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What is stored in the IIgs PRAM? I'm going to replace my PRAM battery in a ROM 03 IIgs and that got me thinking about what is stored in PRAM. I know that date and time are stored, but not if all the same values are stored on the IIgs as on the Macintosh.

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What is stored in the IIgs PRAM?

Basicly everything you can set via the Control Panel

I'm going to replace my PRAM battery in a ROM 03 IIgs and that got me thinking about what is stored in PRAM. I know that date and time are stored, but not if all the same values are stored on the IIgs as on the Macintosh.

It's much like the Mac. In addition to things like language, colours or interface parameters, more hardware related setup values are also stored. This includes speed and asignment of function to slots and so on. For example I remember offset $28 beeing the boot slot.

The only description of the data I could find is the description of the control panel in Apendix G of the IIgs Firmware Reference (p299ff). But it goes only by the handling of said ROM programm, not how it's stored. You might want to do some web search to find more. When doing so it might be a good idea to include BRAM as term, as it was thuout documentation usually called 'Battery RAM' (*1).

AFAIR the first $20 are the clock part and the control panel uses the area up to $60 or so. Everything thereafter is initialized with $FF. Except for the last 4 bytes containing some checksum.

A helpful tool might be Sheppy's Shifty-List, as it, IIRC, allows it to save and restore BRAM content among many other setings, so you won't have to worry to miss anything.


*1 - BRAM vs. PRAM is a nice little way to distinguish old time Apple IIgs fellows from Mac people.

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