See my comments below

>1) Would hardware emulation take more processing power than an OS emulator?

Depends on the OS. With a rich feature OS like VMS the amount of code
required to map all functionality accurately would be huge, expensive to
write and to debug, and techniques to speed up execution by dynamically
translating instruction sequences would not work. With 1-2 Billion
instructions per second available the trick is more to keep the code size
small. The total size, including the emulation of the major peripherals, of
the run-time part of CHARON-VAX is < 500 KB and it fits in PC cache memory.

The big advantage of hardware emulation is the ability of fast and
comprehensive testing by running the hardware diagnostics.

>2) Does your VAX emulator provide bridges or gateways to the native OS or

>hardware? (Is such even desireable?)

Those bridges are available and used e.g to store emulated disks as files
(although you can connect physical disks). Serial lines are effectively
telnet sessions, and instead of mapping to the host serial ports you can
link them to host applications. But the goal is to leave the OS of the
emulated system in control; our design goal is always to be able to run any
available OS of the emulated system.

>3) For MPE to run directly (ie. loaded directly from HP tapes) wouldn't you

>have to emulate the entire HP3000 architecture?

Yes, certainly, that is exactly what we do for the VAX and PDP-11 emulators.
For the PDP-11 we emulate over 100 devices (for the VAX less). We generate
each device emulator component directly from its hardware description. A
CHARON-VAX emulator is booted directly from the standard VAX/VMS
installation kit on CD or standalone backup on tape.

>4) Could you emulate multiprocessor 3K hardware config (or, would you need

>to?)

Yes, but you need a host SMP system to benefit from the multiple emulated
CPUs. We run actually clusters of VAX/VMS systems on a single SMP host that
way. It only makes sense if performance is an issue, but if the original
hardware is capable of it, the emulator should be capable as it is a direct
copy.

>5) Seems that if you implement a truely portable HP3K hardware

>implementation, as more modern host hardware becomes available, you could

>end up with a more powerful MPE box than you could ever have with real 3K

>hardware - cheaper too!

Our standard VAX 3600 emulator runs at about 5 times the speed of a hardware
VAX 3600 on an AMD 2000+ system (and probably gets 30% faster every year).
But the 3600 is a slow system (compared to current technology) to start
with. I have not looked into the HP3K designs in detail to be able to give
an opinion here.

>6) How much would we be restricted to peripherals and storage that are

>compatable with a real HP3K, and how much could we use non-3K components

>(ie. tape drives, DASD, NICs, DTCs[less important]?\

It is a matter of documentation and implementation time, there is no
fundamental restriction except for real-time requirements (e.g. connecting
with a parallel interface to an instrument), where the host system PCI
latency might play a role. But NICs, disks, tapes map very well. Emulated
disks are generally faster than physical ones because you can use the latest
technology.

Regards, Robert

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