on a sparc5:

	7 sparc5:~ # uname -a
	NetBSD sparc5 1.5T NetBSD 1.5T (CHUQ) #123: Fri Mar 23 04:18:18 PST 2001     chs@spathi.chuq.com:/home/chs/netbsd/src/sys/arch/sparc/compile/CHUQ sparc
	8 sparc5:~ # time pt -w -c 8000 -s 65536 /dev/rsd0g
	524288000 bytes transferred in 117.615 secs (4457647 bytes/sec)
	0.070u 35.916s 1:57.69 30.5%    0+0k 0+1io 0pf+0w



	1 sparc5:~ # uname -a
	NetBSD sparc5 1.5V NetBSD 1.5V (CHUQ.perf) #9: Mon May 21 08:56:48 PDT 2001     chs@spathi.chuq.com:/home/chs/netbsd/src/sys/arch/sparc/compile/CHUQ.perf sparc
	2 sparc5:~ # time pt -w -c 8000 -s 65536 /dev/rsd0g
	524288000 bytes transferred in 174.965 secs (2996529 bytes/sec)
	0.050u 18.404s 2:55.00 10.5%    0+0k 0+1io 0pf+0w

Let's see...  TQ went in 2000/11/30.  I removed a bunch of DELAY()s
on 2000/12/20.  Those are before the problem began.

FAS support went in 2001/03/29.  thorpej_scsipi went in 2001/04/25.  
I suppose the cause is probably one or the other of those.

Can you try a pre-thorpej_scsipi kernel and see if it still has
the problem?

Eduardo