Copyright © 2007 Elsevier Digital Design and Computer Architecture David Money Harris and Sarah L. Harris

Copyright © 2007 Elsevier

Digital Design and Computer Architecture David Money Harris and Sarah L. Harris


• Jumping up a few levels of abstraction.

• Architecture: the programmer’s view of the computer– Defined by instructions (operations)

and operand locations• Microarchitecture: how to

implement an architecture in hardware

Physics

Devices

AnalogCircuits

DigitalCircuits

Logic

Micro-architecture

Architecture

OperatingSystems

ApplicationSoftware

electrons

transistorsdiodes

amplifiersfilters

AND gatesNOT gates

addersmemories

datapathscontrollers

instructionsregisters

device drivers

programs


• Microarchitecture: how to implement an architecture in hardware

• Processor:– Datapath: functional blocks– Control: control signals

Physics

Devices

AnalogCircuits

DigitalCircuits

Logic

Micro-architecture

Architecture

OperatingSystems

ApplicationSoftware

electrons

transistorsdiodes

amplifiersfilters

AND gatesNOT gates

addersmemories

datapathscontrollers

instructionsregisters

device drivers

programs


Assembly Language• To command a computer, you must understand its

language.– Instructions: words in a computer’s language– Instruction set: the vocabulary of a computer’s language

• Instructions indicate the operation to perform and the operands to use.– Assembly language: human-readable format of instructions– Machine language: computer-readable format (1’s and 0’s)

• Once you’ve learned one architecture, it’s easy to learn others.


Operands

• A computer needs a physical location from which to retrieve binary operands

• A computer retrieves operands from:– Registers– Memory– Constants (also called immediates)


Operands: Registers

• Memory is slow.• Most architectures have a small set of (fast) registers.• A 32-bit architecture operates on 32-bit data.


The Stack

• Memory used to temporarily save variables

• Like a stack of dishes, last-in-first-out (LIFO) queue

• Expands: uses more memory when more space is needed

• Contracts: uses less memory when the space is no longer needed


The Stack

Data

7FFFFFFC 12345678

7FFFFFF8

7FFFFFF4

7FFFFFF0

Address

$sp 7FFFFFFC

7FFFFFF8

7FFFFFF4

7FFFFFF0

Address Data

12345678

$sp

AABBCCDD

11223344

• Grows down (from higher to lower memory addresses)• Stack pointer: $sp, points to top of the stack


Addressing Modes

How do we address the operands?• Register Only• Immediate• Base Addressing• PC-Relative• Pseudo Direct


Microarchitecture

• Multiple implementations for a single architecture:– Single-cycle

• Each instruction executes in a single cycle– Multicycle

• Each instruction is broken up into a series of shorter steps– Pipelined

• Each instruction is broken up into a series of steps• Multiple instructions execute at once.


Processor Performance

• Program execution time

Execution Time = (# instructions)(cycles/instruction)(seconds/cycle)

• Definitions:– Cycles/instruction = CPI– Seconds/cycle = clock period– 1/CPI = Instructions/cycle = IPC

• Challenge is to satisfy constraints of:– Cost– Power– Performance


Architectural State

• Determines everything about a processor:– PC– Registers– Memory


Multicycle Processor

• Single-cycle microarchitecture:+ simple- cycle time limited by longest instruction (load)- two adders/ALUs and two memories

• Multicycle microarchitecture:+ higher clock speed+ simpler instructions run faster+ reuse expensive hardware on multiple cycles- sequencing overhead paid many times

• Same design steps: datapath & control


Control Unit

Documents

Copyright © 2007 Elsevier Digital Design and Computer Architecture David Money Harris and Sarah L. Harris