CPU Architecture and the Fetch–Decode–Execute Cycle: Question 10
Syllabus 3.1
A manufacturer is designing a digital kitchen scale. It only needs to measure weight, display the reading, and let the user zero the scale. The manufacturer is choosing between two options: building the scale around a small, dedicated embedded microprocessor that runs one fixed program, or building it around a general purpose computer chip capable of running a full operating system and multiple apps.
(a) State and explain two advantages that the dedicated embedded microprocessor option would most likely offer the manufacturer for this kitchen scale, compared with the general purpose computer chip option. [4]
(b) State one advantage that the general purpose computer chip option would offer instead. [1]
(c) Explain one disadvantage, in the context of this simple kitchen scale, of using a general purpose computer chip instead of the dedicated embedded microprocessor. [2]
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Worked solution
Part (a): Advantages of the dedicated embedded microprocessor
- Lower power consumption. The embedded microprocessor has only one fixed program to run, reading the sensor, doing the weight calculation and updating the display, with no operating system or background apps competing for power. This lets the scale run for a long time on small batteries. [2]
- Higher reliability. Because the microprocessor can only ever execute the single, fixed weighing program, there is no possibility of an unrelated app crashing, a background update failing, or unnecessary software interfering with its one job, making unexpected failures far less likely than on a chip running a full operating system with many programs. [2]
Part (b): An advantage of the general purpose computer chip
A general purpose computer chip is not restricted to one fixed program, so the scale could later run additional or updated software. For example, a companion app that logs nutrition data or connects to Wi-Fi. Something the dedicated embedded microprocessor’s fixed program could never be extended to do.
Part (c): A disadvantage of the general purpose computer chip, in this context
Running a full operating system and supporting multiple background processes takes far more electrical power than simply reading a sensor and updating a display. [1] For a device that only needs to perform one simple task, this extra power draw would drain the scale’s batteries much faster than the dedicated embedded microprocessor would, without giving the user any real benefit for the weighing task itself. [1]
Final answers
- (a) Lower power consumption (no operating system or background apps to power) and higher reliability (only ever running the one fixed weighing program).
- (b) The ability to run additional or updated software in the future.
- (c) It would draw far more power than the simple weighing task requires, draining the battery faster for no real benefit.