Very Long Instruction Word (VLIW) Processor

[VelMurugan]

Crusoe Processor

Transmeta released its Very Long Instruction Word (VLIW) processor Known as the Crusoe processor, it is a hardware-software hybrid that uses a code morphing technique to emulate the x86 architecture. Here software known as Code Morphing Software converts the normal x86 instructions into the native VLIW code. In this technique, software is loaded from the ROM upon boot up and used to control the scheduling of instructions. Compatibility with x86 applications is assured because this software is able to insulate programs from the hardware engine s native VLIW instruction set.

The code morphing technique keeps the core logic design of the Crusoe processor simple and provides a solution for the problems posed by traditional architectures. Avery low power consumption is one of the resultant benefits and this makes the Crusoe most suited for internet appliances and mobile applications.

As modern CPUs became more complex, they tend to have more hardware, and perform more functions than their early RISC predecessors. All that hardware requires lots of power though, and the more power a CPU draws the hotter it gets. When Transmeta designed the Crusoe system they went back to basics. They looked at the entire picture they did not just say how fast could we make this system they said, How efficient can we possibly make this, and still have it run x86 applications acceptably . So instead of having in the past one primary directive they had two. So certain things would have to be traded off to make this the best system possible. The three main things they wanted the system to have was:

1. Full x86 compatibility

2. The lowest possible power consumption

3. A level of x86 application performance that provides for a reasonably good user experience.