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