PDP-11 disk image question

Bill Gunshannon bill.gunshannon at hotmail.com
Tue Feb 19 07:39:10 CST 2019

On 2/18/19 10:59 PM, Glen Slick via cctalk wrote:
> On Mon, Feb 18, 2019 at 5:18 PM Bill Gunshannon via cctalk
> <cctalk at classiccmp.org> wrote:
>> Well, all I really have are CQD module which does MSCP and TMSCP
>> over SCSI.
> Do you have any SCSI tape drives? 

Sure.  I have a SCSI 9-track and a 1.4" QIC  (TKZ-10) and even a
SCSI TK50 if I ever get it fixed (but then we know how likely it
is that any of the physical TK50 drives will actually work at this
point in time!!)  But all of these require TMSCP media and the only
one I have ever seen (and actually have in my possession) is TK50.

>                                    I have successfully installed RSTS/E
> 10.1 from install tapes on real PDP-11 hardware using an Exabyte
> EXB-8200 8mm tape drive attached to a CMD CQD-220/TM. The target hard
> drive for the installation was also attached to the CMD CQD-220/TM.
> That is always one route you could try.

Yes, if I could get a TMSCP Install Kit on a 9-track tape. :-)

> My guess is that the other posts about disk sizes being different is
> likely the issue. When I want to use a physical drive attached to
> Q-Bus SCSI controller to be the target of a copying a simulated disk,
> I usually try to verify that the MSCP block count for the physical
> drive is actually what I expect it to be.

I guess I was naive.  I used to work with real RA drives in the
past and figured the emulations were at least accurate enough to
know how big the disk was.  It wasn't a secret.

> If I can attach the Q-Bus SCSI controller and drive to a MicroVAX
> system I can boot VMS and mount /foreign the drive and show dev /full
> the drive to get the block count. Or if the the Q-Bus SCSI controller
> and drive are attached to an 11/53, /73, /83 (or /93 if I had one of
> those) I can boot the 2.11BSD install tape and run the standalone
> disklabel program to display the reported MSCP geometry of the drive.
> The must be several other ways to display the MSCP reported geometry
> of a drive, those are just two that I have used myself in the past.

All sounds like fun, but if the two emulations don't do RA81
correctly the information doesn't really do me much good.  I
certainly can't change the CQD's idea of what an RA81 is.

I am sure  once I successfully leap this hurdle the system will
run RSTS nicely (I only wish I had the CIS option for one of my
machines).  Like I said earlier, good thing this is only a


More information about the cctalk mailing list