Introduction
After more than fours years of secrecy Transmeta finally let the cat - or rather the chip - out of the bag on January 19, 2000. At the elegant Villa Montalvo in Saratoga the company introduced the first two processors of the Crusoe family, processors targeted at mobile Internet applications that will revolutionize the field of mobile computing - at least according to Transmeta.
The company certainly took a new approach to processor design by creating a software-based chip that was specifically developed for combining PC compatibility with performance and low power consumption. It consists of a hardware engine that is logically surrounded by a software layer with the engine being a 128 bit VLIW (very long instruction word) CPU capable of executing up to four operations in each clock cycle. The VLIW's native instruction set bears no resemblance to the x86 instruction set, but the software layer gives x86 programs the impression that they are running on x86 hardware. Transmeta calls this software layer Code Morphing software because it dynamically morphs x86 instructions into VLIW instructions.
In the underlying technology the Transmeta's designers have decoupled the x86 instruction set architecture (ISA) from the processor hardware which allows this hardware to be very different from a conventional x86 implementation. One advantage is that the hardware can be changed radically without affecting legacy x86 software. Each new CPU design only requires modifying the Code Morphing software to translate x86 instructions to the CPU's native instruction set. Fundamentally the Code Morphing software is a dynamic translation system, a program that compiles instructions for an instruction set architecture. It is the only program written directly for the VLIW engine, resides in a ROM and is the first program to start when the processor boots. Even though the chip is able to run any x86 code it does not support SIMD - yet. 'We are working on it', said Transmeta's engineering team at the press conference, 'if we implemented it right now SIMD would consume too much power.'
