PDP-11 disk image question

Bill Gunshannon bill.gunshannon at hotmail.com
Sat Feb 16 15:20:13 CST 2019

On 2/16/19 3:57 PM, Zane Healy wrote:
>> On Feb 16, 2019, at 10:04 AM, Bill Gunshannon via cctalk <cctalk at classiccmp.org> wrote:
>> OK, as usual, I hac caused confusion and didn't get my point across.
>> let's try with a detailed explanation of what I did that didn't seem
>> to work.
>> First, my hardware.  I  have a PDP-11/93 with a CMD SCSI Module and
>> a BA350 with 6 2GB hard drives.  The Module is set up to present RA81
>> disks and the first 3 disks have 4 partitions each which should work
>> out to 12 RA81 disks. (But that last part is unimportant right now!)
>> I used SIMH to build RSTS V9.6 on a simulated RA81 disk.  I wrote the
>> disk as a file to a CDR in CD9660 format.  I moved the BA350 and the
>> CD to a VS3100 running OpenBSD.  I was able to mount the CD under
>> OpenBSD and see the file containing the disk image.  I used dd with
>> the command given in my original message (and repeated above) to try
>> to write the image to a real SCSI disk.  When I try to boot it I get
>> the RSTS Message "INIT.SYS not found".  The disk was completely blank
>> to start so the RSTS info must have been copied but apparently not
>> copied correctly.
>> Any more suggestions?
> That’s a really nice setup.
> I’ve had a theory for a while now, but never had cause to actually put it to the test.  RSTS/E would probably be why I would put it to the test.
> First some background.  I’m far being skilled from RSTS/E, but I have managed to get RSTS/E 10.1 and DECnet/E installed and running on my PDP-11/73, on a SCSI drive.  While I’ve been able to install RT-11 and RSX-11M+ from CD-R, I wasn’t able to figure out how to do that with RSTS/E.  With RT-11 or RSX I boot from the CD-R, and do the install.  The next option I have is a TLZ06 drive, and I write the tapes with my Compaq XP1000/667 running OpenVMS.  As I recall, that worked fine for installing RSTS/E, but it wouldn’t work for DECnet/E, for DECnet/E I had to actually install from a TK50 tape.

I guess I don't understand where you are getting bootable CDROM install
media for any PDP-11 OS.  I am not aware of any PDP-11 that supported
CDROM as a boot device either.

> Now for the theory…  What if you do a ‘dd’ of the drive you want to install it to.  Then copy that image over to where you’re running SIMH, and use a copy as your disk image for SIMH.   Install RSTS/E, and write it back to the simulated RA81 using dd.  I do not know if this will work, but it’s something I’ve wanted to try for a long time.

Might be interesting to try.

> Another possibility is that you could be running into some sort of problem with the RA81 simulation with the controller.  Do you have the manual for the Controller?  If so what OS’s and versions does it say it supports?  Out of curiosity, which SCSI board are you using?  I didn’t realize this was a feature that the CMD controllers have.  Will it simulate any other drives?

I  have the manual.  I only chose RA81 as it was the biggest size
disk supported by all the PDP-11 OSes.  I would love to use bigger
but you have to pick one in the configuration of the controller.
You can choose to not emulate anything but I expect most PDP-11
OSes would have a problem installing to a very large, unspecified
type, disk.

I have a CQD=220A/MT configured for 6 disks and one tape.
As for disk types, you can toggle RA ON or OFF on each drive.
You can specify one RA type that will be in effect for any
disk with RA ON.  Types are: RA70, RA80, RA81, RA82, RA90 and RA92.
OSes supported are VMS, Ultrix, Unix/Berkeley, RSX-11M, RSX-11M-Plus,
RSTS/E, RT-11, DSM-11, ISM-11, TSX+, VAXELN and AT&T UNIX.
Most recent versions of all of them.  Or so it claims.  The only
OS I have ever had running on one of these cards was RT-11.  I
am just now getting around to trying to play with other OSes
to see if they actually work.  But, getting the OS onto the
machine is a challenge all in itself,


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