[Coco] Learning CPU Architecture and Digital Design

[Mark McDougall]

On 20/02/2013 2:16 AM, T. Franklin wrote:

> Curious, Do these "commercial" cores do a better job of emulating the
> clock timing of the 6809 vs the "open source" cores? I'm just wondering
> if paying for a core would result in any bennifit over the open sours
> models.

There's no rule of thumb for cycle-accuracy. The T65 (6502) open core is 
cycle-accurate, and although it doesn't say it, I'm pretty sure the T80 
(Z80) open core has been modified for cycle accuracy. OTOH the 68K open core 
is not, and neither is John's CPU09.

The aforementioned 6809 core(s) from Microsemi are not cycle-accurate, and I 
suspect the Sierra one isn't either otherwise it would most definitely be 
advertised as such. OTOH there are commercial 8080 & 8085 cores which are 
cycle-accurate (for the most part).

Also bear in mind that if you purchase a commercial core, you may not 
necessarily be getting the source code (unless you pay a *lot* of money). 
Some cores are distributed in binary/obfuscated forms that are locked to 
your design or device, hardly suited to an open hobby project.

Regards,

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