aci79xx driver problem

[Juris Krumins]

I have a new server with Adaptec SCSI chip 7901 with Ultra 320 support.
I'v installed FreeBSD 5.1 on that server, but I have problems with SCSI
system.
If I stay default (Ultra 320 mode with Packetized mode on ) then I have
kernel panic or different erros from ahd driver.
If I change mode (Ultra160 with Packetized mode on ) I also have lots of
errors for example when copy big directory
If I change mode (Ultra160 with Packetized mode off ) I have all working
correctly and no errors.

So i wonder are there any ways to force SCSI subsysten work correctly in
Ultra 320 mode. The Packetized mode in Ultra320 mode is necessery that's why
I can't turn it off.

Hardware:
MB Intel SE7501BR2
Adaptec aic7901 chip
Maxtor ATLAS10K4_36WLS scsi disk

Any ideas ?
Any answer would be apreciated.