12 it2003

RANDOM ACCESS MEMORY 1

M.KUMARASAMY COLLEGE OF ENGINEERING

(AUTONOMOUS)

01/10/2013

Guided by,

R.MOHAN,M.Tech

AP/IT DEPT,

Presented by,M.ANAND(12BIT2003),

R.JEGANATHAN(12BIT2024),A.KARTHIKA(12BIT2027),

R.KEERTHANA(12BIT2032),P.KIRUTHIKA(12BIT2033)

RANDOM ACCESS MEMORY 201/10/2013


What is RAM…?

Characteristics of RAM,

Types of RAM,

LATEST RAMs,

Other applications,

RAM Vs ROM,

Conclusion.

AGENDA…


INTRODUCTIONRandom-access memory (RAM) is a form of computer data storage. Access stored data in any random order. form of integrated circuits.

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CHARACTERISTICS OF RAM

Volatile;

memory controller;

It allows reading and writing;

Store many words, one per address;

Read and write at a particular address;

space in megabytes(but now in GB);

speed in nanoseconds.01/10/2013

6

WHY WE GO FOR RAM….?

To read data quickly to run applications. As Memory cells that can be accessed to transfer data.

01/10/2013 RANDOM ACCESS MEMORY

Hard disk RAM processor


EVOLUTION:The first RAM modules in 1951 until(1960s-1970s)1st generation- MRAM ( 128 KB)in 2003. In June 2004, Infineon Technologies - 16 MB RAM.Since 2006, "solid-state drives“

-256 GB become available. difference in performance.

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BLOCK DIAGRAM OF RAM

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CS- enables or disables the RAM.ADRS- specifies the address to read from or write to.WR-selects reading from or writing to the memory.

To read from memory, we set WR=0.To write to memory, we set WR = 1.

2k x n memory

ADRS OUTDATACSWR

kn

n


TYPES OF RAM

RAM

DYNAMIC

S-DRAM A-DRAM

STATIC

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STATIC RAMA type of semiconductor memory.

Modeled using one latch for each bit

of storage.

A latch consists of more than 5

transistor.

Uses bistable latching circuitry to store

each bit.01/10/2013


Contd.,most commonly used in video

cards.

more expensive.

less dense than DRAM.

An SRAM cell has three different

states.

standby (the circuit is idle),

reading (the data has been

requested)

writing (updating the contents).

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DYNAMIC MEMORYA single bit of data can be stored with just

one capacitor and one transistor.

physically smaller than SRAMs.

requires constant refreshing.

Memory lasts for Few milliseconds

used for a computer’s main memory.

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Contd.,

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disadvantage of DRAM is its

speed.

Uses a circuit that acts like a

capacitor.

Types:

Synchronous dram,

Asynchronous dram.


SYNCHRONOUS DRAMMemory chips are organized into

“modules”-connected to the CPU

Speeds are rated in megahertz

revises the asynchronous memory

interface.

All other signals are received on the

rising edge

of the clock.

The /RAS and /CAS inputs along with

/WE.

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Contd., programmed into the SDRAM chip itself, called CAS latency.The "Load mode register" command is used to transfer this value to the SDRAM chip. support for multiple internal banks inside the DRAM chip. keep the data bus busy.

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ASYNCHRONOUS DRAM

it has power connections, address inputs,

& a bidirectional data lines.

Four active-low control signals:

/RAS, the Row Address Strobe.

/CAS, the Column Address Strobe.

/WE, Write Enable.

/OE, Output Enable.

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Contd.,

the signals are generated by a clocked

memory controller,

RAS Only Refresh (ROR)

CAS before RAS refresh (CBR)

Hidden refresh

Classic asynchronous DRAM is refreshed

by opening each row in turn.01/10/2013


MODERN RAMs:Double Data Rate RAM

Similar to regular SDRAM. memory speeds be 200-266MHz. lower power consumption. good for notebooks and other mobile devices.

RDRAMin Play station 2 & pentium 4

computers.transfer rate of 1.6GB per second.

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OTHER USES OF RAMVirtual memory:

A part of the hard drive is set aside for a paging file . physical RAM +paging file = virtual memory. "swap" portions of RAM to the paging file .

RAM disk:Shadow RAM:

Shadowing, in computers & embedded systems. “use shadow BIOS” ROM will use DRAM locations.

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RECENT DEVELOPMENTS: Non-volatile RAM

Carbon nanotubes are used.

Thermal Assisted Switching (TAS) by crocus technology. Spin Torque Transfer (STT) by CROCUS, HYNIX, IBM technologies."Eco RAM", for low power consumption.

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RAM vs ROM RAM ROM

DEFINITION a form of data storage that can be accessed randomly at any time, in any order and from any physical location.

a form of data storage that can not be easily altered or reprogrammed.

STANDS FOR Random Access Memory Read-only memory

USE read data quickly to run applications. It allows reading and writing.

stores the program required to initially boot the computer. It only allows reading.

VOLATILITY volatile (contents are lost when the device is powered off).

non-volatile (contents are retained even when the device is powered off).

TYPES static RAM and dynamic RAM.

PROM, EPROM and EEPROM.

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CONCLUSION:A RAM looks like a bunch of registers connected together, allowing users to select a particular address to read or write.By providing a general interface, it’s easy to connect RAMs together to make “longer” and “wider” memories.

REFERENCES:[1].`Hynix produces its first DDR4modules` -by Graham Smith, Darien. .[2].`Next-Generation DDR4 Memory to Reach 4.266 GHZ`-by Kingston

technology.

[3].`The DRAM Story`-by ieee.org, 2008.01/10/2013



Software

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