[Coco] CoCo Questions

[PaulH96636 at aol.com]

Actually I've used Key-264 for my own inventory programs which let me use  
the upper 32K
for data while the basic program resided in the lower ram.  But  another 
program found that
it was better to copy certain lines from the main program in the lower 32k  
into the upper 32k
and self-delete the copied lines to free up more memory in the lower  ram.  
Key-264k is a ml
loader which occupies about the same memory as one graphics page in each of  
the banks
allowing the user full interaction, or use two separate programs, one in  
each bank.  In the
case of graphics, one can even use the extended commands to view what is  
going on in the
bank not currently being active. You could, for example, print text to  a 
printer from a program
in one bank, while composing another page in the other bank.  Yep,  that's 
multitasking.
There was far more data space available than by using basic-09/Runb which  
also accessed 
 64k  but took up much more memory than two graphics pages  would.    -ph
 
 
In a message dated 10/28/2006 8:49:42 P.M. Eastern Daylight Time,  
afra at aurigae.demon.co.uk writes:

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.

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