On 1997-10-29 mcguire@neurotica.com said to port-vax@netbsd.org
   >On October 29, you wrote:
   >> <I was always told that about the 11/750 as well.  However, we
   >>got one that  <was being discarded by the chem department when I
   >>was an undergrad.  We  <plugged it in, turned it on, and it
   >happily booted VMS from its disk.  Is >
   >> I'll bet someone put a tu58 hardware emulator or other mod in
   >>there.  If  there is no tape in a stock 750 it just looks at you.
   >Yes...the 750 loads microcode from the TU58 when it starts up...It
   >doesn't even know the full VAX instruction set until it spins that
   >tape, as I understand it.

That's strange... my 11/750 also booted just fine without loading TU58
tapes. B DUA0 at the >>> prompt was enough. Must have some sort of
option installed. I always wondered what all the 'console' tapes were for.

   >The TU58 is, however, a *very* simple beast.  It communicates via a
   >serial line using a very simple protocol.  It'd be trivial to
   >emulate that with pretty much any computer with a serial port
   >running a little program.

Where could I find details on this protocol? I always found the TU58 very
unreliable. I tried to build standalone backup many times, and every time
it said the tapes were created successfully, and every time it would not
boot from the set, giving an error message when at the third or fourth
tape. This gets tiring real quick. A computer emulating the TU58 in its
place would be much more reliable. But of course you then get the question
of how to get the TU58 images on the disk of the emulating computer first.

Somewhere I have a cabinet with two TU58's in it and a serial port on the
back. The thing might even work, I don't know. I think Ragge made TU58
images for NetBSD once, maybe an emulator could feed these images to the
11/750. That would be a nice way to get a completely empty 750 to work
again!

Kees

-- 

Kees Stravers - Geldrop, The Netherlands - pb0aia at amsat dot org
PC/Novell system management - DEC PDP-11/VAX preservationist

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