recursive emulation

Liam Proven lproven at
Fri Jan 27 06:26:28 CST 2017

On 25 January 2017 at 00:19, Jecel Assumpcao Jr. <jecel at> wrote:
> In the RiscPC era they used actual Intel processors instead of (or was
> it as an alternative to) software emulation.

The Risc PC had a 2nd processor slot. It wasn't able to be a full SMP
machine, but there were options for a 2nd ARM chip (which would have
to be custom programmed), a 3rd party multiprocessor board:

... Or Acorn's own official "PC card".

I actually have 2 or 3 of these, boxed, awaiting restoration of my RiscPC.

The card didn't do much for RISC OS, but allowed a native-CPU-speed PC
emulator app. The card had a real processor, but used
software-emulated I/O -- disks, screen, sound etc. -- so it wasn't
very compatible. It would run MS-DOS, Windows 3 and 95. Win98 very
slowly with significant caveats. Win95 ran in a minimally acceptable
mode, using "MS-DOS disk and file access" -- in other words, dropping
to BIOS calls, as there was no real disk or screen hardware for its
VxDs to address and control.

There is/was a commercial app to use the PC Card's onboard FPU to
accelerate RISC OS FP operations:

This is only faster on ARM6/ARM7 RiscPCs, though. StrongARM machines
could do faster FP in software.

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