Acknowledgements

First and foremost, I thank Pat and Shaina, my wife and daughter, for putting up with me once more while I write yet another book.

Next, I thank Steve Roddy who originally conceived of this book and for allowing me the time to write it.

Thanks to the entire team at Tensilica for making a new way to design SOCs possible in the first place. A large number of people have contributed to Tensilica’s ability to revolutionize SOC design. First and foremost is Chris Rowen who is Tensilica’s founder, CEO, and president. Rowen has been involved with RISC microprocessors essentially since day one. He was a graduate student under John Hennesy during the early academic development of the MIPS-I RISC microprocessor at Stanford and he went on to become one of the founders of MIPS Technologies, the company that commercialized the MIPS processor architecture.

From this very deep understanding of RISC architectures and of the growing use of such architectures in SOCs, Rowen developed the idea of a post-RISC, configurable microprocessor core that took advantage of rapidly evolving silicon fabrication technology in ways that no fixed-ISA processor cores can. Rowen’s ideas evolved into the Xtensa architecture at Tensilica. Many of the ideas and charts that appear in this book originated with him.

Over the next several years, the dozens of members of Tensilica’s engineering group have augmented Rowen’s initial idea with a huge number of groundbreaking hardware architecture and software contributions. Hardware innovations include the TIE (Tensilica Instruction Extension) language, the FLIX (flexible-length instruction extensions) VLIW (very-long instruction word)-like extensions that give processors the ability to execute multiple independent operations per instruction without VLIW code bloat, and bottleneck-breaking ports and queues. Software innovations include the automatic configuration of entire software-development tool sets from TIE descriptions, fast vectorizing compilers, and fast instruction-set simulators. Without the configurable Xtensa processor, system designers would still be in the Stone Age.

Special thanks to Stuart Fiske for checking and correcting all of my cache-interface diagrams, to Paula Jones for acting as my copy editor (everyone needs a good editor), and to Tomo Tohara for working up the H.264 video decoder block diagram in Chapter 2.

Also, special thanks to my first readers. Besides Paula Jones, these include: Max Baron, Marcus Binning, and Grant Martin. Grant has been a real mentor to me and has taught me a lot about writing books in the last 2 years.

Thanks to photographic and multimedia artist extraordinaire Steve Emery who created a dynamite cover for this book. Believe it or not, I found him on eBay!

And finally, thanks to Chuck Glaser at Elsevier, whose enthusiasm for the book made sure the project advanced when nothing else would.