100% cpu usage during ANY disk activity

[chareos]

nForce4 MB
AMD ATHLON64 3000+ CPU
Kernel: 2.6.18, tried Vanilla and Kolivas patched
1x HDD EIDE (32bit bus, DMA on, UDMA5 mode).
1x HDD SATA
(both hard drives give same problems)

Hi guys,

I'm facing a strange problem, which degrades system-wide performances on my box.

Any disk operation I issue (file copy, dir listing, etc) my CPU usage jumps up to 100%.

This problem appears so CPU related that if I disable powernowd (CPU stays up to 1800MHz then) copy speed goes up to 19MB/s (from 14MB/s it stays when CPU works at 1GHz).


In kernel options I enabled (kernel built-in, no modules):
ATA support ->
Enhanced IDE ->
PCI IDE ->
Generic PCI Bus Master ->
- USE PCI DMA by default when available
- AMD and nVidia IDE support

Looking around on internet I think my transfer rate speeds are perfectly fine on both my IDE and SATA drives.
My only problem is CPU usage, completely mad.

I tried also to reboot with noacpi noapic kernel parameters, no improvement.



Thanks for any suggestions !