Crusoe Processor

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1. INTRODUCTION

Mobile computing has been the buzzword for quite a long time. Mobile computing devices like laptops, webslates & notebook PCs are becoming common nowadays. The heart of every PC whether a desktop or mobile PC is the microprocessor. Several microprocessors are available in the market for desktop PCs from companies like Intel, AMD, Cyrix etc.The mobile computing market has never had a microprocessor specifically designed for it. The microprocessors used in mobile PCs are optimized versions of the desktop PC microprocessor. Mobile computing makes very different demands on processors than desktop computing, yet up until now, mobile x86 platforms have simply made do with the same old processors originally designed for desktops. Those processors consume lots of power, and they get very hot. When you're on the go, a power-hungry processor means you have to pay a price: run out of power before you've finished, run more slowly and lose application performance, or run through the airport with pounds of extra batteries. A hot processor also needs fans to cool it; making the resulting mobile computer bigger, clunkier and noisier. A newly designed microprocessor with low power consumption will still be rejected by the market if the performance is poor. So any attempt in this regard must have a proper 'performance-power' balance to ensure commercial success. A newly designed microprocessor must be fully x86 compatible that is they should run x86 applications just like conventional x86 microprocessors since most of the presently available software’s have been designed to work on x86 platform. Crusoe is the new microprocessor which has been designed specially for the mobile computing market. It has been designed after considering the above mentioned constraints. This microprocessor was developed by a small Silicon Valley startup company called Transmeta Corp. after five years of secret toil at an expenditure of $100 million. The concept of Crusoe is well understood from the simple sketch of the processor architecture, called 'amoeba’. In this concept, the x86-architecture is an ill-defined amoeba containing features like segmentation, ASCII arithmetic, variable-length instructions etc. The amoeba explained how a traditional microprocessor was, in their design, to be divided up into hardware and software.

Thus Crusoe was conceptualized as a hybrid microprocessor that is it has a software part and a hardware part with the software layer surrounding the hardware unit. The role of software is to act as an emulator to translate x86 binaries into native code at run time. Crusoe is a 128-bit microprocessor fabricated using the CMOS process. The chip's design is based on a technique called VLIW to ensure design simplicity and high performance. Besides this it also uses Transmeta's two patented technologies, namely, Code Morphing Software and Longrun Power Management. It is a highly integrated processor available in different versions for different market segments.

Technology Perspective
The Transmeta designers have decoupled the x86 instruction set architecture (ISA) from the underlying processor hardware, which allows this hardware to be very different from a conventional x86 implementation. For the same reason, the underlying hardware can be changed radically without affecting legacy x86 software: each new CPU design only requires a new version of the Code Morphing software to translate x86 instructions to the new CPU’s native instruction set. For the initial Transmeta products, models TM3120 and TM5400, the hardware designers opted for minimal space and power. By eliminating roughly three quarters of the logic transistors that would be required for an all-hardware design of similar performance, the designers have likewise reduced power requirements and die size. However, future hardware designs can emphasize different factors and accordingly use different implementation techniques. Finally, the Code...
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