x86 x64 Architecture 101

x86 and x64 have the same basic architecture with x64 (64bit) being a superset of x86 (32bit). We will call this these the Intel architecture from this point on in the tutorial. This tutorial will discuss what the registers, commands (opcodes), and usages of each are.

Processors are made up of various registers that store bytes of data. They vary in size depending on the register. Sometimes these registers even overlap each other. Various naming conventions are present in the naming of registers.

For information on the purpose and size of the registers see wikipedia:

• x86 List of registers
• Purpose
• x64 Differences

These architectures are single stack scalar architectures. Meaning that any given point in time there is a single program counter will only be determine what code to execute next.

The program counter is stored in a register just like any other piece of information in the processor. In the Intel architecture the register for this is called the Instruction Pointer (IP).