ahc is not exactly the happiest camper sometimes yet on alpha:

scsibus1: waiting 2 seconds for devices to settle...
probe(ahc0:0:6:0): SCB 70 - timed out in Data-in phase, SEQADDR == 0x113
SCSIRATE == 0x6f
probe(ahc0:0:6:0): BDR message in message buffer
probe(ahc0:0:6:0): SCB 70 - timed out in Data-in phase, SEQADDR == 0x112
SCSIRATE == 0x6f
probe(ahc0:0:6:0): no longer in timeout, status = 2
ahc0: Issued Channel A Bus Reset. 1 SCBs aborted
cd0 at scsibus1 target 6 lun 0: <TOSHIBA, CD-ROM XM-3601TA, 0725> SCSI2
5/cdrom removable
cd0: sync (236.0ns offset 15), 8-bit (4.237MB/s) transfers