Gavin wrote:

> 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.

I wonder if HP could help to ease the platform emulator development
by adding a few "dummy drivers" to the lower level I/O systems of
MPE/iX, while the OS is still HP supported... Something in the line
of NULL_DISK, NULL_TAPE, NULL_TERM... drivers that won't work on the
native PA-RISC hardware or maybe just act as a /dev/null or /dev/zero
type of implementation... but that do provide a kind of "hook" for
the emulator writers in such a way that they pass their parameters
to a well-known hardware address or somesuch.

If not a permanent solution, this might at least shorten the ramp up.

The MPE/iX instances running on a platform emulator would then have
to be using the respective "dummy drivers" in their SYSGEN or NMMGR
configurations, instead of the current ones for real devices like
SCSI disks, SCSI tapes, etc etc.

Lars (only speaking for myself; ignore my eMail address)