Multi-tasking really wasn't a thing on PCs much before 1988; I mean, you could do it, if you had a bottomless pit of money with which to buy RAM by the half-megabyte and a 286-class processor and a memory manager like DesqView or a penchant for paying DR big ticket license fees for Concurrent CP/M-86, but otherwise ...?

Time telescopes our memories.

Ahem, the Amiga would like a word...

The 68000 hardware could support preemptive multitasking just fine; what it lacked was a hardware MMU. You couldn't run an OS with protected virtual memory on a 68000 without external hardware support (sometimes another 68000 was used for this!). Accordingly, all tasks on the Amiga had access to each other's memory space and even the kernel's. But the fact that Switcher, MultiFinder, and later versions of Mac OS could only support cooperative multitasking was more a Mac OS limitation than a hardware one.

Yes, exactly. Thanks for clarifying. As you say, the lack of preemptive multitasking was mainly an OS limitation, although a hardware MMU would have really helped. I remember at the time reading about the hoops that Andy had to go through to get Switcher (which, as mentioned in other replies, became MultiFinder) to work. One of the issues was that the single app OS model used a bunch of low memory locations as system globals...on every context switch these had to be saved and restored because each running application could change them. (ouch!)