Linards Ticmanis wrote:
http://rich12345.tripod.com/memory/messin.htmlYou left out text page 2 (not so important, I guess) and DHires page 2 (important if you want to page flip)....and the two more banks in the $D000-$DFFF area.
There are 128K of RAM in a fully expanded 8-bit Apple (not counting slinky cards and such), but there cannot be RAM in the $C000-$CFFF area which is reserved for soft switches, real slot ROM, and emulated slot ROM.
This means there are only 64K-4K = 60K of address space in every bank that can be RAM. 60+60=120, not 128; where did the other 8K go?
The answer is the fact that in the address range $D000-$DFFF there are actually *four* banks of RAM in a 128K Apple. Both main RAM and aux RAM have a "reserve bench", so to speak, in this area. This arrangement is a relic of the original language card for the II+, which also had to fit 16K of RAM in only 12K of ROM space.
-- Linards Ticmanis