>I also loaded FreeBSD 3.1 on the system as a test;  it seems to work OK.
>Not to disparage FreeBSD, NetBSD's what I've got on all my other systems,
>and by gum, I'd like it here!   So, the hardware itself seems OK.  Just
>in case it triggers anything for anyone, here's what a FreeBSD kernel
>with AHC_DEBUG says (though I had to edit some stuff out, as it didn't
>compile cleanly with AHC_DEBUG):

Booting with -v would be more useful.  I haven't used the AHC_DEBUG
stuff in a long time.

>ahc0: <Adaptec aic7880 Ultra SCSI adapter> rev 0x00 int a irq 11 on pci0.11.0
>ahc0: aic7880 Wide Channel A, SCSI Id=7, 16/255 SCBs
					  ^^<= That's the important number.			
>So, anyway, I'm at the point now where I'm slowly sifting through the 
>attachment of the ahc device using GDB, but I'm afraid my skills might
>not be up to the task.  Anyone got any further pointers of what I might
>look at?

Look at the loop in ahc_init that determines the number of hardware
SCBs.  You should also see if NetBSD is preferring memory mapped I/O
over PIO as FreeBSD defaults to PIO access of the chip.

--
Justin