Re: What does //c upgrade do?

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

In article <2taheo$fss@spool.cs.wisc.edu>, Rob Jacob <rob@ssec.wisc.edu> wrote:
> Well I finally hauled my Apple//c out of the closet and hooked
> up and found out I have one of those very old //c's.
> (Peek 64447 returns "255")
> 
> The FAQ mentions an upgrade is available but I'm wondering what
> exactly the upgrade does.

It depends which upgrade you get.  The simplest is the ROM upgrade (to
ROM version 0).

This requires making a simple modification to the motherboard, because
the replacement ROM holds twice as much code as the original one.
(Cut a marked option position, and solder another.)

ROM 0 gives you support for a UniDisk 3.5 drive (and other intelligent
SmartPort devices, such as SmartPort hard drives).  It adds a few
commands to the serial firmware, adds a mini-assembler and step/trace
commands to the monitor.  You lose the ability to boot from an external
5.25" drive by typing PR#7.

Any further upgrade requires a motherboard swap.  There is a design
shortcut in the original IIc motherboard, which results in the serial
ports running at slightly the wrong speed.  This can cause problems
with some modems at 1200 bps or faster.  The motherboard swap fixes
this, and will also give you ROM 0.

A later revision of the motherboard includes a memory expansion slot
(under the keyboard), and ROM version 3, which has support for the
memory expansion slot.

There is also a ROM version 4, which is a bug fix release.  The two
bug fixes mentioned in TN.AIIC.007 are a problem with the keyboard
buffering (which may have been present in all previous versions), and
the memory expansion firmware correctly indicating if the expansion
card is not present. 
-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand