Re: Why VAX Was the Ultimate CISC and Not RISC

anton@mips.complang.tuwien.ac.at (Anton Ertl) writes:

If you sent, e.g., me and the needed documents back in
time to the start of the VAX project, and gave me a magic wand that
would convince the DEC management and workforce that I know how to
design their next architecture, and how to compiler for it, I would
give the implementation team RV32GC as architecture to implement, and
that they should use pipelining for that, and of course also give that
to the software people.

There was also the question of PDP-11 compatibility.  I would solve
that by adding a PDP-11 decoder that produces RV32G instructions (or
maybe the microcode that the RV32G decoder produces).  Low-end models
may get a dynamic binary translator instead.

OTOH, DEC had great success with the VAX for a while, and their demise
may have been unavoidable given their market position: Their customers
(especially the business customers of VAXen) went to them instead of
IBM, because they wanted something less costly, and they continued
onwards to PCs running Linux when they provided something less costly.
So DEC would also have needed to outcompete Intel and the PC market to
succeed (and IBM eventually got out of that market).

OTOH, HP was also a big player in the mini and later workstation
market, and they managed to survive, albeit by eventually splitting
themselves into HPE for the big iron, and the other part for the PCs
and printers.  But it may be the exception that proves the rule.

- anton
--
'Anyone trying for "industrial quality" ISA should avoid undefined behavior.'
  Mitch Alsup, <c17fcd89-f024-40e7-a594-88a85ac10d20o@googlegroups.com>