I just tried:

  mount -t cd9660 /dev/cd0c /cdrom

today, on a device that probes as:

  cd0 at scsibus0 target 6 lun 0: <TOSHIBA, CD-ROM XM-3301TA, 0272> SCSI2 5/cdrom removable

and got this:

  Mar  4 19:11:39 bullers /netbsd: cd0(esp0:6:0):  Check Condition on CDB: 0x43 00 00 00 00 00 00 00 0c 40
  Mar  4 19:11:39 bullers /netbsd:     SENSE KEY:  Illegal Request
  Mar  4 19:11:39 bullers /netbsd:      ASC/ASCQ:  Illegal Field in CDB
  Mar  4 19:11:39 bullers /netbsd:          SKSV:  Error in CDB, Offset 9, bit 6
  Mar  4 19:11:39 bullers /netbsd: 

on this system (a CVS update was done shortly before the build):

  NetBSD bullers.net 1.5.1_ALPHA NetBSD 1.5.1_ALPHA (BULLBALL) #0: Fri Jan 19 23:16:33 PST 2001     jon@bullers.net:/usr/src/sys/arch/sparc/compile/BULLBALL sparc

The disk did mount and seems to work fine.  But I don't ever remember
seeing this message coming out of the driver before...  (Unless I
tried to rip an audio track or something with this antique.)

Has it always done this and I just never noticed, or did the quirk
table get altered, or might there need to be a new quirk added to
the driver?

Jon