Snapshot incompatibility

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codemarvin
2012-06-28
2014-08-10
  • codemarvin
    codemarvin
    2012-06-28

    Hi,

    over the years I have created several x64 snapshot files (VSF) for documentation purposes, for quick starting applications and for saving game progress. I am using VICE / x64 on Linux platform and this all worked very fine up to version 2.2 of VICE.

    Starting with official VICE version 2.3 (tested up to development release 2.3.18) it seems now impossible to load any of mine existing snapshots:

    AUTOSTART: Restoring snapshot.
    Error - Snapshot version (1.0) not valid: expecting 1.1.

    The very same happens when loading games stored in VSF format of the classic game compilations "C64 Classix Gold", "C64 Classix Gold II"  and the games delivered with June 2012 "CHIP magazine special edition >>Commodore 64<<"

    Some hints in the documentation and in Google / Forum64 search propose that VICE snapshots are designed for backwards compatibilty. But according to current VICE code this seems not to be the case (major/minor code of snapshot must match exactly, so 1.0 snapshot will not be loaded).

    Is there any chance that old snapshots will work in new versions of VICE ?
    Does a method exist to migrate / convert the version 1.0 snapshots to version 1.1 ?

    Thanks for any hint
    & kind greetings
    codemarvin

     
  • gpz
    gpz
    2012-07-01

    Some hints in the documentation and in Google / Forum64 search propose that VICE snapshots are designed for backwards compatibilty.

    NO. thats a misconception. snapshots contain a state of the internal variables of the emulation, which by principle may change their meaning when something is updated and/or fixed. this can only be "backwards compatible" as long as the emulation itself doesnt change (or at least, doesnt change much), as soon as it does things break.

    But according to current VICE code this seems not to be the case (major/minor code of snapshot must match exactly, so 1.0 snapshot will not be loaded).
    Is there any chance that old snapshots will work in new versions of VICE ? Does a method exist to migrate / convert the version 1.0 snapshots to version 1.1 ?

    no, that'd be an insane task involving to find out (and track, for every version of VICE) what exactly changed since 1.0, what sideeffect each single change has, and then coming up with some magic that fixes the snapshots.

     
  • codemarvin
    codemarvin
    2012-07-11

    Thank you very much gpz for clarification.

     
  • This is really bad. A snapshot should contain the state of the emulated system and not the state of the emulators internals. Many people use snapshots instead of their games internal save functions. I know, it is always possible to switch back to an old version, load the snapshot and do a real save to a savedisk. But this is far from comfortable.

    For the 4 popular C64 Classix CDs mentioned above at least a simple G64 extractor for the VSF files would be enough because the Snapshots contain the games disk image.