[Coco] Tandy Assembly Exhibit: CocoMEM

[RETRO Innovations]

On 10/12/2017 9:40 AM, William Astle wrote:
> I suspect a lot of "advanced" OS9 programs will fail under proper 
> memory protection. Some of the descriptions of "clever" techniques 
> I've heard over the years lead me to suspect all manner of things that 
> really aren't kosher being (ab)used.
>
> Speaking with my OS development hat on, I would much prefer an NMI on 
> a "segfault" over FIRQ or IRQ.[1] That way a program can't mask it, 
> even temporarily, by disabling interrupts. That will make it a *lot* 
> easier to identify the source of the fault in most poorly written 
> programs since it will always occur immediately after the instruction 
> that triggered it finishes, at least if I have my facts on the 6809 
> straight. Also, the NMI is edge triggered so you wouldn't have to 
> maintain an interrupt state anywhere once it fires.
Great idea.  It would have to be a flying lead, though, as NMI is not 
routed to the GIME (one of the very few signals not so routed) I'm not 
opposed to it, I'll put a post on the finished unit to connect it.

Jim