Re: External drives

["Michael Pender" <mpender@hotmail.com>]

Mark Cummings <NOTfigjams@primus.com.au> wrote in message
news:3f103230$1_1@news.iprimus.com.au...
> > > Does the IIc have to be a certain ROM version to support the unidisk?
> >
> > Yes it does.  Go into Basic and type "PRINT PEEK (64447)" and press
> > return.  If it says 255, you need a ROM upgrade to us a 3.5" UniDisk
>
> is it possible to upgrade the ROMs on older //c's to support the Unidisk
3.5
> or are there other changes to the machine ?
> in other words can I copy the ROMs from my later //c to my older //c to
get
> Unidisk 3.5s to work ?
>
> Mark

First, I don't know if there were circuitry changes to support the Unidisk
in addition to a ROM upgrade.  If its just the ROM it should be possible to
cut & paste the ROM from the new //c to the older //c to get it to work.

I used to do something similar so I could play Karateka on my Laser 128.
I'm a little fuzzy on the details now, but it went something like this:

- Save a copy of the ROM image as a file.
- Find a place in memory to put the ROM code where it won't get switched out
when you press reset
- Modify any absolute address references to point to the new address.
- Change the I/O vectors to point to the start of the code in memory (I'm a
little fuzzy on how I used to do that now)

If the code you need is located in the Applesoft area as opposed to the
memory set aside for slot 6, then there you could use LOADER.OBJ0 to load
FPBASIC into the 16K language card and overwrite the code there.

Can anyone help me fill in the blanks in my memory?

- Mike