Seems to reset DMA on drives ok:

hdparm -d1 -X mdma2 /dev/hdl

FreeBSD notes:


Controllers:

argus-n1 onboard SATA:
 - Seems to get occasional errors discovered by md5 check.

Promise SX4:
 - Seems to work great
 
HighPoint
 - Seems to work ok.  Does not move bits very fast and shows up as UDMA100.
 
Promise 133TX2:
 - Might have been getting silent errors with WDC 250's on n1
 