aac0: COMMAND 0xffffffffxxxxxxxx TIMEOUT AFTER xx SECONDS

I've been receiving this message quite a lot lately if I put my Adaptec 
2410SA aac controller under really heavy load.  A quick look at the 
archives suggests that it used to be a problem a couple of years ago, but 
was apparently fixed.  Personally I've had no bother with it until a few 
months ago when I upgraded my version of -CURRENT, at which point it 
started misbehaving.

The process which seems pretty much guaranteed to cause it aggravation is 
Hercules, when I use it to IPL VM/370 the aac filesystems hang (and it 
eventually brings down ahc and fxp too, with complaints that "interrupts 
may not be functioning") and stays there until I kill off the process or 
press the reset button.

Any ideas what might've changed to make this problem resurface?

I'm also wondering if I might not be better off actually replacing the 
card with something better, or at least something better suited to 
FreeBSD: with the discs' and controller's write-caching turned off, the 
2410SA is s-l-o-w, about 6MB/s for contiguous writes to an array (either 
RAID-5 or RAID-10) (benchmarked using the admittedly somewhat crude "dd 
various block sizes to/from a /dev entry" technique), although reads are 
acceptable at ~50-60MB/s, if not especially earth-shattering.  Any 
suggestions (for something inexpensive!  If money were no object I'd've 
gone for a SCSI-only system), or might I just as well stick with the 
2410SA?

Cheers,

Chris.