In my case, it would be 260MHz at 11x. Or is it better to have my multiplier maxed out at 12x and my CPU FSB maxed out at 250MHz? What would be faster and what's more important?

[sytaylor]

With a higher FSB your whole machine is going faster whilst the CPU is roughly the same. So you will see better results from a higher FSB most of the time, but it is a balancing act, some apps require more RAW cpu crunching.

[Revs]

^ What Sy said.

Find your highest FSB with a low multiplier, lower it a bit, then start upping the multiplier until you find the sweet spot. Then it's just fine tuning.

Set your memory timings a bit loose while your messing. Voltages are just trial and error, but don't go too high.

EDIT: oh yeah. While you're upping the FSB make sure the RAM doesn't go over 800MHZ. You can set this after you've found the right FSB setting by altering the FSB-RAM ratio.

[sytaylor]

I r thmart!

[grey_1]

I r thmart!
Don't make me resurrect your "IDE cable" thread. :cool:











j/k :p

[Zapablast05]

^ What Sy said.

Find your highest FSB with a low multiplier, lower it a bit, then start upping the multiplier until you find the sweet spot. Then it's just fine tuning.

Set your memory timings a bit loose while your messing. Voltages are just trial and error, but don't go too high.

EDIT: oh yeah. While you're upping the FSB make sure the RAM doesn't go over 800MHZ. You can set this after you've found the right FSB setting by altering the FSB-RAM ratio.

I don't have a FSB:RAM ratio, it's all linked. Unless the FSB:RAM ratio is something else in the BIOS? I stopped with my CPU at 292MHz @ 11x, RAM @ 355MHz and no BSOD's or errors.

So basically, I can have my multiplier at 5x and my CPU FSB at like 600MHz?

[sytaylor]

Don't make me resurrect your "IDE cable" thread. :cool:











j/k :p

Everyone gotta learn sometime... :eek:

[Madpistol]

I have one small question... why don't we want the ram to go over 800mhz?

[ikjadoon]

I have one small question... why don't we want the ram to go over 800mhz?

No reason in particular, but that most memory is rated for 800MHz and higher might be unstable. You could just up the voltage, of course, or loosen the timings.

One thing to note, OP: linked (1:1) FSB has been known to dramatically increase memory bandwidth. My RAM, for example, actually runs below spec at 770MHz but that keeps the 1:1 and is actually faster than if I was running it at some weird divider, but over 800MHz. Any real-world increase? I have no freaking idea. Unlinked, however, will make your life much easier at a slight performance loss because it should automatically set a ratio to best suit your RAM.

Weird thing in computers, especially Intel's. Other weird quirks: 2 sticks run fine at 800MHz, but will only run at 750MHz with four sticks; quad-cores hit lower FSBs (and not for cooling issues); FSB holes/strap where the FSB just will not work at a certain speed: like 450-455MHz will never work, but 449MHz and 456MHz will work perfectly. FSB strap is where it jumps to the next standard: 266MHz to about 350MHz is the standard 1066MHz strap, i.e. will be very unstable at 350MHz. 351MHz-425MHz is the standard 1333MHz strap, i.e. 351MHz will be perfectly stable. I pulled those numbers out of my a$$, but they should be pretty close.

I hate to go off-topic, but I've had a question nagging me for MONTHS:

Which actually increases the heat of the processor? Voltage or speed??

~Ibrahim~

[LORD-eX-Bu]

voltage.

[Zapablast05]

It's something like 26F for every square MM on a processor times the voltage. It's some weird calculation on how the heat is calculated.

I didn't quite get that RAM speed thing, but I OC'd my RAM to DDR2 1066, and no issues.

[LORD-eX-Bu]

difference between 1066 and 800 mhz is negligible, you will have better results with tighter timings on a 1:1 ratio.

[Revs]

The main reason I said don't go over 800Mhz on the RAM is so you know it's not the RAM that's stopping you OC any higher. If you allowed your RAM to go up over 800Mhz while you upping the FSB and you hit a limit, it may be the RAMs limit and not the FSB. Keeping the RAM speed low would get round that.

[Zapablast05]

The main reason I said don't go over 800Mhz on the RAM is so you know it's not the RAM that's stopping you OC any higher. If you allowed your RAM to go up over 800Mhz while you upping the FSB and you hit a limit, it may be the RAMs limit and not the FSB. Keeping the RAM speed low would get round that.


Oh ok, well I lowered my RAM to run at DDR2 533, but it's OC'd at 400MHz and my FSB is at 320MHz @ 10x multi. So far I haven't hit a wall at all.

[mythy]

9X 378fsb -VS- 8X 425fsb = no difference :p

[Zapablast05]

9X 378fsb -VS- 8X 425fsb = no difference :p


Well duh, lol. So having a uber fast FSB doesn't matter?

[ikjadoon]

Well duh, lol. So having a uber fast FSB doesn't matter?

AFAIK, a higher FSB only equals higher memory bandwidth (if on a 1:1 ratio). If the RAM is the same on low FSB/high FSB (same total clock speed on CPU), there would no performance increase. I think.

~Ibrahim~

[Absolution]

AFAIK, a higher FSB only equals higher memory bandwidth (if on a 1:1 ratio). If the RAM is the same on low FSB/high FSB (same total clock speed on CPU), there would no performance increase. I think.

~Ibrahim~
higher memory bandwidth and looser timings has shown to decrease performance in some situations

hardly any applications even come close to using all the bandwith, keep the timings tight

and higher FSB = higher stress on the system all around, with a negligible performance increase, not worth the increase