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Windows 95 preview disk dump problems

callmejackcallmejack
in Software
I'm trying to dump a set of disks for Windows 95 preview but I have a problem : disk 2-12 have a strange pattern. Is there something wrong with the disks ? or the dump process ? Those are DMF disks.

https://mega.nz/file/TWJS0TYR#6HnOzxoFD9kuiHgEe9vj32BstWKdsYFSDuPawbe5kLY



I also have bad sectors on Disk 1 but there's a dump on archive.org so I can get it from there https://archive.org/details/win95previewprogram_beta3build347_upgrade


Comments

  • ibmpc5150ibmpc5150
    Disk 1 seems to have bad dump, but Disk 2 has no problem.
    Would you please try to dump Disk 1 again.

    Also I'll appreciate it if you can dump another disks.
  • callmejackcallmejack
    So the kind of misaligned tracks are not a real problem ?


    What causes this ?

    Here are additional dumps of disk 1 (SCP and TC) and Disk 3

    https://mega.nz/file/nPQWVZST#VlLKfGqkbik9w9zpQljlIBOZeb1aEUE1SaCSGiph77Y
  • ibmpc5150ibmpc5150
    Thanks. I think your disk 1 seems to be changed as different content.
    So there is no meaning to dump disk 1 anymore.

    Disk 3 dump is good.
    I hope you to dump disk 4 and 5~12
  • SomeGuySomeGuy
    No, they are not a problem since all sectors appear to decode OK.

    On very early 80's disks that were written in low quality belt-driven drives it is very common for tracks to randomly vary in length.

    In this case, however it seems to be very intentional, but I don't see exactly why. On certain tracks there is a larger gap between very specific sectors.

    I'm thinking either the tool they used to master the disk layout had some small issue, or perhaps they went to a lot of trouble to time how long it takes to load the disks and optimize the layout.

    It could be that these gaps coincide with a read buffer size therefore allowing an installer to process data at these points without having to wait for another revolution. But Windows 95 setup reads files from CAB files randomly, so I don't believe the presence/lack of these gaps would make any difference with this specific software. In the case of DMF, the sectors are interleaved anyway so such a small difference should not change anything.

    Curious, but not a problem.
  • callmejackcallmejack
    @SomeGuy thanks very much for the comprehensive explanation :)
  • SomeGuySomeGuy
    Incidentally, it looks like that disk 1 was partially overwritten with some kind of garbage. Like some kind of faulty disk utility wrote a bunch of random junk.
  • ibmpc5150ibmpc5150
    Unlike CDs, it is unequivocal that it is difficult to preserve the contents of floppy disks.
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