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

[john donaldson]

   John,
     This may sound like a silly question, but what will 
one
be able to do with the extra memory. Can it be used for
large programs, or is it only useful for graphics screens
and mabey a RAM Disk?/

John Donaldson



On Fri, 24 Oct 2003 08:48:53 -0400
"John  Collyer" <johncollyer at zoominternet.net> wrote:
>6309 microprocessor project.
>
>Hello,
>
>The special opcode $11FD (win32 functions) let you 
>manipulate files
>on the host system directly from your emulated coco 
>programs.  The
>data areas that you defined and initialize according  to 
>the win32 api
>documentation will be converted from Big Endian to Little 
>Endian byte
>order for you automatically, naturally.  This allows you 
>to manipulate
>the win32 data structures in a natural way.
>
>The special opcode $11FF will let you run win32 code, but 
>I suspect this
>opcode will generally not be used heavily by anyone, 
>mostly because it's
>hard to use and awkward.
>
>I am starting on the memory portion of the emulator 
>today. The emulator's
>memory will be designated as read/write/execute, this is 
>to support the
>special opcode $11FF. Below see my vision of coco's 
>emulated memory.
>
>; FF9B  Reserved. | 2^11 = 1000000h = 16777216 = 2048 MMU 
>blocks
>;                 | for a total memory of 2024 * 8192 = 
>16,580,608 (16Meg).
>;
>;       1MB and 2MB bits, Write only.
>;       Bit 7 - 16MB Video Bit           NoCan3 bits for 
>16MB.
>;       Bit 6 - 16MB Memory Bit          NoCan3 bits for 
>16MB.
>;       Bit 5 -  8MB Memory Bit          NoCan3 bits for 
>8MB.
>;       Bit 4 -  4MB Memory Bit          NoCan3 bits for 
>8MB.
>;       Bit 3 -  8MB Video Bit           NoCan3 bits for 
>8MB.
>;       Bit 2 -  4MB Video Bit           NoCan3 bits for 
>8MB.
>;       Bit 1 -  2MB Video Bit   Disto & NoCan2/3 bits 
>for 2MB.
>;       Bit 0 -  1MB Video Bit   Disto & NoCan2/3 bits 
>for 1MB.
>
>The memory bits (vmmmvvvv) at $FF9B have no effect until 
>a value is sent
>to an MMU register, $FFA0-$FFAF. When a value is sent to 
>an MMU register,
>the memory bits at $FF9B combine with the MMU register to 
>create a pseudo
>11 bit register. This enables access to 2048 (2^11) MMU 
>blocks for a total
>memory of 2024 * 8192 = 16,580,608 (16Meg).
>
>I've decided to use the Nocan3 memory model, which gives 
>us access to
>16 Megs of ram plus the 32K internal rom. With this model 
>there is no
>need for the jv coco3 emulator's use of the MMU extension 
>registers at
>$FF70 - $FF7F. That will leave these memory locations 
>free as they should
>be. If anyone would like to comment on my vision of 
>memory for the jc emulator,
>please do! The topic is open and I'd like to read all 
>your responses.
>
>
>More later
>
>John Collyer.

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