PDP-11 disk image question

Charles Anthony charles.unix.pro at gmail.com
Sat Feb 16 21:17:17 CST 2019

On Sat, Feb 16, 2019 at 10:53 AM Charles Anthony <charles.unix.pro at gmail.com>

> On Sat, Feb 16, 2019 at 10:04 AM Bill Gunshannon via cctalk <
> cctalk at classiccmp.org> wrote:
>> 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?
> My wild speculation would be disk geometry. I don't know the specific
> geometry of the RA81 disk, but it is possible that SIMH is writing a sparse
> disk image.
Did some reading up on the RA81 and looked at the relevant SIMH code; it
looks like the MSCP protocol is using Logical Block Addressing, which would
tend to disprove my sparse disk speculation.

-- Charles

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