Re: [hatari-devel] EXA demo Entracte : Improvement in search

[Laurent Sallafranque <laurent.sallafranque@xxxxxxx>]

Oups, right ;)



Le 05/02/2017 à 19:56, Nicolas Pomarède a écrit :
> Le 05/02/2017 à 19:43, Laurent Sallafranque a écrit :
> > I've got the same value for D0, ie $3e65.
> >
> > What I find strange is that D0 increase in a loop that waits the time of
> > a VBL, and it only increase 15 973 times during a VBL ($3e65) ?
> > I would have expected a much higher value.
> > At least, the add is a word add, so it may overflow many times during
> > the test, which also means that the accuracy will have to be very
> > precise if we must reach this $4100 to $4200 area after many "overflow
> > loops"
>
> it's normal to have sthg around $4000 : VBL has ~320000s cycle at 16 
> MHz and the loop takes between 18-20 cycles (it's not just a addq, you 
> have 4 instructions in the loop)
>
> 320000/20 = 160000 = $3e80, so $4100-$4200 is correct, there's no 
> overflow