PC Floppy Copy Protection: Xemag Xelok

(martypc.blogspot.com)

9 points | by GloriousCow 14 hours ago ago

5 comments

  • somat 10 hours ago ago

    Probably a silly question. but are those images of a disks layout high enough resolution to recreate the disk?

    I know it's silly because if you wanted to encode a disk image such that it works as a png you would not use a circular layout. Too many weird angles, it would make it harder than it needs to be to reconstruct.

    • GloriousCow 9 hours ago ago

      For the ones that I make to look pretty, the data is colored in buckets of 8 bits, using the bit-count per byte to select a shade in 8 steps from 0-255. So there's at least 8 times less data than you would need. Then it is downsampled 4x to get nice antialiasing, so that is more data loss.

      I do have a bit-mode, and if you rendered at high enough resolution you could do it, maybe something like 32k x 32k. But this is a very inefficient way to store a disk image. :)

  • GloriousCow 14 hours ago ago

    In this post in a series on PC copy floppy protections, we take a look at XEMAG duplication's "Xelok" scheme.

    Xelok was quite devious on the Apple II, implementing "fat tracks" that could not be produced with a conventional disk drive. However the PC doesn't allow such tricks, so Xelok appears a bit different on the PC platform.

    We take a look at two titles that use it, Sargon III and The Ancient Art of War.

    We also take note of a rather amusing bypass for this protection!

  • ksaj 14 hours ago ago

    I find it humourous that their logo looks like what happens when older generations of Windows failed on popups.