Re: //e enhancement kit

[dempson@actrix.gen.nz (David Empson)]

In article <2t91q4$5od@maxwell5.ee>, Dan P. Scholnik <dpscholn@mtu.edu> wrote:
> 	I recently got ahold of an unenhanced //e, and being a II+ user who
> hadn't kept up on the later Apple IIs, I don't know what the big difference
> is. A)what is the enhancement?   B) can one still get it?
> as far as I can tell right now, it is just like a II+ w/language card.

The IIe is basically a 64k II+ with full ASCII keyboard (128
characters) and upper/lowercase display.  It has two software
selectable character sets: one is the same as the II+, providing
inverse, flashing and normal text.  The other doesn't have flashing
characters, but provides inverse lower-case characters.

It also has built-in 80-column firmware: you need a 1k memory expansion
card in the auxiliary slot to be able to use the 80-column display.
This card is usually called an "80-column text card".

If you have a 64k memory expansion card (usually called an "extended
80-column card"), then you can also use double high-resolution
graphics (twice the horizontal resolution with a monochrome monitor,
or 16 colours and the same resolution with a colour monitor).

In addition, the IIe can bank switch between the motherboard RAM and
the 64k of RAM on the card (usually called "auxiliary memory").
ProDOS can use this memory as a RAM disk, and many programs use it for
memory expansion.  (Some programs require 128k, e.g. AppleWorks 3.0
and ShrinkIt).


The IIe enhancement kit consists of four chips:

A 65C02 microprocessor, which replaces the 6502.  The 65C02 uses less
power, and has a few new instructions and addressing modes.  Programs
which require an enhanced IIe usually do so because they contain
65C02 instructions, which cannot be executed on a 6502.  The latest
versions of ProDOS (2.0 and later) require a 65C02.  The 65C02 is also
used in the Apple IIc.  The IIgs uses a 65816, which is a 16-bit
version of the 65C02 with even more instructions and addressing modes.

Two ROMs, replacing the "CD" and "EF" ROMs in the IIe.  These contain
Applesoft BASIC, the system monitor, and the 80-column firmware.  The
main improvements are:

- Applesoft and monitor commands may be entered in lower case.
- Monitor has a few minor commands added.
- A mini-assembler is added.
- Major improvements to the speed of the 80-column firmware.
- Interrupt handling is improved.

The fourth chip is a replacement to the video ROM.  A set of special
characters called "MouseText" are added, replacing one of the two sets
of inverse uppercase letters.  MouseText includes apple logos, arrow
symbols, and several characters which can be used to draw windows and
menus on the text screen.


Sources: Quality Computers sell the entire enhancement kit.  Alltech
Electronics can sell you the individual chips.  I wouldn't recommend
upgrading a IIe in piecemeal fashion - it is better to upgrade all
four chips, otherwise programs are likely to make incorrect
assumptions about what machine they are running on, and may crash.
-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand