> True for the older processors - I believe that later processors do not
> overload the FPU registers in this manner.

That's arch dependend and not generally true. On sparc64 for example the
kernel already does all the bookeeping and uses VIS instructions (roughly an
MMX equivalent) in -current. On i386 it doesn't, so MMX instructions can
not be used.

Newer processors (on i386 at least) still overload MMX registers and FP stack
(and I don't see a way to add new registers that need saving on context
switch without breaking binary compatibility).


Martin