[Simh] Reading PDP-15 and PDP-9 tapes

[Paul Koning]

> On Dec 20, 2018, at 7:40 PM, David Gesswein <djg at pdp8online.com> wrote:
> 
> On Wed, Dec 19, 2018 at 02:31:47PM +0100, Pontus Pihlgren wrote:
>> Hi
>> 
>> But it just seems to loop over DECtape I/O-instructions.
>> 
>> Any suggestions to what I should be doing?
>> 
> Reading the OS/8 handbook I think it is only intended to transfer files
> and doesn't support copying entire devices.

Doing that on PDP-11 would be straightforward, using the RALL (read all) DECtape controller command.  That's programmed I/O, not DMA.  The DECtape formatter uses that (or WALL, which uses the same programming approach).  I haven't seen any standard utilities that do this, though.  The only thing that comes close is RT-11 FILEX, but while that handles TOPS-10 tapes (file structured, not raw) it doesn't do the 18-bit systems.  It doesn't actually matter much, but 16, 18, and 36 bit all use the same block size and block count (256 16/18 bit words, 578 blocks) while 12 bit layout has an entirely different block size and count.  But with SMOP you can handle any of these, as indicated by a compatibility table in the DECtape manual.

	paul