You are getting your versions muddled up.
replyYou are describing attributes of the NeXT-based OS X but calling it MacOS 9.
MacOS 9 was the final version of Classic. No preemption, weak virtual memory, weak cooperative multitasking, no virtual machines for anything.
MacOS 9 is the OS that ran inside the Blue Box on Mac OS X for backwards compatibility.
> You are describing attributes of the NeXT-based OS X but calling it MacOS 9.
replyYou're mistaken.
> MacOS 9 [had] no preemption
Classic Mac OS has had vertical retrace (VBL) interrupts since System 1.0 (which are a form of preemption). But suppose we disregard that.
>> MacOS 9 had a preemptively scheduled kernel.
The GP is correct. Applications run cooperatively within the Blue task, but the Blue task itself runs preemptively with other MP tasks (which an application can create).