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Re: ColdFire / m68k

John Paul Adrian Glaubitz wrote:
> How much are these instruction set compatible with the classical m68k
> processors? Would we be able to have an m68k port of Debian which runs
> both on the original m68k CPUs and the ColdFire series?

AFAIK the ColdFire is nearly, but not quite, a strict subset of the
m68k. There appear to be a fairly small number of instructions which
behave differently. See here:


Supervisor mode is quite different but that won't affect user mode
applications (i.e. stuff that Debian is interested in).

So at first glance it looks like it would be possible to generate
ColdFire code which would also run on a 68k. The compiler would have to
be careful not to rely on behaviour which was different on the two
processors. A quick glance at the gcc options doesn't show any obvious
flags to do this, unless -march=isaa -mtune=68000 works.

Incidentally, microapl do make a (sadly commercial) product which allows
you to run 68k code on a ColdFire, which works by trapping unimplemented
instructions in software. It's pitifully slow by all accounts but it
does seem to work.

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