5 ms·

Sounds similar to IBM's practice of inserting 'nops' into software of the AS-400s on otherwise identical hardware to create price gradations.

• gwern 16y ago
  But is IBM's practice as easily circumvented? If they are literally inserting nops, then that sounds like something a quick binary conversion could erase.
  • Udo 16y ago
    My assembly-fu is weak, but wouldn't that invalidate all jump addresses and data pointers inside the program?
    • gwern 16y ago
      Yes, but that's not hard to fix either. For example, Google's binary deltas for Chrome updates would be huge if they couldn't easily fix those addresses; see http://dev.chromium.org/developers/design-documents/software-updates-courgette http://dev.chromium.org/developers/design-documents/software...
  • strlen 16y ago
    If you could then update the jump addresses (which are relative to IP) -- definitely possible programmatically, then yes. However, I don't believe you had the permission to alter the system software on an AS400. Not to mention, if you have engineers capable of doing systems programming and re-imaging the system, you're not a target customer for an AS400 or the AS400 is used in such a function where it makes no business sense for you to allocate "real" engineering resources (who are working on your core product, not your accounting system) for this. The AS400 was/is meant to be a turn key solution: IBM profesional services sets it up for you, after which you run SAP (or the like) on it. It also already came with DB2 and is fairly interesting by making the database the file system (decades before WinFS failed, Hans Reiser went to pursue other interests and btrfs is promising but still unstable).
• tibbon 16y ago
  Or maybe better yet, the ways that they kept floppies from being double sided?