Re: Weird thing happened on my 2gs rom3

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

AMart79196@gmail.com <AMart79196@gmail.com> wrote:

> [...] when I hit the openapple- control-esc, I found instead of three
> options there, there was 5 options there.
> I always though that those options were written into the ROM and that
> anything else that popped up there was static and would erase on a
> reset or turning off the machine.

Correct. The extra two items you are seeing are also built into the ROM
on a ROM 3 IIgs, but they aren't supposed to be displayed unless you
enable them.

I forget their exact names, but they are debugging tools.

The official way of enabling them is to use the # command in the
monitor. They will then appear in the CDA menu until you power off the
IIgs.

I remember that a long time ago we were investigating the same problem
on this group - for some people (notably Mitchell Spector, I think?)
with a ROM 3 IIgs, these CDAs were always appearing, while others
(including mine) were behaving normally.

We eventually tracked it down to a bug in the ROM 3 firmware. The
appearance of these CDAs is controlled by a RAM location somewhere in
the $E0 or $E1 bank, and it happens that there is no code to initialize
this location on power-up. This means that the initial content of that
location depends on the random contents of dynamic RAM when power is
applied.

It seems that for most ROM 3s, this location starts up containing zero,
which disables the debugging CDAs, but some others consistently come up
with a nonzero value, which enables them. In some others it might be
random.

Try doing a search through Google's archives for the old thread for more
details. I think it predates my saved copies of my own posts.

-- 
David Empson
dempson@actrix.gen.nz