> There is a footnote about Amiga offering preemptive multitasking 7 years earlier.
The thing is, that's only part of the story.
There's a generation of techies who are about 40 now who don't remember this stuff well, and some of the older ones have forgotten with time but don't realise. I had some greybeard angrily telling me that floppy drives were IDE recently. Senile idiot.
Anyway.
Preemptive multitasking is only part of the story. Lots of systems had it. Windows 2.0 could do preemptive multitasking -- but only of DOS apps, and only in the base 640kB of RAM, so it was pretty useless.
It sounds good but it's not. Because the other key ingredient is memory protection. You need both, together, to have a compelling deal. Amiga and Windows 2.x/3.x only had the preemption part, they had no hardware memory management or protection to go with it. (Windows 3.x when running on a 386 and also when given >2MB RAM could do some, for DOS apps, but not much.)
Having multiple pre-emptive tasks is relatively easy if they are all in the same memory space, but it's horribly horribly unstable.
Also see: microkernels. In size terms, AmigaOS was a microkernel, but a microkernel without memory protection is not such a big deal, because the hard part of a microkernel is the interprocess communication, and if they can just do that by reading and writing each other's RAM it's trivially easy but also trivially insecure and trivially unstable.
RISC OS had pre-emptive multitasking too... but only of text-only command-line windows, and there were few CLI RISC OS apps so it was mostly useless. At least on 16-bit Windows there were lots of DOS apps so it was vaguely useful, if they'd fit into memory. Which only trivial ones would. Windows 3 came along very late in the DOS era, and by then, most DOS apps didn't fit into memory on their own one at a time. I made good money optimising DOS memory around 1990-1992 because I was very good at it and without it most DOS apps didn't fit into 500-550kB any more. So two of them in 640kB? Forget it.
Preemption is clever. It lets apps that weren't designed to multitask do it.
But it's also slow. Which is why RISC OS didn't do it. Co-op is much quicker
which is also why OSes like RISC OS and 16-bit Windows chose it for their GUI apps: because GUI apps strained the resources of late-1980s/very-early-1990s computers. So you had 2 choices:
• The Mac and GEM way: don't multitask at all.
• The 16-bit Windows and RISC OS way: multitask cooperatively, and hope nothing goes wrong.
Later, notably, MacOS 7-8-9 and Falcon MultiTOS/MiNT/MagiC etc added coop multitasking to single-tasking GUI OSes. I used MacOS 8.x and 9.x a lot and I really liked them. They were extraordinarily usable to an extent Mac OS X has never and will never catch up with.
But the good thing about owning a Mac in the 1990s was that at least one thing in your life was guaranteed to go down on you every single day.
The thing is, that's only part of the story.
There's a generation of techies who are about 40 now who don't remember this stuff well, and some of the older ones have forgotten with time but don't realise. I had some greybeard angrily telling me that floppy drives were IDE recently. Senile idiot.
Anyway.
Preemptive multitasking is only part of the story. Lots of systems had it. Windows 2.0 could do preemptive multitasking -- but only of DOS apps, and only in the base 640kB of RAM, so it was pretty useless.
It sounds good but it's not. Because the other key ingredient is memory protection. You need both, together, to have a compelling deal. Amiga and Windows 2.x/3.x only had the preemption part, they had no hardware memory management or protection to go with it. (Windows 3.x when running on a 386 and also when given >2MB RAM could do some, for DOS apps, but not much.)
Having multiple pre-emptive tasks is relatively easy if they are all in the same memory space, but it's horribly horribly unstable.
Also see: microkernels. In size terms, AmigaOS was a microkernel, but a microkernel without memory protection is not such a big deal, because the hard part of a microkernel is the interprocess communication, and if they can just do that by reading and writing each other's RAM it's trivially easy but also trivially insecure and trivially unstable.
RISC OS had pre-emptive multitasking too... but only of text-only command-line windows, and there were few CLI RISC OS apps so it was mostly useless. At least on 16-bit Windows there were lots of DOS apps so it was vaguely useful, if they'd fit into memory. Which only trivial ones would. Windows 3 came along very late in the DOS era, and by then, most DOS apps didn't fit into memory on their own one at a time. I made good money optimising DOS memory around 1990-1992 because I was very good at it and without it most DOS apps didn't fit into 500-550kB any more. So two of them in 640kB? Forget it.
Preemption is clever. It lets apps that weren't designed to multitask do it.
But it's also slow. Which is why RISC OS didn't do it. Co-op is much quicker which is also why OSes like RISC OS and 16-bit Windows chose it for their GUI apps: because GUI apps strained the resources of late-1980s/very-early-1990s computers. So you had 2 choices:
• The Mac and GEM way: don't multitask at all.
• The 16-bit Windows and RISC OS way: multitask cooperatively, and hope nothing goes wrong.
Later, notably, MacOS 7-8-9 and Falcon MultiTOS/MiNT/MagiC etc added coop multitasking to single-tasking GUI OSes. I used MacOS 8.x and 9.x a lot and I really liked them. They were extraordinarily usable to an extent Mac OS X has never and will never catch up with.
But the good thing about owning a Mac in the 1990s was that at least one thing in your life was guaranteed to go down on you every single day.