Understanding Memory and Memory Devices

Christina AngstadtKarlie Meyer

Kait Sharer

Overview1. History2. Intel 11033. Memory Modules4. Volatile vs. Non-Volatile5. ECC Memory6. Single Sided vs. Double Sided7. Parity vs. Non-Parity8. What is RAM?9. Types of RAM10. Single Channel vs. Dual Channel11. Memory Speeds12. Desktop vs. Laptop Memory13. How much RAM is enough?14. Memory Recommendations15. How to Install RAM

History

Punch Cards & Tape (-1970): helped to develop the ‘idea’ of main memory› How to store programs, data & results permanently

The Williams Tube (1948): storage device for Manchester Baby computer› Fired beam of electrons down a vacuum tube, then detected static

charges caused by the beam.› Store around 1Kb› Parallel with today’s DRAM chip

Also needed to be refreshed

Magnetic Core (1950 -1970): dominant form of technology› Magnetic ceramic rings called cores› Stored information using polarity of magnetic field› Access speeds between 6msec – 1.2msec

Card from a Fortran program

Z(1) = Y + W(1)

Intel 1103

First Dynamic RAM chip Developed by Intel (1970) 1 Kb of DRAM

› Entire refresh done in 32 read cycles› Required every 2 ms

Replaced magnetic core technology for main memory› Faster (ns) compared to core (ms)

Best selling semiconductor memory chip by 1972 High data capacity & Low cost

› (1 cent / bit) Allowed for first mass-produced home computers (PC’s)

Memory Modules

SIMM (Single Inline Memory Module)

8MB RAM 30 or 72

Connector contacts

DIMM (Dual Inline Memory Module)

64MB RAM 168 Connector

contacts (pins) Two pairs of

SIMMs on a single board

Circuit Board that holds memory chips• Connects to motherboard

Volatile vs. Non-Volatile

Data is lost when powered down Form of primary storage

› Directly accessible to CPU RAM (Random-Access Memory) Faster to read from/write to Needs to be periodically refreshed DRAM

Retains stored data even when not powered Used for long-term (secondary) storage ROM (Read-Only Memory)

› Data cannot be modified› Fast & expensive

Flash Memory Magnetic storage devices

› Hard disk drive› Cheaper but slower

ECC Memory

Error-Correcting Code Memory› Introduced by HP in 1993

Detects and corrects some memory errors› Different from parity (only detects)› RAM was not as stable as it is today› Irregularities could cause data in memory to corrupt

System crash Hard disk data damage

› An additional bit is appended to each byte of RAM Verifies the validity of each byte

Slow system to about 2% More expensive Recommended for servers

› Unnecessary otherwise, due to low error rate in today’s memory

ECC Memory

58

40

1

0

Single Sided vs. Double Sided

8 memory chips on one side (or 4 on each side) All of the chip’s memory can be seen at the same

time› Both sides

Denser memory modules Larger capacity chips

› 32M Lower latency times (delay)

16 memory chips (8 on each side) Only one side can be seen by the computer at a time

Chip capacity of 16M

Slightly slower

Parity vs. Non-Parity What is Parity Memory?

› Parity memory includes one extra bit of storage for every 8 bits of data

Advantages› Data Integrity› Easier Troubleshooting› Advanced Warning of

Hardware Failure› Parity memory usually works in

a Non-parity system Disadvantages

› Greater Expense› Harder to Find› Occasional False Positives› Poor Error Handling› Performance Penalty for ECC

What is Non-Parity Memory?› “Regular” memory,

One bit of storage for each bit of data

Advantages› Cheaper› Easier to Find b/c more

is produced› Little faster than ECC

Disadvantages› Non-parity memory will

not work in a parity system

What is RAM?

Volatile Temporary Storage “Random Access

Memory” : Can access any memory cell directly

Many Types:› DRAM› SRAM› SDRAM› DDR/DDR2/DDR3› RAMBUS

Types of RAM

DRAM= “Dynamic RAM”› Most Common Form of Memory› 1 Transistor and 1 Capacitor Paired› Create Memory Cell = Bit› Bit holds 0 or 1› Transistor is a switch› Capacitor = Bucket

Store “1” fills with electrons Store “0” bucket emptied Bucket has a leak Recharge Capacitors holding a 1

› Refresh Operation: CPU or Memory Controller Reads & Writes Back 1000s of times per second DRAM has to be dynamically refreshed Takes time and slows down memory

Types of RAM cont.

