RE: [colorforth] Machine Forth 'IF'

[Fréderic DUBOIS <frederic.dubois@xxxxxxxxxxxxx>]

Please disregard. I realized that I described ( a heavily brain damaged)
JUMP. SC was a constant scaling factor. But My first question stills stand (
curiousity).


> -----Message d'origine-----
> De : Fréderic DUBOIS [mailto:frederic.dubois@xxxxxxxxxxxxx]
> Envoyé : mar. 25 février 2003 08:52
> À : 'colorforth@xxxxxxxxxxxxxxxxxx'
> Objet : RE: [colorforth] Machine Forth 'IF'
> 
> 
> I see serious cons against relative branches, which is that 
> it needs an ALU,
> either a dedicated one either the main one. Is it a real problem?
> I've thought of an indexed if in two instructions. The first 
> computes an
> address based on the TOS and the IP. It would do roughly 
> MSB(TA)=MSB(IP)
> LSB(A)=TOS*SC+LSB(IP) where A is the target address. Then we 
> have a second
> instruction which jumps to the address given by the TOS. It 
> contradicts my
> first assertion about relative branches, althought.
> 

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