Safe PCI/AGP bus

[thelanx]

I've heard that overclocking your fsb without a PCI/AGP bus lock can cause data corruption in your hard drives? How does that happen? Or is that not because of PCI/AGP but because of system bus? So what is the highest PCI/AGP bus that is safe?

 

[Sahakiel]

Originally posted by: thelanx
I've heard that overclocking your fsb without a PCI/AGP bus lock can cause data corruption in your hard drives? How does that happen? Or is that not because of PCI/AGP but because of system bus? So what is the highest PCI/AGP bus that is safe?

In short, clock timings.

33MHz PCI 2.1, 66MHz for 66MHz PCI 2.2 cards, 133MHz for PCI-X.
66MHz AGP.

 

[Soulkeeper]

yeah if the pci bus starts going above the 35 to 37mhz range hard drives can start to corrupt
i had a quantumn fireball hard drive (aventually went out on me) that would corrupt a few mhz lower than my other hard drives would, so it's different for each hard drive, vid card, and other devices.

but generally speaking overclocking the pci bus does nothing for performance and really reduces stability each 1mhz above spec it goes.
When overclocking of the agp bus performance is also negligable in most cases, and usually not worth doing unless the agp bus is already being saturated or "maxed" out (which really isn't happening enough right now with current vid cards to yeild noticeable performance increases)
people have been know to get a nice agp overclock approaching 80mhz to 100mhz, but again even those numbers don't really help performance.

PCI/AGP locks are great for us overclockers because we don't have to worry about stability issues and risks of corruption. And overclocks are no longer limited by the few extra mhz extra you can push the pci bus at the highest divider the chipset/motherboard supports.
it's a good thing

 

[thelanx]

Well the reason I ask is because my mobo has asynchronous mode, but it doesn't seem to work, so my overclocking is limited by the pce/agp bus. How exactly does the hard drive get corrupted anyways, and does that mean you lost all your data on that drive?

 

[Soulkeeper]

Originally posted by: thelanx
Well the reason I ask is because my mobo has asynchronous mode, but it doesn't seem to work, so my overclocking is limited by the pce/agp bus. How exactly does the hard drive get corrupted anyways, and does that mean you lost all your data on that drive?

basically the ide controller runs off the pci bus at 33mhz (thus limiting max throughput to 133MB/s theoretical) as the pci bus increases so does the ide controller and thus i suppose the ata100, ata133, etc transfers between the drive and rest of the system.

so basically you end up overclocking something that was never designed to overclock or run faster than what it was made to run at.
sometimes the system might just give you a BSOD or just reboot\
but the worst case senario (besides actually damaging the hardware itself) would be corrupting the filesystem (or just one or more files), causing you to have to reinstall your OS and software again.

 

[thelanx]

Wow sounds pretty bad, data loss isn't exactly a thing I wanna risk. Hmm, if only this asynchronous thing works for my motherboard.