12 Jun
2009
12 Jun
'09
8:40 a.m.
But other examples exist of non-native OSs running
totally or
partially inside VMs:
- MC68K code on classic MacOS running on a PowerPC, where the OS
hosts an emulator at a very low level, through which most of the
actual OS code itself and many applications run;
- the MC68K emulator on PalmOS 5 on ARM;
- AlphaMicro's MC68K emulator on Intel x86 machines for running AMOS;
- Charon-VAX running VMS on a VAX emulator under VMS on an Alpha.
All these could be considered as straddling the line between a pure
one-platform-on-another sandbox-type emulator and an OS that can run
non-native code side-by-side with native code, no?
I think the dividing line between the 2 is pretty blurry...
I agree, but then there's also the dividing line between a VM and
virtualization. Actually, I'm not surprised to hear that some emulation
had to be done for x86 originally -- the ISA certainly doesn't lend itself
well to virtualizing out of the box ;-)
FWIW, a small correction: Alpha Micro's 68K emulator actually runs at a
somewhat higher level than the others. While it is analogous to the
Power Mac 68K emulator in what it does, it runs more at the AMOS equivalent
of userland, in implementation thus more like Apple Rosetta/QuickTransit.
--
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Cameron Kaiser * Floodgap Systems * www.floodgap.com * ckaiser at floodgap.com
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