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For those wondering what software depended on A20 wraparound, there is this interesting series of articles: https://www.os2museum.com/wp/who-needs-the-address-

For those wondering what software depended on A20 wraparound, there is this interesting series of articles: https://www.os2museum.com/wp/who-needs-the-address-wraparound-anyway/ https://www.os2museum.com/wp/who-needs-the-address-wraparoun... https://www.os2museum.com/wp/the-a20-gate-it-wasnt-wordstar/ https://www.os2museum.com/wp/the-a20-gate-it-wasnt-wordstar/ https://www.os2museum.com/wp/exepack-and-the-a20-gate/ https://www.os2museum.com/wp/exepack-and-the-a20-gate/ https://www.os2museum.com/wp/the-a20-gate-fallout/ https://www.os2museum.com/wp/the-a20-gate-fallout/

bigstrat2003 1y ago
It's always blown my mind that software would depend on that behavior. What possessed people to do that? It's very obviously a bad idea.
- toast0 1y ago
  If the system behavior is defined to wrap around, using defined system behavior to reduce code complexity makes perfect sense. This was in an era where new computer systems usually meant throwing away all the existing software and rewriting it (or doing a fresh port anyway). Why would you assume someone would extend the system and cause trouble.
- rasz 1y ago
  Im blown away at how small a number of software depended on the wraparound and IBM still forced A20 hack on us all.