[Coco] Learning CPU Architecture and Digital Design

[Mark McDougall]

On 20/02/2013 11:34 AM, jdaggett at gate.net wrote:

> I made my judgement based solely on the source code. John makes
> comments in certain areas where the CPU09 does things in one or two
> cycles faster than the 6809. So I do know that it was not 100% cycle
> accurate.

I'm not really sure how many instructions are 'off', just going on
empirical evidence from my Vectrex and the fact that things like
SockMaster's Bouncing Ball demo need to be 'fixed' on Coco3FPGA. Taking
nothing away from John's effort of course!

On the Vectrex implementation there were other factors at stake, such as
the delays and decays of the X/Y integrators, however I did attempt to
'calibrate' and compensate for those in my code. However it was clear that
there were other significant timing inaccuracies (CPU) involved. It's
unfortunate that the Vectrex is particularly sensitive to these; far more
so than raster-based systems like the Coco.

> I have yet to actually use it in a real application.

I've given it a good work out in the Williams games, plus Tutankham, Juno
First and Coco 1/2. And of course there's System09 running FLEX and
Coco3FPGA. I've also heard it's used in some Williams pinball circuit
emulation. So it's definitely a core that's holding up well!

> Congradulations on the new child. Get sleep when you can.

Thanks! Coming up to 10 months now and we can almost claim our nights back! :O

Regards,

-- 
|              Mark McDougall                | "Electrical Engineers do it
|  <http://members.iinet.net.au/~msmcdoug>   |   with less resistance!"