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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;.
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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 Random Access Memory Stores data and instructions Volatile Examples: RAM chips CMOS ROM Read Only Memory Stores basic system settings Non-volatile Example: BIOS RAM vs. ROM
Retrieving Data from Secondary Storage Cache: The papers in your hand are the next ones you will use! Notes in your locker, car, or at home, are too far away! RAM: The book on your desk is much closer!
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 RAM on the Motherboard
Different Types of DRAM • SIMM • Single Inline Memory Module • DIMM • Dual Inline Memory Module • RIMM • Rambus Inline Memory Module
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: • L1 • L2 • L3
Error Correction • Method used to: • Detect integrity of data stored in RAM • Ensure memory is complete • Prevent 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;
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;
Anything above 1 MB Reserved for device drivers and system functions Available to the user for any software