DRAM cont.› Forms the larger system RAM space› Advantages

Structural simplicity One transistor One Capacitor

Reaches Very high Density Cheaper than SRAM

› Disadvantages Slower than SRAM Has to constantly be reminded what is being

stored

Types of RAM cont.

SRAM = “Static RAM”› Flip-flop holds each bit› 4 or 6 transistors & some wiring› Never has to be refreshed› Creates the CPU’s speed-sensitive cache› 3 different states

Standby: Idle Reading: Data Requested Writing: Updating Contents

Types of RAM cont.

SRAM cont.› Used where bandwidth or lower power are

principle considerations› Advantages

Significantly faster than DRAM Less power hungry (Especially Idle) Easier to control

› Disadvantages Takes up more space Less memory per chip More expensive Complex Internal Structure (less dense)

Types of RAM cont.

SDRAM = “Synchronous Dynamic RAM”› Started in 1993› Typical DRAM is asynchronous : responds

as quickly as possible to changes in control inputs

› SDRAM is synchronous Waits for a clock signal before responding to

control inputs Synchronized with the computer’s bus

system

Types of RAM cont.

SDRAM cont.› Chip has a more complex pattern of

operation than asynchronous DRAM› Widely used in computers› Ability to interleave operations to multiple

banks of memory, increasing effective bandwidth

› Single Data Rate: Only one word of data transmitted per clock cycle

› Supply Voltage 3.3V

DDR/DDR2/DDR3

Types of RAM cont.

DDR SDRAM = “Double Data Rate SDRAM”› Reads/Writes 2 words of data per clock cycle› Supply Voltage reduced to 2.5V› Doubles the minimum read or write unit

DDR2 SDRAM “Double Data Rate 2 SDRAM”› Doubles the minimum read or write again to 4

consecutive words› Simplified to allow higher performance operation› Allows bus rate of the SDRAM to be doubled w/o

increasing clock rate of internal RAM operations

Types of RAM cont.

DDR3 SDRAM: “Double Data Rate 3 SDRAM”› 1.5V› Doubles the minimum read or write unit to 8

consecutive words› Doubling of bandwidth and external bus rate w/o

having to change the clock rate of internal operations, just the width

› With every doubling comes increased latency DDR4 SDRAM: “Double Data Rate 4 SDRAM”

› Release in 2012› Proposed to run at 1.2V or less› 2 billion data transfers per second

Types of RAM cont.

Rambus DRAM› Types of synchronous dynamic RAM designed

by the Rambus Corporation› Data transferred on both rising and falling

edges of the clock signal (DDR)› Shows a slight increase in latency, heat

output, manufacturing complexity, and cost› Uses a Rambus in-line Memory Module (RIMM)› Operates at higher speeds than normal DRAM› Fitted with a heat spreader to help dissipate

the excess heat

Single Channel vs. Dual Channel Memory Single Channel Memory

› Memory bus of 64 bits

Dual Channel Memory› doubles data

throughput from the memory to the memory controller

› Utilizes two 64-bit data channels, resulting in a 128-bit data path

Dual Channel Memory

• Requires a dual-channel-capable motherboard and two or more DDR, DDR2 SDRAM, or DDR3 SDRAM memory modules

• Separate channels allow each memory module access to the memory controller, increasing throughput bandwidth

• Requires two memory modules plugged into the appointed DIMM slots in order to enable 2 Channel DDR.

• Dual-channel technology was created to address the issue of bottlenecks– Under the single-channel architecture, any CPU with a bus speed

greater than the memory speed would be susceptible to this bottleneck effect

– Dual-channel configuration solves this problem by doubling the amount of available memory bandwidth. Instead of a single memory channel, a second parallel channel is added. With two channels working simultaneously, the bottleneck is reduced.

