[Coco] Blast from the past!
cocomalt at 6809.org.uk
Sat Feb 2 10:39:06 EST 2008
jdaggett at gate.net wrote:
> On 31 Jan 2008 at 16:53, Ciaran Anscomb wrote:
> > It does seem odd that they didn't implement the more obvious
> > additional modes (that were already documented in the SAM data sheet)
> > in the GIME, though I can understand not bothering with the more
> > obscure behaviour.
> having been apart of a team that designed a new IC, I can tell you there are
> trade offs in any design.
> My guess is die size and packaging costs dictated what could be done internal
> to the GIME.
Yeah, you're almost certainly right.
The full majesty of my uninformed reckon would have had them make the
addressing modes separate and arbitrarily selectable, but there's almost
certainly a "good enough" approach that would be simpler and thus cheaper.
Just out of interest: the GIME does simulate the SAM internal config
and VDG select lines to some degree, so what does it actually do if you
configure everything to what would be SG24 on a CoCo2?
Ciaran Anscomb, Perl/C Hacker
More information about the Coco