Basic CPU structure (all CPUs are similar)


Most processors have some common characteristics and a standard sequence of steps they go through to execute a single instruction.

You will find working registers , which are essentially memory cells inside the CPU itself. Access to these locations is very fast, and, most of the time, instructions will use one or more of these registers to contain the data for the operation. Some CPUs offer the programmer a lot of working registers, some fewer. Some registers may be reserved for special use. Some may have special capabilities, such as automatically incrementing or decrementing the value they contain each time they are accessed.

In most CPUs you will see a processor status register , which will contain the state of the CPU, for example, whether it's in supervisor or kernel mode or in user mode. Various flags may exist that indicate the result of the most recent arithmetic operations (known as condition codes). It would be in the process status register that you might also find priority levels for handling interrupts and, possibly, error indication flags.

In all CPUs you will see a program counter , or a register that indicates where the CPU is getting instructions to be executed.

There may also be a stack pointer and some other dedicated or special-purpose registers that hold data relating to other, specific operations.



PANIC. UNIX System Crash Dump Analysis Handbook
PANIC! UNIX System Crash Dump Analysis Handbook (Bk/CD-ROM)
ISBN: 0131493868
EAN: 2147483647
Year: 1994
Pages: 289
Authors: Chris Drake

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