| The Apple II
Plus is an upgraded version of Apple's first mass produced
computer the Apple II. It was released approximately 2 years
after the release of the Apple II in June of 1979. The computer
is actually the same as it's predecessor with a few 'enhancements'.
One improvement was the amount of RAM
on the system board. It came standard with 48 kilobytes of RAM, on the mother board, and could be expanded to a full 64 kilobytes by
inserting a 16 kilobyte expansion card into slot 0 and using a bank
switching technique to trick the MOS Technology 6502 processor into
This was necessary because the 6502
processor is an 8 bit chip with only 16 address lines which limits it to
be able to address only 65,536 (64k)address locations. And since the Apple
II Plus uses 16 kilobytes of those locations to store it's ROM
instructions, only 48 kilobytes of space is left for RAM usage.
But the engineers at Apple came up with this neat little trick of
swapping 16k blocks of RAM into the address area reserved for ROM as needed to give the
illusion that there is a full 64k of RAM available for
The ROM was rewritten and gone
was the hand assembled BASIC written by the man who invented the Apple
Wozniak, replaced with a new integer BASIC
written by a small software company owned by..... [ you hard core Apple
types should look away now :-) ] ...Bill
auto-starting routine was added to the ROM
to speed up booting and a spring was put under the reset key to solve
that little problem that must have annoyed the early Apple users who
would accidentally hit the reset key and lose hours of typed work.
This Apple II Plus is one of two
working models I have in my museum. I was able to put them together from
three broken ones and some spare parts acquired from Ebay auctions. I
would like to thank Brandon Cobb, Ron Watson, and
Ackermann for their contributions to this exhibit.