Processors

Processors 

The CPU
Central Processing Unit
Brain of the computer
Control Unit
o Controls resources in computer
o Instruction set Arithmetic & Logic Unit
o Simple math operations
o Registers
Floating-Point Unit
o Simple math operations
o Registers
Building Blocks of Microprocessor

 Processor Images

               Processor Images

Processor Images

Bus Interface Unit

Receives instructions and data from main memory
Instructions sent to instruction cache
Data sent to data cache
Also receives processed data and sends to main memory

Instruction Decoder

Receives programming instructions
Decodes instructions for understanding at processing units
ALU
FPU
Passes on the decoded instruction to ALU or FPU

Arithmetic & Logic Unit (ALU)

Also known as the “Integer Unit”
Performs whole-number math
Calculations (subtract, multiply, divide etc.)
Comparisons (is greater than, is smaller than, etc.)
Logical operations (NOT, OR, AND, etc.)
Latest microprocessors have two identical ALU’s
Perform calculations simultaneously
Double the capability

Floating-Point Unit (FPU)

Also known as the “Numeric Unit”
Performs calculations involving numbers with scientific notation
Floating-point numbers
Represents extremely small and extremely large numbers
In compact form
Floating-point calculations are required for working in
Graphics
Engineering
Science and research
ALU can do these calculations as well
But very slowly

Registers

ALU and FPU have private memory called registers
Small amount but super-fast
Placed right next to them
For exclusive use
Storage of intermediate and final results from calculations in registers
Processed data goes back to the data cache from registers
Data cache sends data to main memory

Control Unit

The brain of microprocessor
Manages the whole microprocessor
Tasks include
Fetching instructions & data
Storing data
Managing input/output devices
Controlling resources in computer

Instructions Set

Set of machine instructions
Recognizable at microprocessor
Executable at microprocessor
The only language microprocessor knows
An instruction set includes low-level, a single step-at-a-time instructions
Add, subtract, multiply, and divide
Each microprocessor family has its unique instruction set
Bigger instruction-sets mean more complex chips
Higher costs
Reduced efficiency
Shorter programs

Machine Cycles

Steps by CPU to process data
Instruction cycle
CPU gets the instruction
Execution cycle
CPU performs the instruction

Fetching
CU must fetch a command or data from computer’s memory.
Decoding
CU break down the commands into instructions
Executing
CPU carries out the instructions in order
Storing
Store results in memory (not always required)
Billions of cycles per second
Pipelining processes more data
Begins executing a new instruction before the current cycle is completed
20 instructions simultaneously
E.g. Intel Pentium IV
Multitasking allows multiple instructions
CPU makes threads of programs (thread = instruction)
Execute one thread from a program at a time
User thinks as if each program is being run simultaneously

Hyperthreading

allows multiple threads to be executed at one time
Allows multiple threads to be executed at one time
Processor can execute two (rather than one) concurrent streams (or threads) of instructions
o CPU and simulated CPU