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Re: Installing GS RAM card in slots 1-7

rich12345 wrote:

On May 22, 12:28 pm, "Charlie" <charlieD...@verEYEzon.net> wrote:

I'm having trouble getting my mind wrapped around this statement.
Could you clarify it?  Specifically why is it necessary to access
both the AUX memory and main memory in the same cycle?


AUX RAM and MAIN RAM need to be accessed in the same cycle
for 80 column text and DHGR graphics.

1/2 of the video data is in MAIN, the other 1/2 is in AUX.

Same cycle:  It takes 2X the time to display 80 columns compared
to 40 columns.  It takes 2X the time to display DHGR compared to
HGR....


Actually, it takes 2x the number of *bits*, in exactly the same time
(1 cycle), so the need to access both main and AUX memory concurrently.

Only one address bus is needed, but two data busses are required.


If you access AUX at a later cycle, then you add to the time to
update/refresh the video output.


(maybe?)


Very close.  ;-)

-michael

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