Before Ditzel founded Transmeta, translation techniques had been used only to make existing, noncompatible software and hardware speak to one another. Ditzel and his co-founders made an intellectual leap: If an additional layer of software could make applications run on noncompatible hardware, what was to stop them from making radical changes in the underlying hardware itself, taking advantage of the latest capabilities?
In 1994, Ditzel and co-founder Doug Laird were both coming off a project at Sun designed to make Windows run better on Sun workstations, using dynamic binary translation techniques. “We realized that if we could just add some features to the hardware, we could actually make this thing go pretty fast,” says Laird. “It was a cool idea,” he adds, recalling that Sun wasn’t interested in changing its processor design to make it better at running applications that had been written to run on standard Intel chips. Ditzel and Laird struck out on their own. Ditzel recruited Colin Hunter, a respected expert in emulation techniques, and Robert Cmelik, who had been doing work in code optimization at Sun.
As is often the case in technology innovation, practice proved harder than theory: Transmeta’s first chip design ran so slowly that it took the chip half an hour just to boot the operating system. But with each of four chip revisions, the team learned more about binary translation. Five years of painstaking work-performed by a brigade of 200 engineers backed by several hundred million dollars of venture capital-produced a chip that ran fast enough to compare favorably with Intel processors. In January of this year, Transmeta announced the first two hybrid silicon/software chips in the Crusoe line. The first, called TM5400, is a 700-megahertz chip for the ultrathin, ultralight Windows notebook PCs. It runs software written for Intel chips on a fraction of the power a Pentium consumes. The second, the TM3120, is a 400-MHz chip designed to run Internet appliances using a version of Linux that Torvalds developed for mobile devices.
Both chips present a face to software developers that is completely compatible with the instruction set in Intel’s processors. Underneath are VLIW chips, for “very long instruction word,” an architecture with a 128-bit-wide bus that can combine Intel chip instructions into longer strings and thus execute them faster. Between the outward-facing instruction set and the underlying hardware is Transmeta’s code-morphing software, which translates the Intel-style instructions into a form that Crusoe can handle, optimizes their execution and stores the optimized executions in memory. The next time the chip encounters the same operation, translation is no longer necessary. The code-morphing software (which resides in a read-only memory chip) is the first program to launch when the processor boots.
Because so much of Crusoe’s functionality has been moved from hardware to software, the chip is far simpler than a comparable Pentium processor and requires only one-fourth as many transistors. A side benefit of fewer transistors is that Crusoe uses far less power to run-hence Transmeta’s decision to target its first chips at the mobile market. Another advantage to the Crusoe approach is in shortening the time needed to develop a new chip. With much of the design residing in software, Ditzel says some customers have already asked for changes in the instruction set and that Transmeta engineers could implement them in 24 hours. While this probably doesn’t include time for any kind of bug testing, it’s nevertheless clear that Transmeta has found a way to drastically shorten the development cycle.
Nick Tredennick, co-architect of the original Motorola 68000 (the processor that powered the first Macintoshes), and now an independent microprocessor design consultant, is not alone in concluding Ditzel is on to something. “When I first heard about Crusoe, I thought it was just the latest fad, or a rehash of emulation, which has never worked,” Tredennick says. But after hearing Ditzel speak, Tredennick became a convert. Transmeta, he says, is doing something “fundamentally different from what has been done since the invention of the computer.”