Re: CONFUSED

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

In article <39qr4c$mae@styx.uwa.edu.au>,
Joseph Turner <jturner@tartarus.uwa.edu.au> wrote:
> 
> I have been thinking of getting a ram upgrade for my 2c. I have one
> of the origianl 2c (So I get 255 from that addres that tells you what
> rom version you have.) Now to be able to add extra ram to my iic, do
> I JUST have to replace by rom so when I peek that specail address I
> get 3?

'fraid not.  You also need a motherboard upgrade.  The original IIc
motherboard doesn't have a memory expansion slot.

There are at least three versions of the IIc motherboard.  The
original one, supplied with the original ROM (255) defaults to a 16k
ROM and has the potential problem with the serial port communications
speed (bit rate is about 3% too slow).  There are a couple of
modifications marked on the motherboard (cut one track and solder
another) which allow a 32k ROM to be used.  This is required if you
want to upgrade the ROM without changing the motherboard.

The second version, supplied with the UniDisk-compatible ROM (0)
expects a 32k ROM and has a crystal on the serial ports, correcting
the speed problem.

The third version, supplied with the memory expansion ROM (3) expects
a 32k ROM, has fixed serial ports, and has a memory expansion connector.

ROM version 4 fixes bugs in version 3.  IIc ROMs 0, 3 and 4 will work
in all versions of the motherboard, but the memory expansion features
will not be available in older motherboards.

> Someone told me that getting this new rom  would ONLY allow me to use a 
> 3.5 drive...

Correct.  A UniDisk 3.5 drive can be used on the IIc, if it has ROM
version 0, 3 or 4.  ROM version 0 also adds a few commands to the
serial port firmware, and a mini-assembler.


There is another option: Applied Engineering used to make a memory
expansion card for the original IIc motherboard.  It plugs into the
microprocessor and MMU sockets under the keyboard, and the chips are
then plugged into the memory card.  I think it is called the Z-RAM, or
something like that.

This card works like the RamWorks card for the IIe, i.e. it is a
multiple bank auxiliary slot memory card.

Apple's IIc memory expansion card works like the Apple II memory
expansion card or the RamFactor, which are "slinky" cards that provide
a byte-sized window into a slot-based memory card.
-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand