Inside the Machine

Chapter 8. Intel's Pentium 4 vs. Motorola's G4e: The Back End

In this chapter, I’ll explain in greater detail the back end of both the Pentium 4 and the G4e. I’ll talk about the execution resources that each processor uses for crunching code and data, and how those resources contribute to overall performance on specific types of applications.

Some Remarks About Operand Formats

Unlike the DLW and PowerPC ISAs described so far, the x86 ISA uses a two-operand format for both integer and floating-point instructions. If you want to add two numbers in registers A and B, the instruction would look as follows:

add A, B

This command adds the contents of A to the contents of B and places the result in A, overwriting whatever was previously in A in the process. ...