[Coco] Suggestions?

[Mark McDougall]

On 22/06/2014 5:52 AM, Nick Marentes wrote:

> How about a Vectrex game system?
>
> It's runs a 6809 and once you have it emulating the vector graphics display
> system, will be able to run the entire library of Vectrex games.

I'd love to do the Vectrex but there are technical issues that would be very 
difficult to overcome.

For starters, it's extremely sensitive to the games cycle counts. Secondly 
yes there is a BIOS for vector routines but a lot of games - especially the 
(in a lot of cases, vastly superior) homebrew games - bypass it entirely. So 
with a 1.5 vs 1.89 MHz CPU, there's problem to start with, plus the fact you 
need to emulate the vector hardware.

How do I know this? Because I've written a "working" FPGA implementation 
based on John Kent's 6809 core, which is not cycle accurate. The games are 
definitely recognisable, but the text is completely illegible. There's a lot 
of ballast code in the text rendering BIOS calls that is completely thrown 
out on non-Vectrex hardware.

A pity, but it would be almost impossible to do IMHO. Maybe you'd get a 
particular game running with enough tweaking, but a generic Vectrex engine 
would be out of the question.

Regards,

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