PCI bus frequency tolerance?

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[H]ard|Gawd
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Jul 25, 2005
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Since my motherboard lacks a PCI bus lock (although strangely enough, it has an AGP lock), what is a reasonable range for the PCI bus frequency. For example, how high can the PCI bus frequency go before I begin seeing hard drive issues?

I'm running an nForce 250 chipset and from what I've been reading it does have a PCI bus lock, although I don't see an option for it in the bios. And ClockGen seems to show an increase in my PCI bus freq when I raise the FSB (but AGP bus speed remains constant)...
 
I've seen it even as soon as 36MHz but that was on a really flaky motherboard to start with. Generally you've got a LITTLE bit of wiggle room, but IDE hard drives can easily be effected by unstable PCI clocks and cause big trouble so take it slow.
 
The AGP lock should lock the PCI bus as well.

Be sure that its clockgen you are using.
I found the clocking tools from Gigabyte did what you describe - despite locking the AGP bus, the clocking tool ignored it and changed the PCI speed.
Clockgen woked as expected and left the AGP/PCI speed alone when locked..
 
So you're saying that although ClockGen shows the PCI bus speed changing, the PCI bus speed actually remained the same?
 
Are you 100% sure that the AGP/PCI bus is locked?
Depending on the BIOS, you have to do different things.
On mine I had to set the AGP speed to 67.
(I also had to hit a strange key combo in the CMOS to get one of the overclocking pages to appear)
From what you have said it looks like you did find the lock setting but best to be sure.

When using the Gigabyte tool I saw the behaviour you are getting.
Using clockgen, when the FSB is moved, the PCI/AGP clock remains unchanged.
Its possible that I' used a different version of clockgen so you might want to try V1.04 for NForce 3

btw the PCI and AGP speeds are tied together.
If you change the AGP speed 10MHz, the PCI speed will change 5MHz
If you are seeing one change without the other, either none of them are changing or both are.

ps for reference, my mobo was the Gigabyte K8NS Ultra.
 
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