[Coco] Emulator

Robert Gault robert.gault at worldnet.att.net
Mon Sep 7 08:50:44 EDT 2009

Wayne Campbell wrote:
> I don't think it's that bad. I think MESS is very stable, and I find it
> enjoyable to use. There are just instances where the behaviour of the
> memory allocations are larger than the original 64K page method in the
> CoCo3 allowed for. While it has not been a problem, I do have to wonder
> if I'm exceeding the limit the original CoCo2 or 3 had in terms of
> available memory. If my procedures get too large, they will not run in the
> original environment. This defeats the purpose of creating the software to
> begin with. I want my programs to run on an original CoCo2 or CoCo3,
> whether it has 64K, 128K or 512K of RAM available. They all have the same
> limitation, and while I never possessed a memory board for the 1M+ sizes,
> I believe it applies to them as well, and that is the 64K page size limit
> imposed by the GIME chip.

The 64K limit is imposed by the CPU not the GIME which allocates $2000 
byte chunks.

Wayne, there is no reason why a large program must exist only in memory. 
Write these large programs in modular fashion and load modules from disk 
as needed to get around the 6809 64K memory limit.
OS-9 is written to make this simple. Even so, this can also be 
accomplished under the Basic ROMs. It certainly is harder under Basic, 
but it is even possible to pass variables between program modules.

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