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Motley Fool: Inside Intel Again: Merced vs. Crusoe

Feb 26, 2000, 05:40 (5 Talkback[s])
(Other stories by Rob Landley)

"The Crusoe translates IA32 instructions to VLIW in software and reorganizes the resulting code to keep all the processor cores busy. This is done by a VLIW program Transmeta calls the 'Code Morphing' layer (very similar to Sun's Java JIT compiler). Instead of translating each instruction every time it sees it, the Crusoe keeps large chunks of translated instructions around in memory (actually in the CPU cache, which the Crusoe VLIW instruction set can address manually). This way, the Crusoe can spend more time executing translated instructions rather than retranslating them, and if it finds itself executing the same piece of code over and over, it can go back and put extra effort into optimizing it and reorganizing the instructions and such."

"The other really cool thing about Transmeta's chips is their lack of heat. They were designed from the ground up for use in portable devices, and thus use much less power than anything else. (In part, this is because they need a lot less circuitry than a Pentium does because they moved so many tasks from hardware to software.) A Crusoe chip only uses one watt of power to run at full speed, and can scale back both its clock speed and its voltage to slow down when it doesn't need that much. What determines how much speed is needed, and controls the voltage and the clock? The code morphing layer, of course. So Crusoe goes in your wristwatch without draining the battery, rather than in a desktop with a big power supply and heat sinks everywhere."

"But one big reason I think the Code Morphing approach is superior to what Intel is doing is that the underlying hardware can change. Intel is going through a big shock to introduce the IA64 instruction set, which is important because 32 bits isn't enough anymore and programs have to be rewritten. But if it decides to add more processor cores to each VLIW bundle in the future, programs will have to be recompiled AGAIN. Isolating those kind of details behind a layer of housekeeping software is just a whole lot tidier."

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