PDP-11 disk image question

Jerry Weiss jsw at ieee.org
Sat Feb 16 11:58:26 CST 2019

On 2/16/19 7:55 AM, Bill Gunshannon via cctalk wrote:
> So, I used SIMH to do an install of a complete OS on
> an RA81 disk.  I would like to  move this to a real disk
> and try it on a real PDP-11.  Is there a way to do this
> using dd on a BSD machine?  I tried but it created a
> non bootable system.  Well, actually, it starts to boot
> but then fails very early in the startup process.  I used
> "dd if=filename of=raw-device bs=1024".  Could it be that
> the block size needs to be something else?
> I know that VTServer and PDPGUI can move disk images but
> it would take a week at 9600 baud and I think very little
> likelihood of it ever completing successfully.
> bill
As long as the media is presented as "Error Free", you should be able to 
to change the block size.   Since a RA81 (MSCP) remaps error blocks 
automatically and invisibly, it should work.  Is the media type the same 
on SIMH and Real PDP11?   If all else fails try bs=512.

For drives that have OS visible media defects, you should make sure the 
block size matches the same on the media and also use the option 
"conv=noerror,sync".  Otherwise dd will actually reorders the blocks(!), 
good first then zero fill the ones it cannot read.


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