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The 'Extended 80 Column Card'
This is the most common memory expansion the //e has. It consists of an
additional 64K added to the Apple //e. It is many times incorrectly called a '128K
card', it is not. What it does is, when added to the Apple //e, the total memory
available to most programs increases to 128K. 70% of all //e specific software knows
how to use this card, where-as 15% of //e specific software knows 'about' any
memory past the 128K. AppleWorks 3.0 & Publish-It 4 are two examples of programs
that require ATLEAST 128K but will use more memory if it is available.
When a program says "Requires 128K" This is the card you need to make that run.
Also, newer programs required an enhanced //e as well. This is not the same. In
addition to the 80 col/64K card, an enhancement kit may be required.
The 6502 CPU can only access 64K of RAM at any given time. The Apple //e and //c
break this barrier with a method called Bank Switching. While the CPU can only
access 64K at a time, what is happening is the particular Bank of 64K is being
swapped around. The Apple //e, and //c were setup to have two banks of 64K. What
these cards do is swap the active Aux 64K bank around. AppleWorks versions 3.0
and higher automatically do this for you. The Apple IIgs does a similar thing when
working in 8 bit (compatibility mode) but when in native mode, all RAM (up to 8
Meg) is available as one. The 65816 can access up to 16 MB of RAM but Apple's
implementation allows for 8 MB of system RAM and the other 8 is reserved for
ROM, thus the ROM does not have to be transferred to system RAM on power up,
giving the user access to ALL the RAM in the computer, unlike the //e or ][+ which
loads the ROM into various RAM areas on power up. (The IIgs actually does this
too, with respect to the Apple II ROM, to remain compatible, but the IIgs toolbox
stays in the higher banks and are only transferred to RAM if software does it.)
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