"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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