[Coco] 6309 microprocessor project - 10-24-2003

[Roger Taylor]

At 02:23 PM 10/24/2003 -0400, you wrote:
>John,
>   I thought there was a MAX size that a program could be
>under OS9. Are you saying that now we can have a multi 100K
>program running at the same time. I always was told that
>64K was the max size a program could be.
>
>John Donaldson


The CPU address space is 64k, so that's the limit of code and data that can 
be mapped in at a time, but you can build super large programs using a 
modular approach where components of the overall program communicate with 
each other using various techniques.

One way out of a hundred to visualize this would be the main program 
talking to the submodules through a modem, where the modem is not a serial 
device but some method of sharing common or even isolated information, all 
handled in software, ofcourse.  Packets can be swapped, or the same 
variables/symbols can be shared if all components are assembled using the 
same definition file, etc.

Projector-3, and Mike K's Ultimuse use similar methods of allowing programs 
much larger than 64k to be run.  Mike's program runs under OS-9.  Mine is a 
DECB program that uses it's own memory mapping scheme.  Both programs are 
really only limited to a size determined by the floppy disk or hard drive 
they are stored on.  They could grow "forever" ...