Re: [f-cpu] optional SRB

[Antoine <antoine@rezo.net>]

> But I was thinking that we have "ret" for that purpose and in fact SR will be 
> very slow. Of course, this can't be taken from "user" register because we 
> can't trust them, but I don't see the need to access it throug SR.

I've just looked at the manual... In fact, there is "rfe", but it's 
defined to use the SRB ;-))))))))

SRs will be slower than general purpose registers, but they won't be
used very often either ; also, the advantage is that it should be easy
to add/remove SRs (because the unit is separate and doesn't need to be
light speed-fast). Of course with the SRB context switches are faster, 
that's the whole point of it ;)

It seems sensible to do at first without the SRB, and then add the SRB
if it's really too slow. But I don't write the VHDL, anyway ;)

> 	In fact, SR can be used by ordinary code, specially by one that adapt their 
> SIMD code.

Well, yes, but the SRs which are usuable by ordinary code must be 
clearly specified in the coding conventions.



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