PDP-11 disk image question

[Charles Anthony]

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

>
>
> 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