SAN FRANCISCO (03/06/2000) - For almost five years, Transmeta Corp. has been a Silicon Valley enigma. The well-funded start-up firm said virtually nothing about its product plans. But in January the company lifted the veil on two innovative, low power microprocessors for notebook PCs and Web appliances. If Transmeta keeps its promises, you'll soon be seeing some very interesting machines.
Transmeta's new line, code-named Crusoe, begins with the TM3120, a chip designed to fuel the emerging category of Web tablets--inexpensive Net-access devices. Not surprisingly, since Linux developer Linus Torvalds is an employee, Transmeta has also developed a mobile version of that OS. Transmeta-based Web tablets, running at about 400 MHz, should appear soon: S3's Diamond Multimedia group plans to ship a product by midyear.
The Transmeta 700-MHz TM5400 will power thin and light notebook PCs with exceptional battery life--one benefit of Transmeta's radical approach to CPU design.
The Design Secret
Rather than design a chip like Intel's Pentium III or AMD's Athlon that directly executes x86 instructions, Transmeta created a very-long-instruction word processor. Code-morphing software translates x86 instructions into the VLIW chip's instruction set. From the PC user's perspective, a Transmeta chip is simply an x86 chip that runs today's standard applications. But from the processor designer's and manufacturer's perspectives, this approach has several advantages.
The complexity of the x86 instruction set is shifted to software, allowing the chip to remain small, which reduces cost and power consumption. This approach also lets Transmeta improve its instruction set later, while retaining compatibility with existing apps.
Software translation isn't a new idea, but prior products have been plagued by poor performance. Transmeta's design emphasizes quick, efficient software translation. Some speed is sacrificed, but the company claims that its 700-MHz chip will perform at least as well as a PIII-500.
The Crusoe CPUs will use far less power than their peers. Transmeta says its chips will consume only 1 to 2 watts, compared with 8 to 16 watts for other mobile x86 processors in the same performance range. The simpler microprocessor core helps, as does an integrated DRAM controller and PCI bus interface.
Perhaps most notably, the chip uses an advanced form of power management that Transmeta calls LongRun.
Low, Low Power
Like Intel's SpeedStep technology, used in the recently launched mobile Pentium-III chips, LongRun reduces the chip's power-supply voltage and its clock frequency to cut power consumption--but in a much more sophisticated way.
SpeedStep has two modes, low power and high performance, and it switches from one to the other based on whether AC power is available (unless the user intervenes). LongRun dynamically chooses among as many as 16 voltage and speed levels.
The code-morphing software helps determine how much performance is needed. When you work in an e-mail program, for example, the processor is usually simply waiting for you to press a key, so the Crusoe automatically drops to its lowest voltage and speed during this time. When you play a DVD movie, a relatively demanding task, the processor moves to a higher power level. Transmeta's power advantage will translate into longer battery life, systems without fans, and lighter systems with smaller batteries.
Unlike AMD, which is trying to challenge Intel across the breadth of the PC market, Transmeta has picked a market segment--low power--where its technology promises a dramatic advantage. If all goes well, the all-day notebook should arrive this fall.
Michael Slater (firstname.lastname@example.org) is founder and principal analyst at Cahners MicroDesign Resources (www.mdronline.com), where he serves as executive editor of Microprocessor Report.