MSCP SCSI cdrom behavior

[Don North]

Zane H. Healy wrote:
> At 3:43 AM -0500 2/17/06, 9000 VAX wrote:
>> Greeting,
>>   May I ask how an MSCP SCSI controller behaves when a CDROM drive is
>> connected to it? When there is no CD in the drive, what does "show
>> dev" console command show? Can I take out the CD when an OS is
>> running? Can I take out the CD after I unmount it from the file
>> system?
>>
>>   My controller treats a CDROM drive as a read-only HD now. Please let
>> me know how other controllers deal with the CDROM drive. Thank you.
>
> Good question.  One thing to remember is that a lot of Q-Bus MSCP SCSI 
> controllers won't even talk to CD-ROM's, and if they will you have to 
> find one that will talk ot it.  I've had good luck with Plextor caddie 
> drives, and an RDD-42, but I've another drive that works fine on my 
> Alpha's that won't work with my Q-Bus controller.
>
> I only use my SCSI (Unibus or Q-Bus) on PDP-11's, so I don't have the 
> "SHOW DEV" option.  Having said that, as I recall, they show up as a 
> Read-Only HD.
>

I have an Emulex UC18 (dual SCSI, one channel setup for MSCP disk, other 
setup for TMSCP tape) on my PDP-11/44. I have both 2.1GB Seagate hard 
drives and DEC RRD43 (Toshiba) CDROMs on the disk port. I've used the 
CDROM to boot XXDP, RT-11, BSD2.11, and RSTS. The Emulex reads the CDROM 
and reports the size of the disk as the size of the drive. If no disk is 
present it reports drive offline. I can mount/unmount (BSD) and switch 
media in the CDROM at will.