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Chapter 1. Hardware, Processes, and Thre... > The Motivation for Multicore Process...

The Motivation for Multicore Processors

Microprocessors have been around for a long time. The x86 architecture has roots going back to the 8086, which was released in 1978. The SPARC architecture is more recent, with the first SPARC processor being available in 1987. Over much of that time performance gains have come from increases in processor clock speed (the original 8086 processor ran at about 5MHz, and the latest is greater than 3GHz, about a 600× increase in frequency) and architecture improvements (issuing multiple instructions at the same time, and so on). However, recent processors have increased the number of cores on the chip rather than emphasizing gains in the performance of a single thread running on the processor. The core of a processor is the part that executes the instructions in an application, so having multiple cores enables a single processor to simultaneously execute multiple applications.

The reason for the change to multicore processors is easy to understand. It has become increasingly hard to improve serial performance. It takes large amounts of area on the silicon to enable the processor to execute instructions faster, and doing so increases the amount of power consumed and heat generated. The performance gains obtained through this approach are sometimes impressive, but more often they are relatively modest gains of 10% to 20%. In contrast, rather than using this area of silicon to increase single-threaded performance, using it to add an additional core produces a processor that has the potential to do twice the amount of work; a processor that has four cores might achieve four times the work. So, the most effective way of improving overall performance is to increase the number of threads that the processor can support. Obviously, utilizing multiple cores becomes a software problem rather than a hardware problem, but as will be discussed in this book, this is a well-studied software problem.


  

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