Types of RAM (Random Access Memory) Information Technology

What is RAM Memory? RAM typically resides on Memory Modules A RAM Memory chip is an integrated circuit made of millions of Transistors and Capacitors Most RAM is Volatile (loses electrical charge when power goes off) There are various types of RAM (DRAM, SRAM, VRAM) Virtual Memory (An extension of RAM on the hard drive)

Typically RAM chips reside on memory modules. Four main types exist. SIMMs DIMMs SODIMMs RIMMs

SIMMs Single Inline Memory Module Pins on opposite sides form a single set of contacts

DIMMs Dual Inline Memory Module 168 Pins on opposite sides of the circuit board form separate connections

SODIMMs Small Outline Dual In-line Memory Module A much smaller form of memory Used in Notebook computers and Apple iMac desktops

RIMMs RAMbus Inline Memory Module RDRAM Comparable in size and pin configuration to DIMM but uses a special memory bus to greatly increase speed.

How does RAM store information? Integrated Circuits How does RAM store information? -Address lines -Transistors -Data lines -Capacitors

Most RAM must be recharged constantly Volatile Memory losses contents when power is removed

Some RAM types use Parity Checking Even Parity Checking, parity bit is set to “0“ when byte is even. 001001000 9th bit is parity bit 0 Odd Parity Checking, parity bit is set to "1" when byte is even. 111001111 9th bit is parity bit of 1

Error Control High-end servers often have a form of error-checking known as error correction code (ECC). Bits can be corrected after failure, however, if more than one bit is corrupted the entire byte of data is lost.

What are some different types of Random Access Memory ? RAM Types What are some different types of Random Access Memory ?

Types of Dynamic RAM (DRAM) SDRAM – Synchronous DRAM Synchronized to the system clock DDR SDRAM (Double Data Rate SDRAM) Transfer data twice for each clock cycle Rambus DRAM (RDRAM) Faster than SDRAM chips because they use pipelining techniques

Types of Dynamic RAM Stores 1’s and 0’s on capacitors Must be recharged every millisecond, or every one thousandth of a second Many different types exist (previous slide)

Fast Page Mode DRAM First form of DRAM Maximum transfer rate to L2 cache is approximately 176 megabytes per second.

EDO DRAM EDO = Extended Data Out Resides on SIMMs Sends and receives data simultaneously Maximum transfer rate to L2 cache is approximately 264 megabytes per second.

Synchronous DRAM Resides on DIMMs Faster than previous DRAM because it is synchronized with the system clock Maximum transfer rate to L2 cache is approximately 528 megabytes per second. Most common choice of Pentiums until recently

Double Data-rate SDRAM Resides on DIMMs Also known as SDRAM II Faster than SDRAM because it transfers data twice for each clock cycle Commonly used in PCs

RAMbus DRAM Resides on RIMMs Uses a pipelining technique to increase speed RDRAM memory chips work in parallel to achieve a data rate of 800+ MHz.

DRDRAM Direct Rambus DRAM by Rambus, Inc. Often called PC800 RAM (doubling the Pentium 4 chip’s 400 MHz bus speed) Like DDR SDRAM, it transfers data on the rising & falling edges of the clock cycle Uses 2 data channels to improve transfer rates

Static RAM Often used for Cache Memory Very fast and reliable because these chips do not have to be recharged as often as DRAM chips hence the term “static” SRAM chips: more expensive than DRAM

Static RAM Cache Memory (Static RAM) helps speed up the microprocessor. Cache Memory stores frequently used data and instructions.

Static RAM Personal Computers have 2 and perhaps 3 types of cache memory: L1 (Level 1) Cache (8KB to 128KB) L2 (Level 2) Cache (64KB to 4MB) L2 Advanced Transfer Cache on current microprocessors (built on the chip)

Static RAM L3 (Level 3) Cache is cache separate from the microprocessor chip and is on the motherboard. L3 Cache exists only on computers that use the L2 Advanced Transfer Cache.

Static RAM A computer with L2 cache usually performs at speeds 10 to 40 percent faster than those without cache. Servers and workstations can have at least 2MB of L2 or L3 cache.

SGRAM Synchronous Graphics RAM SGRAM is a variant of SDRAM SGRAM makes use of block-writes to increase video processing speeds. SGRAM is single-ported so the CPU cannot write to it at the same time the image is being refreshed. SGRAM is used in high-end graphics cards

How much RAM do you need? What OS are you running ? What applications do you run? Computer animation and graphics? Several functions? Win 2000/XP – 128MB Win 95/98 – 64 MB Linux – 64 MB Mac OS – 128 MB

Virtual Memory Virtual memory takes the place of RAM memory You should have a 2:1 ratio of RAM to Virtual Memory

Modifying Virtual Memory in Windows

Modifying Virtual Memory in Windows 2000

End of RAM presentation