Bug 31736

When booting FreeBSD the following error came up. It looks like there is an error with writing in DMA mode to my harddisk and after a few retries it is switching from DMA to PIO mode. My harddisk is 100% correct and supports DMA33/66 and my motherbord with SiS 5591 chipset works fine, also the cable is correct (more cables allready tried). Under linux everything is working fine...
(when I go on and ignore the error it looks like my system becomes unstable)
dmesg:

ad1: 16479MB <Maxtor 91728D8> [33483/16/63] at ata0-slave UDMA33
acd0: CDROM <CD-ROM 40X/AKU> at ata1-slave using PIO4
Mounting root from ufs:/dev/ad1s1a
ad1: WRITE command timeout tag=0 serv=0 - resetting
ata0: resetting devices .. done
ad1: WRITE command timeout tag=0 serv=0 - resetting
ata0: resetting devices .. done
ad1: WRITE command timeout tag=0 serv=0 - resetting
ata0: resetting devices .. done
ad1: WRITE command timeout tag=0 serv=0 - resetting
ad1: trying fallback to PIO mode
ata0: resetting devices .. done

Fix: 

There is a little solution to call sysctl before mounting the harddisk and give it the command to setting dma to pio mode, but pio mode is much slower then DMA mode, about 9 mb/s with linux... If it's possible I want to run in DMA mode offcourse :)
How-To-Repeat: Everytime on booting the problem exist...