Apr 15, 2021 1:10:25 PM tom ehlert <t...@drivesnapshot.de>:
>you probably meant 'OS architecture' (not CPU). Nope, I meant CPU. You start out with an unprotected CPU architecture like the 8086. The OS is basically just a set of hardware access libraries that applications can use or not as they wish (as they have direct access to the hardware). When a protected architecture like is the 386 is introduced (the 286, of course, didn't have a way of running 8086 code with protection enabled) it immediately opens up this can of worms, because back compatibility with applications that access the hardware directly often requires that they continue to be allowed hardware access, while system stability with multiple legacy OS instances running tends to demand that they not be allowed hardware access. So there is inevitably an incremental transition process, rather than an immediate snapover to a fully protected environment. The PC wasn't the only hardware platform and DOS wasn't the only OS that this happened to. Of course, talking about this process in the present tense, as if it's something that still happens today, may not be the best, as any unprotected architecture introduced with modern transistor budgets likely has a specific purpose like hard realtime and will never see a transition to a protected architecture, and any general-purpose architecture introduced today is almost certain to have memory protection. _______________________________________________ Freedos-user mailing list Freedos-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freedos-user
