Overclocking FSB vs Multiplier

[Krux]

no actually they don't both my gigabyte and my soyo dragon run the Kt400 chipset

 

[Taurus]

but all kt400 boards should support 333fsb processors..?

 

[Krux]

yes but they don't all have dividers some board can keep the clock speeds of the main bus seperate from that of the AGP and PCI some can not. so if you up the bus speed past 333 you start to not only over clock your cpu but your video card and your sound card and whatever else you may have plug into your board.

 

[Taurus]

right. but you said you couldn't get a 266 to run at 333 on your board.

eh.. nevermind. off to work.

 

[Krux]

I can't on my giga byte board if the cpu only supports a FSB of 266 pushing the FSB to 333 would make the AGP and PCI speeds way to high and thats bad not if my GB had a divider then I could push it to 333.

Now if I put a cpu in there like I have now that supports 333FSB then its fine because its running how it should be and I wouldn't be overclocking anything. IE; I put the new cpu in and the bus speed defaults to 166x2=333(332) and the agp and pci default to 33(pci) and 66(agp) as soon as I start messing with the FSB and push it past 166x2 IE; 170x2=340 the pci and agp also rise (this is a bad thing) and if they get to high they can cause damage to anything plugged into those spots.

now if I had the soyo board there are diff dividers so say I had a 333 CPU and I push it to 400FSB there are options like 1/2 and 1/3 and 1/6 which will push the AGP and the PCI speeds to one half or one third or one sixth of the main bus speed so at 400FSB you would use the 1/6th divider and your agp and pci will be at 66 and 33 instead of 110 and 67 (which is prolly an exageration but you get me)

 

[silky62678]

I know my board is able to lock the AGP, PCI slot. But DANG, i cant find where it is in the BIOS. Can someone with the same board help a brotha out?

 

[Taurus]

Originally posted by silky62678
I know my board is able to lock the AGP, PCI slot. But DANG, i cant find where it is in the BIOS. Can someone with the same board help a brotha out?

you can increase your fsb and your agp and pci frequencies will automatically stay put. you can manually change the agp frequency in one of the menus. i think the pci slots are changed with this too...? anyone know? if the pci slot freq is independent from the agp freq setting (not 1/2), then are the pci slots always 33mhz?

 

[jumpy]

Yep, there should be a setting like pci/agp and it should be set to auto. The agp frequency is always twice the pci frequency, so 33/66 or 35/70 etc. Therefore pci and agp frequencys will both go up when overclocking via the fsb if the board doesn't have frequency locking features, but you can use higher dividers to put them in spec again.

 

[Taurus]

so, just to clarify, if a board has an "agp frequency", and i set it to, say, 76mhz... will all my pci slots be running at 38mhz? if this was the case, wouldn't they call it "apg/pci frequency" to avoid confusion?

 

[Dublex]

Its worth pointing out again that you really, really, need to be very careful when playing about with overclocking .. I would reccommend making slight increments to make sure your system can cope with the extra juice - people in the past have "frankenstiened" their system - thrown the multiplyer like a switch too high like flicking an electricity beaker - and blown their system

Most people I'm sure know this, but its useful to have a reminder every now and again.

 

[jumpy]

Originally posted by taurus
so, just to clarify, if a board has an "agp frequency", and i set it to, say, 76mhz... will all my pci slots be running at 38mhz? if this was the case, wouldn't they call it "apg/pci frequency" to avoid confusion?

Yep. 38mhz should be fine, i've run at 80/40mhz on my other computer before without any problems, but it depends on your hardware (also remember hard drive bus frequencies are also increased )

It is called agp/pci frequency on a lot of boards...Just depends on the manufacturer.

 

[jumpy]

Good advice Dublex. Also do a fair bit of reading on the subject, as with anything, it helps greatly. Generally if you keep an eye on your temps and don't push the voltage too high, frying your system is pretty hard if you take small steps...