multi-core software

rossberg at rossberg at
Mon Jun 8 10:05:44 CEST 2009

On Jun 8, 6:28 am, "Ken T." <nowh... at> wrote:
> > Let's not forget Elite for the 6502 exploiting predictable performance
> > in order to switch graphics modes partway down the vsync!
> That actually didn't require predictable timing.  You could tell the
> video chip to send you an interrupt when it got to a given scan line.  I
> used this myself.  

I don't know what Elite did, but I know for sure that it was a common
trick on the Atari ST to switch color palettes or graphics mode at a
fixed point *in each single scan line* to get more colors, or display
graphics on the screen borders. That required "synchronous
programming", i.e. counting clock cycles of machine instructions such
that for every point in the program you knew exactly where the
electron ray would be.

The Atari ST had an M68000 with exactly 8 MHz, which made this
possible. There were no caches in those times, and clock cycles were
entirely predictable.

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