| ahc1 at pci0 dev 6 function 0
| ahc1: interrupting at irq 9
| ahc1: aic7880 Wide Channel A, SCSI Id=7, 16/255 SCBs
| scsibus1 at ahc1 channel 0: 16 targets, 8 luns per target
| [...]
| ahc1: target 4 using 8bit transfers
| probe(ahc1:4:0): SCB 1d - timed out in Command phase, SEQADDR == 0x155
| SCSIRATE == 0x0
| probe(ahc1:4:0): BDR message in message buffer
| probe(ahc1:4:0): SCB 1d - timed out in Command phase, SEQADDR == 0x155
| SCSIRATE == 0x0
| probe(ahc1:4:0): no longer in timeout, status = 0
| ahc1: Issued Channel A Bus Reset. 1 SCBs aborted
| 
| Does this ring any bells?  The drive is alone on that SCSI bus, btw.

  Indeed it does. My oldish CD-Rom started doing that since the new
ahc driver, like this:

| ahc0: target 4 synchronous at 4.0MHz, offset = 0xf
| ahc0: target 4 synchronous at 4.0MHz, offset = 0xf
| ahc0: target 4 synchronous at 4.0MHz, offset = 0xf
| ahc0: target 4 using asynchronous transfers
| probe(ahc0:4:0): SCB 1d - timed out in Data-in phase, SEQADDR == 0x112
| SCSIRATE == 0x0
| probe(ahc0:4:0): BDR message in message buffer
| probe(ahc0:4:0): SCB 1d - timed out in Data-in phase, SEQADDR == 0x113
| SCSIRATE == 0x0
| probe(ahc0:4:0): no longer in timeout, status = 2
| ahc0: Issued Channel A Bus Reset. 1 SCBs aborted
| ahc0: target 4 synchronous at 4.0MHz, offset = 0xf
| ahc0: target 4 synchronous at 4.0MHz, offset = 0xf
| ahc0: target 4 synchronous at 4.0MHz, offset = 0xf
| ahc0: target 4 using asynchronous transfers
| scsibus0 target 4 lun 0: <, , > SCSI0 0/direct fixed not configured

  What cured it for me as a work-around was to turn "use wide
transfers" (or whatever the wording is) off for that particular
target in the adaptec's bios. You could also try to fiddle with
the "transfer rate" setting while you are there.

	mjl