[Coco] CoCo 3 MMU test for all

jdaggett at gate.net jdaggett at gate.net
Sun Jan 20 17:25:12 EST 2008


On 20 Jan 2008 at 15:49, Mark Marlette wrote:

> Roger,
> 
> I haven't been following this that close because it is something I do
> everyday.
> 
> As james has indicated, basic CoCo understanding of the CoCo's 
> internal registers. A stock MMU is only 6 bits wide. 'AND' off the
> upper two bits, bit6 & bit7.
> 
> Go to a 1 meg machine and bit0-6 will be used.
> 
> Go to a 2meg machine and bit0-7 will be used.
> 
> 256 blocks of 8k sized blocks = 2megs.
> 
> Mark
> Cloud-9


Correct. Any expansion of the memory map beyond 512k will use the two 
other bits not u sed by the GIME chip, thus resulting in four 512K banks. 
Conversly it is also 256 8K banks. 

james




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