poor ATA disk speed with ICH2

Hello,

first time I installed a beta of FreeBSD 5.3 I noticed very poor disk speed.
I built a kernel without this whole debugging stuff; but it remains bad. I
supposed that this issue depends on further debugging features which I
didn't know. So I waited until UPDATING told that debugging options are
removed from kernel and userland. Now I built a new kernel again and the
disk speed is still unacceptable. Is there any further debugging option?

Some facts:

FreeBSD 5.3-BETA3 without any debugging:
	per char write: 13.78 MB/s (32.7% CPU usage)
	block write: 13.97 MB/s (12.8%)
	per char read: 22.31 MB/s (45.2%)
	block read: 37.44 MB/s (14.8%)

FreeBSD 4.10-STABLE:
	per char write: 37.29 MB/s (75.7%)
	block write: 36.91 MB/s (28.7%)
	per char read: 38.53 MB/s (80.4%)
	block read: 37.45 MB/s (10.9%)

(tested with bonnie, atacontrol shows UDMA100 both)

Controller: Intel 82801BA (ICH2)
Hard disk: Seagate ST380021A

Best Regards
Björn König