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Contents Background A Brief History of Microprocessors Moore's Law Past Efforts to Increase Efficiency The Need for Multicore Multicore Basics Multicore Implementations Intel and AMD Dual-Core Processors CELL Processor Tilera TILE64 Multicore Challenges Power and Temperature Cache Coherence Multithreading Open Issues Improved Memory System System Bus and Interconnection Networks Parallel Programming Starvation Homogeneous vs. Heterogeneous Cores Conclusion

Before multicore processors the performance increase from generation to generation was easy to see, an increase in frequency. This model broke when the high frequencies caused processors to run at speeds that caused increased power consumption and heat dissipation at detrimental levels. Adding multiple cores within a processor gave the solution of running at lower frequencies, but added interesting new problems.

Multicore processors are architected to adhere to reasonable power consumption, heat dissipation, and cache coherence protocols. However, many issues remain unsolved. In order to use a multicore processor at full capacity the applications run on the system must be multithreaded. There are relatively few applications (and more importantly few programmers with the know-how) written with any level of parallelism. The memory systems and interconnection networks also need improvement. And finally, it is still unclear whether homogeneous or heterogeneous cores are more efficient.

Intel's Japanese subsidiary President Kazumasa Yoshida unveils the new processor "Core 2 Duo" Getty Images, Agence France Presse 07-27-2006

With so many different designs (and potential for even more) it is nearly impossible to set any standard for cache coherence, interconnections, and layout. The greatest difficulty remains in teaching parallel programming techniques (since most programmers are so versed in sequential programming) and in redesigning current applications to run optimally on a multicore system.

Multicore processors are an important innovation in the microprocessor timeline. With skilled programmers capable of writing parallelized applications multicore efficiency could be increased dramatically. In years to come we will see much in the way of improvements to these systems. These improvements will provide faster programs and a better computing experience.

© 2008, ProQuest LLC. All rights reserved.

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