The Basic Organization of Computers

Today’s Menu Daal chawal without salad, chatni and

achaar

Motherboard

based on stored program design

processor system CPU memory

input/output system input/output

devices secondary storage

Electronic Digital Computers

manages the instruction-execution cycle FETCH – DECODE – EXECUTE coordinates the activities of other devices

Central Processing Unit

The CPU and Main Memory

Inside the CPU

Inside the CPU

memoryaddressregister

memoryaddressregister

memorydataregister

Inside the CPU

memoryaddressregister

memorydataregister

programcounter

Inside the CPU

memoryaddressregister

instructionregister

memorydataregister

programcounter

Inside the CPU

memoryaddressregister

instructionregister

memorydataregister

programcounter

arithmeticlogic unit

Inside the CPU

memoryaddressregister

instructionregister

memorydataregister

programcounter

accumulator(workregister)

arithmeticlogic unit

Inside the CPU

memoryaddressregister

instructionregister

memorydataregister

programcounter

accumulator(workregister)

arithmeticlogic unitsystem

clock

Inside the CPU

1. address of thenext instruction istransferred fromPC to MAR

2. the instruction islocated in memory

FETCH the instruction

3. instruction iscopied frommemory to MDR

FETCH the instruction

instruction istransferred to and decoded inthe IR

DECODE the instruction

control unitsends signalsto appropriatedevices to causeexecution of theinstruction

EXECUTE the instruction

Data Movement Operations moving data from memory to the CPU moving data from memory to memory input and output

Arithmetic and Logical Operations integer arithmetic comparing two quantities shifting, rotating bits in a quantity testing, comparing, and converting bits

Types of Processor Operations

Program Control starting a program halting a program skipping to other instructions testing data to decide whether to skip over

some instructions

Types of Processor Operations

PROCESSOR REGISTERS

A processor has many registers to hold instructions, addresses, data, etc

The processor has a register, the Program Counter (PC) that holds the memory address of the next instruction to get

Since the memory in the Basic Computer only has 4096 locations, the PC only needs 12 bits

In a direct or indirect addressing, the processor needs to keep track of what locations in memory it is addressing: The Address Register (AR) is used for this

The AR is a 12 bit register in the Basic Computer

PROCESSOR REGISTERS When an operand is found, using either direct

or indirect addressing, it is placed in the Data Register (DR). The processor then uses this value as data for its operation

The Basic Computer has a single general purpose register – the Accumulator (AC)

PROCESSOR REGISTERS

The significance of a general purpose register is that it can be referred to in instructions

e.g. load AC with the contents of a specific memory location; store the contents of AC into a specified memory location

Often a processor will need a scratch register to store intermediate results or other temporary data; in the Basic Computer this is the Temporary Register (TR)

PROCESSOR REGISTERS

The Basic Computer uses a very simple model of input/output (I/O) operations

Input devices are considered to send 8 bits of character data to the processor

The processor can send 8 bits of character data to output devices

The Input Register (INPR) holds an 8 bit character gotten from an input device

The Output Register (OUTR) holds an 8 bit character to be send to an output device

PROCESSOR REGISTERS

Registers in the Basic Computer

11 0PC

15 0IR

15 0TR

7 0OUTR

15 0DR

15 0AC

11 0AR

INPR0 7

Memory

4096 x 16

CPU

Machine Cycle

A Machine cycle is a series of operations performed to execute a program instruction.

It consists of two parts:

1) Instruction cycle

2) Execution cycle

Instruction Cycle1) Fetching2) Decoding

During the instruction cycle, the CPU fetches (Gets) a command or data from main memory and decodes it (Determines what it means)

Execution Cycle1) Executing2) Storing

During the execution cycle, the CPU executes the instruction (Performs the Operation on the data), and may store the instruction's result in memory/Register

Processing Speeds There are three ways in which processing speeds

are measured:1) Time to complete one machine cycle in fractions

of a second.2) Time to complete instructions in millions of

instructions per second.3) Time in floating point operations per second.

Factors Affecting Processing Speed Registers – temp memory area – 32 bit Memory and computing power - RAM System clock – Hz – cycles - GHz The bus – the highway The data bus – CPU & devices The address bus – CPU & RAM Cache memory – L1(CPU resident), L2 (External)

31

Intel Processors

Current Intel processors

32

Intel Processors (cont’d.)

Current Intel processors (continued)

33

AMD Processors

Current AMD processors

34

Beep Codes and Their Meanings