Not too long ago, we had a new contender come out in the CPU world. Its development was cloaked, no one had heard of it before for awhile. Slowly, though secrets started leaking (nice marketing) and people started talking about this little processor. Upon it’s release, absent was the talk of kick-ass speed and gaming power. No, instead, we heard about it’s voltage variation and power management features. The chip? The Crusoe, by Transmeta Corp.

The three most-talked of technologies for this processor were VLIW, Code Morphing, and the power management. Let’s look into them briefly:

VLIW

Very Long Instruction Word (VLIW) computing is not new. But, being done in a mass produced, publicly available processor is. Whereas other processors use the superscalar architecture to help in parallel processing via hardware, VLIW does this in the compiler. The compiler actually inspects the source code of the program, arranges the instructions into packets, each being designed to be run in parallel. This means that whatever instructions were in that packet can be executed at the same time. Crusoe can execute four instructions in parallel, so the VLIW compiler compiles the code into packets, each containing four instruction laid out for parallel processing. This data packet is called a molecule. This molecule is what gets processed by Crusoe. What does this mean? Well, being that this functionality is now in the compiler and not hard-wired into the chip, the chip itself can be smaller being that fewer transistors are needed. This in turn means less heat. This does, of course, mean that software is doing a lot more work, which inevitably means slower performance in the long run.

Code Morphing

Basically, this is referring to the VLIW compiler. It is different because it does “on-the-fly” translating of x86 code into the “molecules” discussed above. This x86 emulation is called the Code Morphing Layer. It is stored in a boot ROM and is loaded up whenever the processor powers up. This layer takes x86 code, breaks it up into packets, sends it to a cache, and off to the processor. The cache stores the frequently used code.

The neat thing about this design is that the Crusoe can run software of any platform. All they have to do is design a patch to the compiler to support the new instruction set. Of course, again, this whole process takes a little longer than a purely hardware solution, so performance does suffer from the traditional processor.

Power Management

One of the neatest things about Crusoe is its ability to adjust its MHz rating and voltage depending on the task at hand. For example, if you’re playing some kick-ass game, it would probably be running at full speed, yet if you were farting around and playing Solitaire, it would gear down the speed and voltage and thus hog less power. It also runs cooler.

What This Means

I remind you that the Crusoe was designed for mobile systems. It may run at 700 MHz, but it doesn’t necessarily get things done as fast as it could. The performance graphs show that it takes slightly longer than a processor of equal frequency, but it uses roughly a third of the power. This means that your laptop will run three times as long on the same battery during peak times. Please note that I say “during peak times”. When the processor has to translate things, it slows the process down. During idle times, the performance shows that the 400 MHz processor takes the exact same amount of time to complete the same task as the Pentium III 500 MHz. It also does so using only a fifth of the average power.

The chip will not likely be found in desktop PCs, rather it is designed for mobile systems. It was designed for internet applications, mobile systems, and other uses which require efficiency over sheer power. It uses a different processor package – the 474 BGA, which is about a quarter of the size of the standard Intel Chip. It runs at up to 166 MHz bus speeds, which means that it could be tweaked to around 233 MHz or more.

Transmeta Crusoe is indeed a cool little processor. It is worthy of mention because of the innovation, but it is not destined for the desktop PC. It is used in small notebooks, internet appliances and other types of applications that require portability and efficient power consumption.