How the...?

[Codinerx]

Here is what I am struggling to understand: When people get huge overclocks using the fsb, how the heck do they prevent damage to their agp card and pci components? It just doesn't make any sense to me! I want to attempt a huge overclock using the fsb, but I am much to paranoid about ruining a hard drive or other component that I have not done so. Any enlightenment is greatly appreciated!!!
Joseph

 

[LtBlue14]

there are dividers that keep you from running the PCI/AGP slots from running at super high speeds. some motherboards will let you keep the slots at a constant speed (lock them)
others will give you PCI slots at 33Mhz @fsb100, and then the PCI speeds will rise up to maybe 42Mhz as you increase the FSB until 133, where it goes back down to 33. this can happen at 100, 133, 166, 200(?)
anyhow, the dividers are your answer
it's certainly possible that they don't exist on your motherboard, if you're finding that no matter how high you set the fsb your pci slots keep increasing

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[svol]

AGP cards should be able to run at AGP bus speeds of 89MHz (66Mhz default) with no problems.
Most PCI devices including IDE drives can handle a PCI bus up to 40MHz... which is a 7MHz increase.

A motherboard uses dividers to lower the FSB to the specific PCI and AGP clock speeds.
With 100MHz FSB you got a 1/3 PCI and a 2/3 AGP divider
With 133MHz 1/4 and 1/2
With 166MHz 1/5 and 2/5
And some motherboards can lock the PCI and AGP speeds so they don't increase when raising the FSB.

My PC eats so much money that I'm in 'desperate' need of it to buy PC3500 RAM, help Svol with his OC project!
--- PM me for information.

 

[Codinerx]

Hey man thanks for the help. One quick follow up question: How can I exceed the fsb overclock of 7mhz without damaging my pci stuff? According to your post, I would have to reach 166mhz in order for that other divider to kick in... what are your suggestions? Is there a way to force a divider or something? O by the way, its a soyo k7v dragon plus (266A) with an axp2000+ chip, and an ax-7 heatsink with a jet engine (vantec tornado) fan. Idle temps are around 32c, depending on the ambient, and load is around 36c. I doubt I can push it to 166, but what are your thoughts? Again, thanks a lot for the help!

 

[LtBlue14]

you can overclock the fsb more than 7mhz and the pci/agp slots will still be clocked fairly low
you can overclock from 133 to approx 160mhz and have a pci bus at 40 (40 = 1/4(fsb), fsb = 160, where 40 is the supposed max stable pci speed, and 1/4 is your divider between 133 and 166)
hopefully you'll be able to make the jump from 160 or 161 to 166, to cause less stress on your pci cards (and keep them working properly)
are you confident in increasing the voltage on your vcore? you'll probably need it to get there
i hope that post was clear

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[Codinerx]

Heheh great man, thanks for the help. I forgot that the dividers would be dividing any increases that I made to the fsb hehe. I'll definitly attempt that jump to 166... you think I can make it with an aircooler? Let me ask you this- is increasing the fsb, when applied only to the processor, the same as if I had unlocked the multiplier? Thanks for the great info!

 

[vince_b]

the asus P4PE locks the the pci/agp to 33/66

 

[svol]

Well your board oonly got a 1/4 and 1/3 PCI divider (not a KT333 or higher).
Depending on your CPU you will be able to run it at 166MHz FSB... you might need some better Northbridge cooling too if it is only a passive cooler.
If your computer doesn't run stable at 166MHz FSB increase the VCore or I/O Voltage (PCI Voltage) a little to see if that helps. If you only got PC2100 memory you probably also need to increase the DDR RAM voltage.

A FSB of 166MHz will not only make your CPU run faster but also will boost your memory, PCI cards and AGP cards.

My PC eats so much money that I'm in 'desperate' need of it to buy PC3500 RAM, help Svol with his OC project!
--- PM me for information.