[Coco] MC6829 Memory Management Unit

[gene heskett]

On 10/11/22 00:37, RETRO Innovations via Coco wrote:
> On 10/10/2022 10:29 PM, Walter ZAMBOTTI via Coco wrote:
>> Would that technique allow the video circuitry to access all the 2meg 
>> of mem as well?
>
> GIME video uses a "flat" memory model, as I recall, where the data is 
> placed in the physical memory space 0-512kB regardless of task 
> mappings.  So, to extend the GIME to allow 2MB of memory access, you 
> just create a register with 2 bits, and those 2 bits are used as a 
> video "bank" register.  The GIME can only access 512kB at a time, but 
> it can access it anywhere within the 2MB memory address space, with 
> the requirement that memory access cannot span 2 512kB banks.
>
> Jim
>
>
Somehow, in running myram set for a 1.5 meg ramdisk, I never ran into 
that limit. Probably saved by the size limits imposed by the c compiler.
It got distinctly unhappy with src files exceeding 24k. Even cprep-19 
puked over that.

Cheers, Gene Heskett.
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