John asks:
> "The new Series 997 system, which HP will announce next week, is
> based on the 64-bit PA-8000 chip."
>
> Did I miss out on something here?  I was under the impression that
> a) the PA-8000 series chips are 32-bit and not 64-bit, and
> b) HP has no intention of building a 64-bit MPE-iX system in
>    the immediate future.

The PA-8000 chips implement PA-RISC 2.0, which uses 96bit virtual
addressing and 64bit physical and addressing and a full 64bit data
path.  All registers in the CPU are 64bits wide.  It doesn't get
any more "64 bit" than this.

Now, one of the cool things about the PA-RISC 2.0 architecture is
that even though all the general registers in the CPU have expanded
for 32bits to 64bits, all existing PA-RISC 1.x code that expects
there only to be 32bits per register runs correctly.  This is
even accomplished without a special 32bit "mode" of any kind.
There *is* a "mode" bit that switches between old style 32bit
Space IDs with 32bit offsets and 64bit Space IDs with 64bit
offsets, but this only affects the way virtual addresses are
constructed, and not what instructions you can execute.

Because of the inherent compatibility between the 32bit PA-RISC 1.x
CPUs and the 64bit PA-RISC 2.0 CPUs, it probably wasn't that hard
for HP to get MPE running on the new systems.  Since there is only
one version of MPE today that runs on all systems, it's got to be
the same code on all systems which means that MPE running on a
PA-8000 system is simply not executing any of the new instructions
that only work on PA-RISC 2.0 CPUs, such as 64bit LOAD and STORE
etc.

As far as a 64bit version of MPE goes, any such MPE version would
of course only run on HP3000s that had PA-8000 CPU chips, which
means only the most recent midrange and high-end systems.  What
if HP were to move all future MPE development to the 64bit
systems?  If they committed to giving you a real 64bit version
of MPE, but that meant that they might not be able to continue
to enhance the existing MPE for PA-RISC 1.x systems beyond some
point, and this was the only way that a 64bit MPE could ever be
cost justified, would you vote for HP to go this way?  Would you
be willing to upgrade your system at some point to a 64bit one
in order to run the latest (64bit) version of MPE?

> Am I wrong? Or is the PA-8000 one of these 64-bit internal/32-bit
> external gadgets?

Nope, it's 64 bits inside and out.

G.