tm_gccmail@mail.kloo.net tm_gccmail@mail.kloo.net
Tue Sep 16 18:23:00 GMT 2003

On Tue, 16 Sep 2003, Joel Sherrill wrote:

> Gunther Nikl wrote:
> > On Tue, Sep 16, 2003 at 07:49:17AM -0500, Joel Sherrill wrote:
> > 
> >>mc68030: We use this to distinguish 68030 from the 68020+FPU and
> >>  68040.  There are some subtle differences that matter.
> > 
> > 
> >   So -m68030 was really used and the build depends on mc68030 beeing
> >   defined?
> As a disclaimer, I do not have the 680x0 docs in front of me and
> this code is old.
> The RTEMS cache management code has unique code for the mc68030.
> According to the comment, the mc68020 does not have data cache
> while the 68030 does.  Further down, there is another block of
> code for the mc68040 and mc68060 which use the same code.


IIRC, the 68020 has 256 bytes of Icache, and the 68030 has 256 bytes
of Icache AND 256 bytes of Dcache.

> Also, I recall that the FPU in the 68040 is not functionally
> equivalent to the 68881/2 or 68030 FPU and some instructions
> have to be emulated.

This sounds right too. Also, there's the explicit instructions to create
and destroy the stack frame which were removed on the 68040 because nobody
was using them.


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