[rescue] SMP on intel wasteful?

[Dave McGuire]

On June 24, Alex White wrote:
> > > ROM came only with the 11/750, which was after '78 as far as I know.
> > 
> >   The 11/750 was indeed after the /780.  It also booted its microcode
> > and monitor from a separate (i.e. non-CPU) device...a TU58 tape drive.
> 
> Actually there's boot ROM sockets on the memory controller. One of the
> front-panel switches selects which ROM it boots from (the device
> switch).

  Looking at the 11/750 print sets, I find that you are indeed correct!
I had forgotten all about this.  Upon powerup, the contents of those
four ROMs are copied into main memory after the CPU locates 64KB of
good memory and does a few other little things.  Then the position of
the Boot Device switch is read and the CPU executes that chunk of
code, if there was a ROM in that socket.  ROM socket 1 always contains
the TU58 bootstrap if memory serves.  Man it's been a long while since
I booted a '750.

  Come to think of it, I believe it was the '730, not the '750, that
booted its VAX instruction set microcode from TU58.  I think the way
it worked with the '750 is that it could load updated microcode or
microcode patches from the TU58 or the system disk (PCS750.BIN comes
to mind) but the base VAX instruction set microcode is indeed in ROM.
It has been FAR too long.

         -Dave

-- 
Dave McGuire                  "Needing a calculator indicates that
St. Petersburg, FL              your .emacs file is incomplete." -Joshua Boyd