Overclocking FSB vs Multiplier

S

silky62678

Guest
#1
When overclocking what is the difference if any, when changing the FSB vs changing the Multiplier?
 
#2
CPU Clock speed = FSB x multiplier

The multiplier is usually locked, so most people overclock by increasing the speed of the FSB. The difference is that when you change the FSB speed, the speed of your RAM and your PCI bus changes as well. Changing the multiplier, on the other hand, affects only the CPU clock speed.
 

Taurus

hardware monkey
#6
Originally posted by silky62678
Oh ok, I changed the Multiplier in the bios to 8*15
what do you mean? your cpu has a multiplier of 15 by default (133x15=2000mhz). i'm not sure what 8*15 is. 120mhz? :confused:
 
R

RobbieSan

Guest
#7
lol.. it depends on your CPU.. my 2600+ (333fsb) defaults to 12.5x166 (2.08GHz)..

either way will work.. what you need to experiment with is stability.. sure, you can crank up the FSB or multiplier to achive xGHz but how stable is it at xGHz? you need to try different combinations but keep in mind taht as you increase the CPU speed you will most likely need to:

1. increase CPU voltage (vcore) to compensate for the increased energy requirements

2. better cooling - more speed means more hear means more cooling

3. memory timing and voltage - you will probably need to "relax" (slow down) memory timing and possibly increase mem voltage from 2.6 to maybe 2.7 or 2.8v

4. I/O cooling - the increased speeds may also require more cooling on the I/O (ie. Northbridge) chipset since it is running faster and hotter..

5. Ambient temp (case temp) - you may also need to add a couple of case fans to increase case airflow and reduce ambient temp
 

LeeJend

OSNN Veteran Addict
#8
Getting back to the original question...

When you increase the multiplier all you are aver clocking is the CPU.

If you change the FSB, depending on your motherboard, you may be overclocking your RAM, PCI slots, and/or AGP slot. Any one of these can turn into the stability limiter. If you can unlock the multiplier (or if it comes unlocked) overclocking is a lot easier. Note the newer "overclocking friendly" motherboards
have independent speed settings for each item.

And to answer the P4 question, nobody has been able to unlock the P4 multipliers yet.
 

Taurus

hardware monkey
#13
most 2600+'s have the 266fsb, actually.

anyway, i read a review of the 2400+ where they were able to push it to like 330fsb. you might have some luck overclocking.
 

Krux

Nissan Powered
#14
but if you up your FSB that high you have to drop your multiplier I got an 1800+ to 1.577 @ 333FSB was only a what 40mhz over clock but the performance was way higher.

when you up your FSB your get better performance then if you just up the miltiplier, but when you up your FSB you can damage your cards in your PCI and AGP slots along with the CPU if you just up the multiplier your only endangering the cpu.
 
#15
Originally posted by LeeJend
And to answer the P4 question, nobody has been able to unlock the P4 multipliers yet.
Well, either the second or third revision of my BIOS let me play with the multiplier. All the revisions since that (there has only been 2 or 3 since then) have it locked away. *shrug*
 
J

jumpy

Guest
#16
Originally posted by Eck
Well, either the second or third revision of my BIOS let me play with the multiplier. All the revisions since that (there has only been 2 or 3 since then) have it locked away. *shrug*
Yes, most bios' for P4 boards will let you play with the multiplier, but it doesn't mean it will change it. P4's are locked, and there's no way you're going to unlock it (unless you have an ES, or a chip fab in your house :p)
 
S

silky62678

Guest
#17
Originally posted by Krux
but if you up your FSB that high you have to drop your multiplier I got an 1800+ to 1.577 @ 333FSB was only a what 40mhz over clock but the performance was way higher.

when you up your FSB your get better performance then if you just up the miltiplier, but when you up your FSB you can damage your cards in your PCI and AGP slots along with the CPU if you just up the multiplier your only endangering the cpu.
When u up your FSB, what was your clock speed after uping (is that a word)the FSB?
 
J

jumpy

Guest
#18
Doesn't krux say 1.577ghz, which is 166x9.5... Is that what you mean? You won't have to worry about pci/agp speeds on that board though because it has a pci/agp lock as every good board should :) (just make sure its enabled in the bios).
 

Krux

Nissan Powered
#19
I did that on a soyo dragon platinum it has dividers that split the AGP and PCI off from the main bus speed. but if you have like a gigabyte board you couldn't do that because there are no dividers and if you had a 266 chip and pushed it to 333 your agp and pci would be at like 54-86 which is WAY out of spec (33-66) and could damage the cards in there slots.
 

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