[Coco] Re: Any reason to put a 6309 in a Coco2?

[Brad Grier]

Torsten Dittel wrote:


>>Interesting. Microsoft was notorious for doing this with their ROM

>>Basics.

> 

> 

> I think the opcodes in Microsoft BASIC weren't illegal, they just did

> something useless. AFAIR some of the so called "illegal" instructions of

> the 6809 had some effects on the registers including the CC which just

> didn't make sense. I once saw a list somewhere were all the "functions"

> of those opcodes were listed. I wonder if the emulators do this well.

> Tim? Brad?

> 

> Torsten

> 

> 



There's some documentation for the illegal opcodes at:

http://koti.mbnet.fi/~atjs/mc6809/Information/UNDOCOPS.TXT

I believe I implemented just one or two of them in Mocha in order to get 
a specific game to work. I probably should add all the ones that make 
sense - I think I was worried about performance.

Brad