Re: Slot settings on a ROM 3

[supertimer@aol.com (Supertimer)]

Pim Blokland <nipp@plane.nl> wrote:

>supertimer@aol.com (Supertimer) wrote:
>
>> Right.  Under GS/OS, you can use slot 4 and keep the mouse
>> on a ROM 3.  The ROM 01 can't do this.
>
>Yes, I know that! But my question was: why? Does the ROM 01 use routines 
>that are located at $ExC4xx? Or does de ROM 3 do some nasty tricks that 
>they hadn't thought of when they manufactured the 01? That's the kind of 
>thing I'm curious about.

It is the firmware.  Possibly the Toolbox.  On the ROM 01,
the ADB mouse is accessed using the emulated IIe mouse
firmware in slot 4.  The IIGS is made to think there is the
equivalent of an Apple IIe Mouse Card in slot 4.  Even the
IIGS operating system must go through this firmware.  The
benefit of this method is that you can switch slot 4 to
'your card' and have a mouse card of your choice.  For
example, if you wanted to use a PC mouse on your IIGS,
on a ROM 01, you can plug in a BitMouse card and
connect a PC serial mouse to it.  You'd then have a two
button serial mouse that can be used in GS/OS.

On the ROM 3, the firmware (Toolbox?) for the mouse was
changed to directly read the ADB mouse.  Thus, under
GS/OS, it will always see the ADB mouse even if you
have slot 4 set to 'your card' and use that slot for a card
of your choice.  HOWEVER, it will not see a PC serial
mouse or use it if you have a BitMouse card in slot 4 and
set that slot to 'your card'.  It will continue to use the ADB
mouse.

Personally, I think nobody would mind losing choice of
mouse controller in return for the use of slot 4 for other
more important purposes.