Single and Multiprocessor Applications

The goal of a multiprocessor is to raise the computing power when compared to a uniprocessor. The issue is having correct programs written to take advantage of multiprocessor or multicore multiprocessors. A reason as to why programs need to be written correctly to get better performance is because “otherwise, you would just use a sequential program on a uniprocessor, as sequential programming is simpler” (Patterson & Hennessy, 2014, sect. 6.2). If a program is not designed to take advantage of a multiprocessor, then it runs as a sequential program for a uniprocessor. Multiprocessors are mainly considered a shared memory multiprocessor (SMP) because it “shares a single physical address space” (Patterson & Hennessy, 2014, sect. 6.1).

A real-world example of how an application developed for a uniprocessor can impact the performance of executing the same application on a multiprocessor architecture is within different Windows operating systems. Early versions of Windows had different kernel versions depending on if it was a uniprocessor or multiprocessor (Soloman, Russinovich, & Ionescu, 2007). The reasoning was to know which programs to run with a multiprocessor system versus a uniprocessor system. Soloman, Russinovich, and Ionescu (2007) explain this as “the majority of systems currently sold include at least two cores and because the few uniprocessor-only optimizations result in negligible performance improvement” (p. 41). With this example, an application that was made for a uniprocessor system being run on a multiprocessor system resulted in poor performance. That is why in older versions of Windows with two kernels were needed to differentiate how many CPUs the computer had.

References

Patterson, D. A., & Hennessy, J. L. (2014). Computer organization and design: The hardware/software interface (5th ed.). Retrieved from https://zybooks.zyante.com/

Soloman, D. A., Russinovich, M. E., & Ionescu, A. (2007). Windows Internals. Retrieved 9 December, 2021, from https://books.google.com/books

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