Lesson3 Memories

8/9/2019 Lesson3 Memories

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MEMORIESMEMORIES


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MemoryMemory -- the area of a computer thatthe area of a computer thattemporarily holdstemporarily holds data that is waiting to bedata that is waiting to be

processed, stored, or outputprocessed, stored, or output

RAMRAM

ROMROM

VirtualVirtual


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DIMM, RIMM, and SODIMM, RIMM, and SO--RIMMRIMM

RAM is usually configured as aRAM is usually configured as aseries of DIPs soldered onto aseries of DIPs soldered onto a

small circuit board calledsmall circuit board called DIMMDIMM (Dual In(Dual In--line Memory Module)line Memory Module)

RIMMRIMM ((RambusRambus InIn--line Memoryline MemoryModule)Module) Used for processors faster than 1 GHzUsed for processors faster than 1 GHz

SOSO--RIMMRIMM (Small Outline(Small Outline RambusRambus InIn--line Memory Module)line Memory Module)


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SDRAM vs. DDRSDRAM vs. DDR

DIMMs for SDRAM and DDR areDIMMs for SDRAM and DDR aredifferent, and not physicallydifferent, and not physically

compatible. SDRAM DIMMs havecompatible. SDRAM DIMMs have168168--pins and run at 3.3 volts, whilepins and run at 3.3 volts, whileDDR DIMMs have 184DDR DIMMs have 184--pins and runpins and runat 2.5 volts.at 2.5 volts.


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DDRSDRAMDDRSDRAM

SDRAMSDRAM byby double pumpingdouble pumping (transferring(transferringdata on the rising and falling edges of thedata on the rising and falling edges of theclock signalclock signal) without increasing the clock) without increasing the clock

frequency.frequency. With data being transferred 64With data being transferred 64 bitsbits at aat a

time, DDR SDRAM gives a transfer rate oftime, DDR SDRAM gives a transfer rate of(memory bus clock rate)(memory bus clock rate) 2 (for dual rate)2 (for dual rate)

64 (number of bits transferred) / 864 (number of bits transferred) / 8(number of bits/byte). Thus with a bus(number of bits/byte). Thus with a busfrequency of 100frequency of 100 MHz, DDR SDRAM gives aMHz, DDR SDRAM gives amaximum transfer rate of 1600maximum transfer rate of 1600 MBMB

//ss..


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DDRSpecificationDDRSpecification

Standardname

Memoryclock

Cycletime

I/O busclock

Datatransferspersecond

JEDECstandardVDDQvoltage

Modulename

Peaktransferrate

DDR-200 100 MHz 10 ns[2] 100 MHz200Million

2.50.2V

PC-16001600MB

/s

DDR-266 133 MHz 7.5 ns 133 MHz266Million

2.50.2V

PC-21002100MB/s

DDR-333 166 MHz 6 ns 166 MHz333Million

2.50.2V

PC-27002700MB/s

DDR-400 200 MHz 5 ns 200 MHz400Million

2.60.1V

PC-32003200MB/s


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DDRSDRAMDDRSDRAM

DDR SDRAM for desktop computers,DDR SDRAM for desktop computers, DIMMsDIMMs,,have 184 pins (as opposed to 168 pins onhave 184 pins (as opposed to 168 pins onSDRAM, or 240 pins on DDR2 SDRAM), andSDRAM, or 240 pins on DDR2 SDRAM), and

can be differentiated from SDRAM DIMMscan be differentiated from SDRAM DIMMsby the number of notches (DDR SDRAM hasby the number of notches (DDR SDRAM hasone, SDRAM has two). DDR SDRAM forone, SDRAM has two). DDR SDRAM fornotebook computers,notebook computers, SOSO--DIMMsDIMMs, have 200, have 200pins, which is the same number of pins aspins, which is the same number of pins as

DDR2 SODDR2 SO--DIMMs.DIMMs. Chips and modules with DDRChips and modules with DDR--400/PC400/PC--32003200

standard have a nominal voltage of 2.6standard have a nominal voltage of 2.6 V.V.


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MDDRMDDR

MDDR is an acronym that someMDDR is an acronym that someenterprises use forenterprises use for Mobile DDRMobile DDR

SDRAM, a type of memory used inSDRAM, a type of memory used insome portable electronic devices, likesome portable electronic devices, likemobile phonesmobile phones,, handheldshandhelds, and, anddigital audio playersdigital audio players. While standard. While standard

DDR SDRAM operates at aDDR SDRAM operates at a voltagevoltage ofof2.5 V, MDDR operates at voltage of2.5 V, MDDR operates at voltage of1.8 V, which allows a reduced power1.8 V, which allows a reduced power

consumption.consumption.


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PC3200256MBDDRSDRAMPC3200256MBDDRSDRAM


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Corsair 512MB DDR2Corsair 512MB DDR2--533 PC2533 PC2--4200 DDR24200 DDR2

SDRAM CL4 240SDRAM CL4 240--pin DIMMpin DIMM


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DDR2SDRAMSDDR2SDRAMS

DDR2DIMMs are not designed to be

backward compatible with DDRDIMMs.

FasterDDR2DIMMs are compatible with

slowerDDR2DIMMs; however, the faster

module runs at the slower module's

speed.


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DDR3 RAMDDR3 RAM

With data being transferred 64With data being transferred 64 bitsbitsat a time per memory module, DDR3at a time per memory module, DDR3SDRAM gives a transfer rate ofSDRAM gives a transfer rate of(memory clock rate)(memory clock rate) 4 (for bus4 (for busclock multiplier)clock multiplier) 2 (for data rate)2 (for data rate) 64 (number of bits transferred) / 864 (number of bits transferred) / 8

(number of bits/byte). Thus with a(number of bits/byte). Thus with amemory clock frequency of 100memory clock frequency of 100 MHz,MHz,DDR3 SDRAM gives a maximumDDR3 SDRAM gives a maximum

transfer rate of 6400transfer rate of 6400 MBMB//ss..


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ROMROM

ROMROM: (Read Only: (Read OnlyMemory) NonMemory) Non--volatile:volatile:remembers data evenremembers data evenwithout power.without power.

Begins executing whenBegins executing whencomputer is initiallycomputer is initiallyturned on (booted)turned on (booted)

ROM BIOSROM BIOS: (Basic Input: (Basic Input--Output System) hasOutput System) hasinstructions that tell theinstructions that tell thecomputer how to accesscomputer how to accessthe disk drives, find thethe disk drives, find theoperating system, andoperating system, and

load it into RAM.load it into RAM.


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Virtual MemoryVirtual Memory

The computers ability to useThe computers ability to usethe hard disk to simulate RAMthe hard disk to simulate RAM

Occurs when available RAM isOccurs when available RAM is

running lowrunning low MultitaskingMultitasking oftenoften uses virtualuses virtual

memorymemory

The operating system movesThe operating system movesleastleast--used data to the hardused data to the harddrive to free RAM for anotherdrive to free RAM for anothertasktask


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TASK:TASK:

DDRDDR

DDR2DDR2

DDR3DDR3 SOSO--DDRDDR

MDDRMDDR

Brand & ModelBrand & Model

Bus clockBus clock

Module NameModule Name Standard NameStandard Name

TRTR

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