TABLE OF CONTENTS Multitasking is another system-design choice that tends to increase processor clock rates. Processor multitasking predates the introduction of microprocessors by at least a decade. Early computers of the 1940s, 1950s, and 1960s were very expensive. Consequently, computer time was also very expensive. One way to distribute the high hardware costs was to give each computer user a share of the computer s time timesharing. Timeshared operating systems started to appear on computers by 1961. Multitasking is timesharing, recast. Multitasking operating systems queue multiple tasks (rather than users) and give each task a time-multiplexed share of the computer. Multitasking makes one processor appear to be doing the work of several. When computers were big and expensive, multitasking made perfect sense.
Initially, microprocessors were also expensive. The first production units of the earliest processor chips cost several hundred dollars throughout the 1970s, so there was significant financial incentive for the expensive processor to execute as many concurrent tasks as possible to amortize the processor s cost across tasks rather than using many expensive processors to implement the multiple tasks. An entire industry has grown up around the development of real-time operating systems for the specific purpose of making microprocessors execute multiple concurrent tasks.
Microprocessor multitasking encourages clock-rate escalation. A faster clock rate allows a processor to execute more concurrent tasks and more complex tasks. As long as processors are expensive, the system-design scales tip toward multitasking because larger power supplies and cooling components (incurred when running...
