Computer Architecture Computer Architecture And OrganizationAnd Organization

UNIT-II

Multilevel View Point Of Multilevel View Point Of

A MachineA Machine

Multilevel View Point Of A MachineMultilevel View Point Of A Machine

Actual Multilevel ComputerActual Multilevel Computer

The Computer Level HierarchyThe Computer Level Hierarchy

Level 6: The User LevelLevel 6: The User Level

o Program execution and user interface level.Program execution and user interface level.

o The level with which we are most familiar.The level with which we are most familiar.

Level 5: High-Level Language LevelLevel 5: High-Level Language Level

o The level with which we interact when we The level with which we interact when we write programs in languages such as C, write programs in languages such as C, Pascal, Lisp, and Java.Pascal, Lisp, and Java.

The Computer Level HierarchyThe Computer Level Hierarchy

Level 4: Assembly Language LevelLevel 4: Assembly Language Level

o Acts upon assembly language produced Acts upon assembly language produced from Level 5, as well as instructions from Level 5, as well as instructions programmed directly at this level.programmed directly at this level.

Level 3: System Software LevelLevel 3: System Software Levelo Controls executing processes on the system.Controls executing processes on the system.o Protects system resources.Protects system resources.o Assembly language instructions often pass Assembly language instructions often pass

through Level 3 without modification.through Level 3 without modification.

The Computer Level HierarchyThe Computer Level Hierarchy

Level 2: Machine LevelLevel 2: Machine Level

o Also known as the Instruction Set Also known as the Instruction Set Architecture (ISA) Level.Architecture (ISA) Level.

o Consists of instructions that are particular to Consists of instructions that are particular to the architecture of the machine.the architecture of the machine.

o Programs written in machine language need Programs written in machine language need no compilers, interpreters, or assemblers.no compilers, interpreters, or assemblers.

The Computer Level HierarchyThe Computer Level Hierarchy

Level 1: Control LevelLevel 1: Control Levelo A A control unitcontrol unit decodes and executes decodes and executes

instructions and moves data through the instructions and moves data through the system.system.

o Control units can be Control units can be microprogrammedmicroprogrammed or or hardwiredhardwired. .

o A microprogram is a program written in a A microprogram is a program written in a low-level language that is implemented by low-level language that is implemented by the hardware.the hardware.

o Hardwired control units consist of hardware Hardwired control units consist of hardware that directly executes machine instructions.that directly executes machine instructions.

The Computer Level HierarchyThe Computer Level Hierarchy

Level 0: Digital Logic LevelLevel 0: Digital Logic Levelo This level is where we find digital circuits This level is where we find digital circuits

(the chips).(the chips).o Digital circuits consist of gates and wires.Digital circuits consist of gates and wires.o These components implement the These components implement the

mathematical logic of all other levels.mathematical logic of all other levels.

The Computer Level HierarchyThe Computer Level Hierarchy

Levels of RepresentationLevels of RepresentationHigh Level Language

Program

Assembly Language Program

Machine Language Program

Control Signal Specification

Compiler

Assembler

Machine Interpretation

temp = v[k];

v[k] = v[k+1];

v[k+1] = temp;

lwlw $15,$15, 0($2)0($2) lwlw $16,$16, 4($2)4($2) swsw $16,$16, 0($2)0($2) swsw $15,$15, 4($2)4($2)

0000 1001 1100 0110 1010 1111 0101 10001010 1111 0101 1000 0000 1001 1100 0110 1100 0110 1010 1111 0101 1000 0000 1001 0101 1000 0000 1001 1100 0110 1010 1111

ALUOP[0:3] <= InstReg[9:11] & MASK

Computers are designed as a series of levelsComputers are designed as a series of levels Each level represent a different abstraction (hence a Each level represent a different abstraction (hence a

different language)different language) The bottom level is the actual computer and its (real) The bottom level is the actual computer and its (real)

machine language (low-level language)machine language (low-level language) The top-level is for High-Level Languages (C,C+The top-level is for High-Level Languages (C,C+

+,Java, Prolog) easier for the final user+,Java, Prolog) easier for the final user The set of data types and operations of each level is The set of data types and operations of each level is

called an architecture.called an architecture. Choosing data types and operations for each level is Choosing data types and operations for each level is

a fundamental part of computer architecture designa fundamental part of computer architecture design

Multi-level organization: summaryMulti-level organization: summary