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Thread: DOS Floppy Disk checker

  1. #21
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    I completely forgot about changing the interleave. That lets you put "sector 1" anywhere physically on the track. Thanks for the explanation.

    And yes, that's horrible.
    Offering a bounty for:
    - The software "Overhead Express" (doesn't have to be original, can be a copy)
    - A working Sanyo MBC-775, Olivetti M24, or Logabax 1600
    - Documentation and original disks for: Panasonic Sr. Partner, Zenith Z-160 series
    - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)

  2. #22
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    In theory, there's no BIOS restriction on what you can put in sector headers, so you could even have 18 copies of sector 1; write all of them and hope that one works.

    I've never understood the reason for putting critical structures on the first track of a disk--the place where the heads get positioned when a drive is started. Most 8" floppies that use the IBM 3740 convention use the first track for VTOC and HDR information only.

  3. #23
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    Apple DOS put the catalog on track 17; C64 put it on track 18. What other disk formats put more sensitive information in the middle of the disk, rather than either end?
    Offering a bounty for:
    - The software "Overhead Express" (doesn't have to be original, can be a copy)
    - A working Sanyo MBC-775, Olivetti M24, or Logabax 1600
    - Documentation and original disks for: Panasonic Sr. Partner, Zenith Z-160 series
    - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)

  4. #24
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    Most CP/M formats put the boot tracks on the first part of the disk, followed by the directory. There is at least one (National BLC 86/12) that plunks the directory down on cylinder 39. ISIS reserves the first track (always FM in the 8 inch version). There are other examples.

    The benefit of keeping the FAT off the first track, of course, is that if you lose the first track, you still have all of your files.

    I believe that Apple HFS keeps a copy of the allocation information on the last cylinder as well.

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