aic79xx+ASC39320A crash

[Bjarne Thomsen <bjarne.thomsen@get2net.dk>]

I have had this problem with an Adaptec ASC-39320A for more than 2 years
(using the x86_64 version of the aic79xx driver).
The 39320A board has been tried on the Tyan 2882 and 2885 MBs with
the same result: I can copy a few small files, byt when I try to
copy a directory tree with a few hundred MB the system freezes
without any traces in the syslog or on the screen.
Two older Ultra 160 Adaptec boards work fine with the 2 Tyan MBs.
The raid option has been disabled for the ASC-39320A.

Tho years ago I gave up, but I have now tested the board
with some newer linux distributions using the Tyan 2885 MB
with the latest available BIOS (for both 2885 and 39320A):
ubuntu 6.06 LTS x86_64 (2.6.15 kernel)
Mandriva 2007 x86_64 (2.6.17 and 2.6.19 kernels)
Fedora core 6 (2.6.18 kernel)

The symptom is the same: the system freezes during the copy
of files from an IDE harddisk to a SCSI disk on the 39320 controller.
I am about to give up, again.

Any advice is welcome.

 -- Bjarne