Doing heavy disk activity (make build and other things) in a -current
kernel built today with "option AHC_TAGENABLE", the disk stopped responding.

The rest of the system was OK, including the "systat" :iostat I had
running in another window -- only disk accesses hanged.   However
the systat output showed occasional short bursts of disk activity
(I couldn't hear the disk doing anything though).

After a reboot, I found the following in my syslog output:

May 27 17:22:19 sean /netbsd: sd0(ahc0:0:0): Queue Full
May 27 17:22:19 sean /netbsd: ahc0: WARNING no command for scb 15 (cmdcmplt)
May 27 17:22:19 sean /netbsd: QOUTCNT == 0

fscking, btw, found entirely clean partitions except in the one
where an unlinked file had been open (with the usual fsck complaint).

Moreover, I found later entries in /var/log/messages, all from xntpd:

May 27 17:25:30 sean xntpd[210]: synchronized to 192.121.159.242, stratum=2
May 27 17:26:33 sean xntpd[210]: synchronized to 192.36.143.14, stratum=2
May 27 17:26:41 sean xntpd[210]: synchronized to 192.121.156.9, stratum=2
May 27 17:27:30 sean xntpd[210]: synchronized to 192.36.143.150, stratum=1
May 27 17:28:20 sean xntpd[210]: synchronized to 192.121.156.9, stratum=2
May 27 17:28:22 sean xntpd[210]: synchronized to 192.36.143.150, stratum=1
May 27 17:28:26 sean xntpd[210]: synchronized to 192.121.156.9, stratum=2
May 27 17:30:19 sean xntpd[210]: synchronized to 192.121.159.242, stratum=2
May 27 17:31:04 sean xntpd[210]: synchronized to 192.121.156.9, stratum=2
May 27 17:33:16 sean xntpd[210]: synchronized to 192.36.143.150, stratum=1
May 27 17:33:17 sean xntpd[210]: synchronized to 192.121.156.9, stratum=2
May 27 17:33:22 sean xntpd[210]: synchronized to 192.121.159.241, stratum=2
May 27 17:33:53 sean xntpd[210]: synchronized to 192.36.143.150, stratum=1
May 27 17:33:53 sean xntpd[210]: synchronized to 192.121.159.241, stratum=2
May 27 17:34:44 sean xntpd[210]: synchronized to 192.36.143.150, stratum=1
May 27 17:39:57 sean syslogd: restart


I'd love to keep using tagged queueing since it makes an enormous
difference.

This is the obviously relevant part of dmesg's output:

NetBSD 1.3E (EBONE) #2: Wed May 27 16:27:55 CEST 1998
...
pci0 at mainbus0 bus 0: configuration mode 1
...
ahc0 at pci0 dev 8 function 0
ahc0: interrupting at irq 11
ahc0: aic7880 Wide Channel, SCSI Id=7, 16 SCBs
scsibus0 at ahc0 channel 0: 16 targets
ahc0: target 0 using 16Bit transfers
ahc0: target 0 synchronous at 20.0MHz, offset = 0x8
ahc0: target 0 Tagged Queuing Device
sd0 at scsibus0 targ 0 lun 0: <QUANTUM, XP34550W, LXY4> SCSI2 0/direct fixed
sd0: 4341MB, 5899 cyl, 10 head, 150 sec, 512 bytes/sect x 8890760 sectors

	Sean.