Memory Speeds PC100 PC133 PC2700 PC3200 DDR2-667 DDR3-1600

PC100

Synchronous DRAM › operating at a clock frequency of 100 MHz › 64-bit bus› voltage of 3.3 V

PC100 is a standard for internal removable computer random access memory

PC133

Synchronous DRAM› operating at a clock frequency of 133 MHz› 64-bit-wide bus› voltage of 3.3 V

PC133 was the fastest and final SDRAM standard ever approved by the JEDEC, and delivers a bandwidth of 1064 MB per second

Backward compatible with PC100

PC2700

Double Data Rate(DDR)-Synchronous DRAM› transfers data on both the rising and falling

edges of the clock signal (double pumping) to lower the clock frequency

› operating at a clock frequency of 166 MHz› Data transfer rate: 333MHz› Peak transfer rate is 2700 MB/s

PC3200

Double Data Rate(DDR)-Synchronous DRAM; same concept as PC2700 except:› operating at a clock frequency of 200 MHz› Data transfer rate: 400MHz› Peak transfer rate is 3200 MB/s

DDR2-667

• DDR2 SDRAM is a double data rate synchronous dynamic random access memory interface

• Supersedes the original DDR SDRAM– Not compatible with DDRM SDRAM

• Double pumping the data bus as in DDR– DDR2 allows higher bus speed

• Key difference between DDR and DDR2:– Requires lower power by running the internal clock at

one quarter the speed of the data bus

– Memory clock: 166 MHz– Peak transfer rate: 5333 MB/s

DDR3-1600

• DDR3 SDRAM or double data rate three synchronous dynamic random access memory – random access memory interface technology

used for high bandwidth storage• Ability to transfer at twice the data rate of

DDR2 – Memory clock: 200 MHz– Data Rate: 1600 MT/s– Peak Transfer Rate: 12800 MB/s

• Not compatible with DDR2

Desktop vs. Laptop Memory

Desktop› DIMMS (Dual In-

Line Memory Module) SDRAM DDR SDRAM DDR2 SDRAM DDR3 SDRAM

Laptop› SO DIMM (Small

Outline DIMM) Smaller version of

DIMM modules used in desktops

Laptop Memory

Form factors of laptop memory differ from that of desktop memory including:› Physical size› Pin configuration

Full size DIMM:• 100, 168, 184, or 240 pins• 4.5 to 5 inches in length

SO DIMM› 72, 100, 144, or 200 pins› 2.5 to 3 inches in length

How Much RAM is Enough?

Depends on the O.S.› Windows 98: Operating System and the programs

that run on it are less complex 512 MB – 2GB

› Windows XP Professional 512MB – 4GB

› Windows 7 (32-bit) 1GB – 4GB

› Mac OS X 512MB – 4GB

› Linux 64MB

How Much RAM is Enough?

Depends on computer’s functions› Casual User: Internet browsing, e-mail, music

512MB – 1GB› Frequent User: Internet browsing, e-mail, word processing,

simple graphics programs and games, music & videos, multitasking 1GB – 2GB

› Power User/Student: Internet browsing, e-mail, word processing, photo & video editing, graphics programs & gaming, intensive multitasking 2GB – 4GB

› Professional User: High performance gaming, multimedia editing, high-def video, graphics design & 3D modeling, intensive multitasking 4GB – 8GB

More memory allows you to run more programs at once, and make them easier to use.

Memory RecommendationsSoftware

MinimumRequirements

CrucialRecommendations

Adobe® Acrobat® 6.0 Standard 64MB 128MB

Microsoft FrontPage® 2003 128MB 512MB

Adobe Illustrator® CS 128MB 512MB

Adobe Photoshop® CS 128MB 1GB-1.5GB

Adobe Premiere® Pro 256MB 1GB +

Adobe After Effects® 6.0 128MB 1GB-1.5GB

SoftwareMinimum Requirements

Crucial Recommendations

Half-Life® 2: Lost Coast™ 256MB 1.5-2GB

Battlefield® 2™ 512MB 2GB

Call of Duty 2™ 512MB 1.5GB

Star Wars® Battlefront™ 2 512MB 1.5GB

Medieval II: Total War™ 512MB 1GB-2GB

Need for Speed™ Carbon 256MB 1GB-2GB

Tom Clancy's Splinter Cell: Double Agent™ 512MB 1GB-2GB

Call of Duty World at War 1GB 2GB-4GB

Design Software:

Gaming Software:

How to Install RAM

What you need to know:› How much RAM you have

C:\> MEM› How much RAM you wish to add

Usually sold in multiples of 16MB› Form factor

Card type (DIMM / RIMM)› RAM type

Some computers require specific types of RAM to operate Should match existing RAM in type, speed and parity for optimal

performance Most common type is SDRAM

› Warranty› Where it goes

Installing RAM in a DesktopInstalling RAM in a Laptop