1/6, 1/4, 1/3 PCI divider. Can anybody explain?

[lorinser75]

Hello guys.

I am a newbie in overclocking, and just about to start learning it.
I think I've already grasped the concept about FSB, multiplier, & core voltage.

But, I am still confused about the term PCI divider, 1/6, 1/4 or 1/3 etc. Can anybody patiently explain to me this term?
Does that have anything to do with AGP/PCI lock?

thanks guys

 

[Duvie]

Dividers were used more so prior to the agp/pci locks of the newer boards.....

The dividers were used to at certain fsb get the pci clock back into spec of 33mhz and agp to 66mhz....Boards may have had multiple dividers because they supported many cpus that may have had diff. system buses...Ie like the tbird 200fsb and 266fsb....

At 100fsb the board would employ a 1/3 divider to keep the pci at 33mhz...problem before locks was that as you raised the fsb during ocing to say 110fsb that the pci went up with that ratio to a 36.67mhz...seems little but some harddrives and devices are very sensitive to this change and could result in instability. once you got to 120fsb or 40mhz pci many harddrives may result in corrupted data or even physical damage....For the lucky ocers who could get to 133fsb then the board would magically (not really) switch to a 1/4 divider and put the pci back to 33mhz....Each mhz of fsb above that ran against that 1/4 divider....As we got into the palomino line there were many boards implementing a 1/5 divider making 166fsb the next safe haven for the pci....so taking that info it is obvious a 1/6 divider works with 200+fsb chips or fsb ocing.....

Locks are the best as there is really no definitiveway to tell what device is going to be ultra sensitive to pci being out of spec even the slightest...The lock takes that out of the equation....

If you don't oc you likely don't run into these issues and the boards bios autmatically detects which divider is needed with your rated fsb chip to keep pci in spec as default...

 

[lorinser75]

Thanks a lot Duvie.

It's all very clear now.
I really really appreciate you taking your time to write that Duvie