Not entirely sure why co-operative multi-tasking has any significantly less overheads than pre-emptive. Each of these OSs had to make different sets of compromises based on the hardware costs — and there wasn’t really an MMU for the 68k until much later into its life unless you were prepared to design your own (eg. as Apple did with Lisa)
The Arm base acorn range did have something (memory stretch for the detail) but it’s RISC OS made a different set of compromises for other reasons.
I remember an article in Byte (I think; might’ve been PCW) comparing the architecture of the Amiga vs MacOS and how the Mac offloaded an awful lot of the work of a gui app onto the programmer vs the Amiga OS; certainly the Amiga mapped onto the 'state of the art' OS design I had recently learnt in college at the time with message passing etc..
Anyway, I think — similar to your description in another article about OS design being locked into the UNIX-like architecture, MMU and context switch support are similarly locked in with basically a supervisor/user security boundary (although newer have a couple more for hypervisor and so on) and tying virtual memory paging mechanisms tightly with security permissions; there’s no room to innovate system software without overhead.
![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png)
timeasmymeasure
no subject
Date: 2024-04-02 12:59 pm (UTC)The Arm base acorn range did have something (memory stretch for the detail) but it’s RISC OS made a different set of compromises for other reasons.
I remember an article in Byte (I think; might’ve been PCW) comparing the architecture of the Amiga vs MacOS and how the Mac offloaded an awful lot of the work of a gui app onto the programmer vs the Amiga OS; certainly the Amiga mapped onto the 'state of the art' OS design I had recently learnt in college at the time with message passing etc..
Anyway, I think — similar to your description in another article about OS design being locked into the UNIX-like architecture, MMU and context switch support are similarly locked in with basically a supervisor/user security boundary (although newer have a couple more for hypervisor and so on) and tying virtual memory paging mechanisms tightly with security permissions; there’s no room to innovate system software without overhead.