[Coco] CoCo Questions

[Phill Harvey-Smith]

Robert Gault wrote:
> PaulH96636 at aol.com wrote:
>> In a message dated 10/28/2006 12:23:19 P.M. Eastern Daylight Time,
>>  cappy2112 at gmail.com writes:
>> 
>> Key-264K gives you two banks of 32k ram (in a 64k machine) which
>> can operate independently of each other, or be interactive, in RS
>> basic, with some  additional commands. -ph
>> 
> 
> There are other programs that did more or less the same thing. The 
> principle is simple, use the RAM/ROM mode and swap between two pages
> of RAM at $0000-$7FFF. The SAM switch for this is $FFD4-$FFD5. The
> Coco3 does not emulate this function.
> 
> Making interactive communication between the two pages would be
> tricky because any changes made to RAM in one page would be lost
> after swapping to the second page. You would almost be forced to
> store common data in a disk file which would be written to before a
> page swap and read immediately after one.

Well You could have a small copying routine in ram that would disable
interrupts, and then switch to map type 1 whilst copying, as then the 
other 32K would appear in the 32K-64K region, and could therefore be 
accessed at the same time, I would not have thought that this would have 
been too hard to arrange.

Cheers.

Phill.

-- 
Phill Harvey-Smith, Programmer, Hardware hacker, and general eccentric !

"You can twist perceptions, but reality won't budge" -- Rush.