Christian writes:
> It is my understanding that so far, the most promising path
> is a PA-RISC emulator. In that kind of software, only the
> 150-odd PA-RISC instructions are emulated, and perhaps a few
> other parts (low-lev I/O ? drivers ?) that may be necessary,
> not "everything" per se. But emulating PA-RISC is enough
> to enable MPE to run, and it's probably the easiest and
> shortest way to market.

Yes, exactly, but...  The "150-odd PA-RISC instructions" are the easy
part, requiring comparatively little development effort.  It's not quite
a "weekend project" but the instruction set is well specified, nicely
modular (you only have to worry about one instruction at a time), etc.

The parts that are *hard* are the rest of the hardware system visible to
software.  This means parts of the system chipset, each I/O interface,
and the actual peripherals attached to those interfaces.

These devices such as the SCSI interface, the LAN interface, and so
forth, are each as complicated in their own right as the PA-RISC
instruction set, and for the most part there's no documentation
available that tells you what you need to know to simulate them.

So a PA-RISC emulator is easy.  An HPe3000 complete hardware emulator is
much, much more difficult.

G.