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From: Marko_Mäkelä
Date: 1998-09-15
Subject: Re: Snapshot files for emulators

Hello!

> Right: I did not think about the $FF1E, because my emulator is a line-
> based one, and calculates $FF1E values, when the processor reads.
> (Writes are not handled... That would be a hard job.) Can be stored
> at the memory area of $FF1E in RAM dump, like other processor-
> readable regs.

But what if someone later discovers a way to write to the RAM below
$fd00-$ff3f? The RAM addresses 0 and 1 can be written to, and for that reason, you should also store the processor's on-chip I/O register contents separately.

> Timer value is stored. See TIMER1_MAX field. Others are running free.

Yes, but their current value is not stored, unless I missed something.

> What kind of other internal states? I think all was stored.

For example the sound emulation state. Just yesterday there was discussion of it on this list. If you want that the emulation is exactly in the same state after restoring a frozen configuration as it was before freezing, you must store all relevant state information.

> Tagged format would be good, but I think there is no reason for.

I think so. You can't know at this point what kind of state informations are required, and if a cycle-based emulator will ever be written, it must store more status information than a line-based one.

Marko