Cruising with Crusoe

Transmeta–the company formed by Paul Allen, the company that had Linus Torvalds of Linux fame as its most famous employee, and the company that had everyone guessing on what they were up to–has finally taken the covers off. Transmeta’s product is the Crusoe processor, targeted at Internet and mobile computing appliances.

Two variants of the Crusoe have been introduced so far–the TM 3120 which is currently available, and the TM 5400, which is in the sampling stage, and is expected to go into production by the middle of this year.

The TM 3120 is available in ranges of 333-400 MHz, and has an L1 cache of 96 kB. It supports 66-133 MHz SDRAM. The TM 5400 will be available in ranges of 500-700 MHz, with 128 kB L1 cache, and 256 kB L2 cache. The 5400 will support 100-166 MHz DDR-SDRAM main memory and upgrade memory of 66-133 MHz SDRAM. 

The Crusoe has made innovations in processor technology by replacing hardware components with software. This makes them lighter, less prone to heating, and less power-hungry than traditional mobile processors. In idle mode, the TM 3120 operates at a power of 20 milliwatts, while the TM 5400 operates on 8 milliwatts. The processor is compatible with x86 operating systems, including Linux, and runs Internet plug-ins written for the x86. Transmeta “expects “ that Linux will be the primary operating system for mobile Internet devices and has parallely developed Mobile Linux for that purpose, with enhancements in power management and reduction in memory footprint.

The hardware component is a VLIW (Very Long Instruction Word) engine, which has no resemblance to instruction sets of x86 processors. This is surrounded by a software layer, called Code Morphing software which dynamically translates x86 instructions into the hardware’s native instruction set. The software translates blocks of x86 instructions once, and saves the translation in a translation cache. The next time the code is required, the system doesn’t translate it again–it only executes the translated code. This means that the Crusoe uses less transistors than conventional processors but is as fast or faster.

In addition, the TM 5400 has another power-saving feature. The software can continuously monitor the demands made on the processor by the application it’s running, and adjust its voltage and clock frequency accordingly. That is, if a particular application doesn’t need the processor to run at maximum speed, the software cuts back the frequency and voltage of the processor to cut back speed, thereby reducing power consumption. In contrast, most conventional CPUs regulate power consumption by rapidly alternating between running the processor at full speed and turning it off completely. 

Transmeta claims that both processors are powerful enough to run the full range of applications–office suites, Web browsers, e-mail applications, Internet content playback, multimedia applications such as DVDs, etc, on mobile platforms.