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

[John Collyer]

The extra memory can be used for whatever you'd like,
as far as I know there aren't any current applications
using this memory except for VIDEOTEST  and
MEMTEST by Robert Gault.

----- Original Message ----- 
From: "john donaldson" <jadonaldson at charter.net>
To: <coco at maltedmedia.com>; "John Collyer" <johncollyer at zoominternet.net>
Sent: Friday, October 24, 2003 9:34 AM
Subject: Re: [Coco] 6309 microprocessor project - 10-24-2003


>    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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