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.’
TM3120
According to Transmeta the first two Crusoe models, the TM3120 and TM5400, were designed for minimal space and power consumption. By eliminating roughly 75 % of the logic transistors that would be required for an all-hardware design of similar performance, it was also possible to reduce the die size of the chip and thus the power dissipation. The difference is quite substantial: at comparable clock frequencies without active cooling a Pentium III sizzles at 105 C (221 F) when playing a DVD, the TM5400 only reaches 48 C (118 F). Another feature of the TM5400 is a power-saving technology called LongRun: it allows the TM5400 to adjust its power consumption without turning itself off but by adjusting its clock frequency on the fly.
Targeted at Web pads and mobile clients the TM3120 features 96 KB of L1 cache, a die size of 77 mmІ and runs Mobile Linux in ROM. It is immediately available costing $65 for the 333 MHz and $89 for the 400 MHz version. The TM5400 is sampling and is supposed to be shipping by mid 2000. It comes with 128 KB L1 cache, 256 KB L2 cache, runs Microsoft Windows and NT, is aimed at ultra-light mobile PCs and costs $119 for the 500 MHz and $329 for the 700 MHz version. The die size is 73 mmІ. Both processors have an integrated Northbridge. As a fabless semiconductor company Transmeta needed a manufacturing partner: IBM produces the chips in 0.22 and possibly 0.18-micron technology, respectively. Transmeta has no plans to license the core or to open source the Code Morphing software. The company is selling to OEMs and system manufacturers directly.
TM5400
At the press conference Transmeta would not disclose any partners and instead showed reference designs that were developed in-house. So far none of the big system houses has officially stepped forward and revealed they are building devices based on the Crusoe chips. However, attendees with nametags from Sony, NEC, Hewlett-Packard, S3 and Visual Technology were seen at the launch. A day after the event S3 announced they are planning to build Linux-based Internet appliances using Crusoe. S3 produces for example the Rio Internet audio player.
