Re: [f-cpu] the wrong way (or not?) concerning FP

[nicO <nicolas.boulay@ifrance.com>]

Juergen Goeritz a écrit :
> 
> On Mon, 27 Aug 2001, nicO wrote:
> 
> > An other trick could be used : It's to implement the full set of
> > instruction but when a none present instruction is decoded a specific
> > execption is raised and a specific code is runned. This code could be a
> > part of the fcpu and not from a compiler. So you keep the complete
> > compatibility. That's what has been proposed a long time ago.
> 
> Ain't that some kind of microcode then?
> -> That means it has to be coded -> developed
> 

Nono ! Nothing to do with microcode. It's normal code run like exeption
handler !

> It's better to just have the exception but no built-in
> code. Emulation per software (e.g. it's also implemented
> in LEON this way) is preferable BUT introduces additional
> overhead.

Yep, and you lose compatibility (compiling for a low-end f-cpu and
you're will slow down on a high-end fcpu)

nicO

> 
> JG
> 
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