[Coco] CoCo 3 MMU test for all

jdaggett at gate.net jdaggett at gate.net
Sun Jan 20 15:37:16 EST 2008

On 20 Jan 2008 at 8:29, tim lindner wrote:

> Roger Taylor <operator at coco3.com> wrote:
> > At the stock WIDTH 32 prompt, type:
> > 
> > ?PEEK(65441)
> I get 121 also.
> -- 
> tim lindner
> tlindner at macmess.org                                   Bright

That is what you should see when block $39 is programmed into $FFA1 and 
the MMU will be pointing to $72000 to $73FFF.

121 is decimal for hex 79. Since the upper two bits are invalid the actual 
block is hex 39. It is possible that the GIME returns 01xx xxxx  when a read 
of the MMU register just to keep the software  happy. 

Also a 128K and a 512K machine will always default with the top of memory 
at $7FFFF. Therefore the 128K memory map is from $6000 to $7FFFF. A 
512K map is from $00000 to $7FFFF. SECB runs with the assumption that 
all machines are 128K memory. Only programs that use the balance of ram 
will know if the Coco is a  512K or not. 


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