Transmeta's Crusoe
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Authors
Authors: Ravi Madapati
Faculty Member
ICMR (IBS Center for Management Research).
Links
Tools
Crusoe Contd...
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Crusoe reduced power consumption by transferring the most complex part of a processor's job- determining what instructions to execute and when-to software in a process called Code Morphing4. The significantly reduced number of transistors led to a very small die size that was not only economical to build but also lowered power consumption. Even for heavy-duty multimedia applications like DVD, the processor typically consumed just 1-2 watts. The Code Morphing software acted as a 'shell' that surrounded the hardware core and translated x86 instructions into native Crusoe instructions. In addition, this software contained a dynamic compiler and code optimizer, to identify blocks of software that made up the repetitive sequences commonly found in applications, and reduced them to a smaller set of executable instructions. |
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Likewise, decoupling the hardware design from the system and application software allowed hardware designers to evolve (or eventually replace) their designs without interfering with the legacy software base. Transmeta believed that Intel and AMD mobile processors were really desktop processors that had been de-rated for the mobile market. As such, they incorporated several generations of increasingly burdensome hardware complexity. While these processors had been the driving force behind desktop computing since the 1970s, they had shown their limitations in mobile computers where trade-offs between performance, excessive heat, and battery life were important.
Transmeta believed that its Code Morphing technology had changed the entire approach to designing microprocessors. Transmeta had dramatically expanded the design space that microprocessor designers could explore for optimum solutions. As a result, microprocessor development teams enlisted software experts and expertise, working largely in parallel with hardware engineers to bring products to market faster. Upgrades to the software portion of a microprocessor could be rolled-out independently from the chip. The Code Morphing software itself offered opportunities to improve performance without altering the underlying hardware. Transmeta believed that this system was a first-generation embodiment of a new technology that could be further optimized with experience and experimentation. Because the Code Morphing software typically Flash ROMs5 on the motherboard, improved versions could even be downloaded into processors in the field.
4] The Code Morphing software was designed to dynamically translate x86 instructions into VLIW (Very Long Instruction Word) instructions for the underlying Crusoe hardware engine. The Code Morphing software resided in flash ROM and was the first application to launch when the Crusoe processor is powered up. Upon completion of its initialization, other system software components such as the operating system were loaded in traditional fashion.
5] ROM (Read Only Memory): Pronounced 'rahm', acronym for read-only memory, computer memory on which data has been pre-recorded. Once data has been written onto a ROM chip, it cannot be removed and can only be read. Unlike main memory (RAM), ROM retains its contents even when the computer is turned off. ROM is referred to as being non-volatile, whereas RAM is volatile. Most personal computers contain a small amount of ROM that stores critical programs such as the program that boots the computer. In addition, ROMs are used extensively in calculators and peripheral devices such as laser printers, whose fonts are often stored in ROMs.