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Increasing AGP Bus Speed?
- Thread starter jamesrb
- Start date
overclocking the agp bus by about 4MHz is enough to cause the videocard to have problems (windows crash due to video driver).
that's my experience anyway.
one would always want to lock the agp clock down, but even this is not possible (not precise enough) on motherboards with lock enabled.
i don't think many motherboards are physically capable of actually locking the agp/pci clock, since it is run off the same clock ic that the fsb uses. probably just uses some software trick which is inaccurate (4MHz agp increase with 32MHz fsb increase on my p4p800 which is already not stable enough to run games). if the agp was properly locked down, i could oc the cpu more.
if anyone knows the reason for the 'agp lock fallacy' i'd like to hear about it.
that's my experience anyway.
one would always want to lock the agp clock down, but even this is not possible (not precise enough) on motherboards with lock enabled.
i don't think many motherboards are physically capable of actually locking the agp/pci clock, since it is run off the same clock ic that the fsb uses. probably just uses some software trick which is inaccurate (4MHz agp increase with 32MHz fsb increase on my p4p800 which is already not stable enough to run games). if the agp was properly locked down, i could oc the cpu more.
if anyone knows the reason for the 'agp lock fallacy' i'd like to hear about it.
morningreis
[H]ard|Gawd
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It really provides no advantage.
PliotronX
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In fact, some have found better performance running at 50MHz 
I've heard overclocking the AGP bus can cause higher GPU temps, but I have not measured. The highest my 9700 will go before problems arise is about 74-76MHz. I have observed that my GPU clock can be limited if the AGP bus is overclocked that high so higher temps would make sense, at least in this case.
I've heard overclocking the AGP bus can cause higher GPU temps, but I have not measured. The highest my 9700 will go before problems arise is about 74-76MHz. I have observed that my GPU clock can be limited if the AGP bus is overclocked that high so higher temps would make sense, at least in this case.hfc said:
That's not true. The NV chipsets have generated the AGP/PCI bus clocks separate of the FSB clock generator since NF2. However, the AGP and PCI bus clocks are generated from the same source, so while it is possible to up the FSB and not affect the AGP/PCI bus clocks, raising the AGP bus clock will take the PCI bus along with it.
Un4given said:
Thats what I thought was the case, that AGP and PCI are together, but seperate from the FSB.
With the NF2, that was a BIG feature to have, to be able to crank up the FSB, but not to overclock the AGP. I thought it was a feature that was supposed to be on the NF1 boards also, but I may be wrong.
hfc said:
I've not used an Intel CPU since my P3, so I'm not that up to date on the offerings of the Intel chipsets. I do know that VIA tried to get such a FSB lock to work in one of their early Athlon chipsets and it didn't work right, but NV's has worked properly since the NF2. However, you are correct in that the mobo maker must properly implement that feature for it to work as well.
In fact, my model of MSI board was one that was known to have an issue with the lock unless you changed the AGP bus from 66MHz to 67MHz. They fixed this in a later BIOS release, but it's not a fool proof technology if not implemented properly.