3 ms·

The 68851 was more than up to the task, to say nothing of PowerPC chips.

jacquesm 4y ago
That only really happened from the 68030 onward didn't it? Until the 030 processes needed to be pretty careful not to step on each others address space.
- monocasa 4y ago
  It started with the 68020 which came out with 68851 support in an Apple product in 1987. Despite that Mac continued with only partial process protection up until the release of OSX in the early 2000s. My point is their problem wasn't hardware support, but software compatibility.
  - jacquesm 4y ago
    Hm, ok, I wasn't aware that the 020's already had a full MMU on board, thanks for the correction. Probably they made too many assumptions about being able to mess around in other processes address space to enable it by the time they got it.
    - icedchai 4y ago
      I think they are incorrect. The original Mac II (68020 machine) didn't ship with a full MMU. It had a socket for the 68851 though, if one wanted to add one. I somehow doubt many people did. The newer Mac II's (IIx onward) were 68030-based, so they would've had MMUs built in. (They also released the Mac LC later on, which was 68020 based and had no socket for an MMU.)
      - jacquesm 4y ago
        Did the operating system the machine shipped with know what to do with that MMU or was it ignored if installed and only used by alternative os's?
        icedchai 4y ago
        As far as I know, it was ignored until System 7, which added virtual memory support. A/UX (Apple Unix) required it, but that wasn't released until a year or so after the Mac II was initially available.
  - spookthesunset 4y ago
    God I remember those days. The Mac was way late to the party. Was Win95 preemptive or cooperative? I totally forget. Pretty sure only the NT versions of windows were preemptive. I recall there was a period of time when you’d run Windows 2000 because it was so much more stable than 98/ME. It worked mostly okay but it didn’t have as good of support for gaming and was pretty late to the party with DirectX support.
    - burnte 4y ago
      Win95 was both, it didn't preempt Win12 apps, they'd all run in the same VM space, but 32bit ones could be preempted, but still take down the system. Full protetion eeded the NT kernel.
    - twoodfin 4y ago
      Win95 was preemptive and with full memory protection. They obviously had to make compromises for performance and compatibility’s sake that made the long term move to NT essential, but I feel like the Chicago kernel team’s efforts have never (to my knowledge) been well-documented or -appreciated.
      - monocasa 4y ago
        I wouldn't say full memory protection. The shared arena was kind of a "don't touch but the hardware isn't enforcing it" shared 1GB region that all processes had access to.
      - GeekyBear 4y ago
        Definitely not full memory protection. A Win32 program could take down the whole computer.
  - kjs3 4y ago
    Not that Apple used it, but the even earlier 68010+68451 gave you segmented (not paged) memory protection.
  - Maursault 4y ago
    > software compatibility A/UX ran with memory protection on the 68020 Mac II in 1988, probably in 1987 in beta also.
  - icedchai 4y ago
    The Mac II didn't ship with a 68851, however. It was an extra add-on.

That only really happened from the 68030 onward didn't it? Until the 030 processes needed to be pretty careful not to step on each others address space.

monocasa 4y ago
It started with the 68020 which came out with 68851 support in an Apple product in 1987. Despite that Mac continued with only partial process protection up until the release of OSX in the early 2000s. My point is their problem wasn't hardware support, but software compatibility.
- jacquesm 4y ago
  Hm, ok, I wasn't aware that the 020's already had a full MMU on board, thanks for the correction. Probably they made too many assumptions about being able to mess around in other processes address space to enable it by the time they got it.
  - icedchai 4y ago
    I think they are incorrect. The original Mac II (68020 machine) didn't ship with a full MMU. It had a socket for the 68851 though, if one wanted to add one. I somehow doubt many people did. The newer Mac II's (IIx onward) were 68030-based, so they would've had MMUs built in. (They also released the Mac LC later on, which was 68020 based and had no socket for an MMU.)
    - jacquesm 4y ago
      Did the operating system the machine shipped with know what to do with that MMU or was it ignored if installed and only used by alternative os's?
      - icedchai 4y ago
        As far as I know, it was ignored until System 7, which added virtual memory support. A/UX (Apple Unix) required it, but that wasn't released until a year or so after the Mac II was initially available.
- spookthesunset 4y ago
  God I remember those days. The Mac was way late to the party. Was Win95 preemptive or cooperative? I totally forget. Pretty sure only the NT versions of windows were preemptive. I recall there was a period of time when you’d run Windows 2000 because it was so much more stable than 98/ME. It worked mostly okay but it didn’t have as good of support for gaming and was pretty late to the party with DirectX support.
  - burnte 4y ago
    Win95 was both, it didn't preempt Win12 apps, they'd all run in the same VM space, but 32bit ones could be preempted, but still take down the system. Full protetion eeded the NT kernel.
  - twoodfin 4y ago
    Win95 was preemptive and with full memory protection. They obviously had to make compromises for performance and compatibility’s sake that made the long term move to NT essential, but I feel like the Chicago kernel team’s efforts have never (to my knowledge) been well-documented or -appreciated.
    - monocasa 4y ago
      I wouldn't say full memory protection. The shared arena was kind of a "don't touch but the hardware isn't enforcing it" shared 1GB region that all processes had access to.
    - GeekyBear 4y ago
      Definitely not full memory protection. A Win32 program could take down the whole computer.
- kjs3 4y ago
  Not that Apple used it, but the even earlier 68010+68451 gave you segmented (not paged) memory protection.
- Maursault 4y ago
  > software compatibility A/UX ran with memory protection on the 68020 Mac II in 1988, probably in 1987 in beta also.
- icedchai 4y ago
  The Mac II didn't ship with a 68851, however. It was an extra add-on.