Age

CRC wrote: The Lisa's multitasking was real enough, but misinformation about it has gotten out of hand. Most people now claim that it used preemptive multitasking, while in fact the OS was very deliberately designed to use cooperative multitasking. Bruce Daniels, author of the Lisa OS, explained the choice in the paper "Architecture of the Lisa Personal Computer" in the March 1984 issue of Proceedings of the IEEE: The CPU is multiplexed among the runnable processes by using a priority based nonpreemptive scheduling algorithm. This nonpreemptive scheduling policy guarantees correct access to shared resources, such as the bit-mapped display, by interactive processes without the performance penalty of having to explicitly lock and unlock these resources for each access. Eric