CP1610:Introduction to Computer Components

Primary Memory

What is Memory?

Memory is used to:Store data;Store commands (instructions);Store system settings;

Computer Memory

Three categories of memory devices:Primary Memory;Secondary Memory;Archival Storage Devices;

What is Primary Memory?

Also called system memory. Essential for computer to operate. Stores data and commands to be used by the

CPU. Stores basic system settings. Two main types:

RAM ROM

RAM vs. ROM

RAM Random Access

Memory Stores data and

instructions Volatile

Examples: RAM chips CMOS

ROM Read Only Memory Stores basic system

settings Non-volatile

Example: BIOS

The Primary Memory Hierarchy

Notes in your locker, car, or at home, are too far away!

Retrieving Data from Secondary Storage

RAM: The book on your desk is much closer!

Cache: The papers in your hand are the next ones you will use!

RAM on the Motherboard

Static RAM (SRAM) Very fast; Expensive; Does not need to be

refreshed; Used as Cache; On Chip, Coast Card,

or inside CPU;

Dynamic RAM (DRAM) Slow; Cheaper; Needs constant

refreshing; Used as RAM; SIMMs, DIMMs and

RIMMs

Different Types of DRAM

SIMMSingle Inline Memory Module

DIMMDual Inline Memory Module

RIMMRambus Inline Memory Module

Installing a SIMM Chip

Installing a DIMM Chip

Installing a RIMM Chip

Older Types of RAM

Conventional RAM Fast Page Memory (FPM) Extended Data Out (EDO) RAM Burst EDO (BEDO) RAM

Newer Types of RAM

Sychronous DRAM (SDRAM) Synced with system clock

Double Data Rate (DDR) SDRAM Most popular today 184-pin DIMMs 200-pin SODIMMs

Rambus DRAM (RDRAM) Not as common Faster system bus RIMMs

Cache Memory Very fast SRAM Used to store the very next command or

data needed by the CPU Three Types:

L1L2L3

Error Correction Method used to:

Detect integrity of data stored in RAMEnsure memory is completePrevent data corruption or loss

Non-Error Correcting Memory:Used in older systems to speed up memory;

Types of Error Correction

Parity:Older;Cannot correct data corruption;

Error Correcting Code (ECC):Newer;Most widely used;Can correct data corruption;

How Parity Works

System Memory

Conventional Memory: First 1 MB of memory; Used to run programs and store system drivers;

High Memory (Hi-Mem): About 64 KB of memory just above the 1 MB point;

Extended and Expanded Memory: Anything above 1 MB; Systems must run in ‘Protected Mode’ to use;

Available to the user for any software

Reserved for device drivers and system functions

Anything above 1 MB