EET 450 - Advanced EET 450 - Advanced DigitalDigital

Chapter 4Chapter 4

Computer MemoryComputer Memory

MemoryMemory

Primary and Secondary StoragePrimary and Secondary Storage– Primary is part of main memoryPrimary is part of main memory

at one point, DISK, DRUM, or CORE at one point, DISK, DRUM, or CORE memory was used.memory was used.

– Secondary is an antiquated view of a Secondary is an antiquated view of a system, but usually refers to mass system, but usually refers to mass storage.storage.

Old technology included the use of punch Old technology included the use of punch card, tape or DISK/DRUM memorycard, tape or DISK/DRUM memory

MemoryMemory

Main memory in modern PC’s uses a Main memory in modern PC’s uses a volatile type of memoryvolatile type of memory– Semiconductor memory is the ruleSemiconductor memory is the rule

Non-Volatile memory is used for special Non-Volatile memory is used for special purpose functions within the PCpurpose functions within the PC– BIOSBIOS– CMOS - is battery backup version on non-CMOS - is battery backup version on non-

volatile memoryvolatile memory– EEPROM or FLASH memory EEPROM or FLASH memory

MeasurementMeasurement

Capacity of memory is based on Capacity of memory is based on the amount of digital information the amount of digital information that can be stored.that can be stored.– Bits/ Bytes/ NibblesBits/ Bytes/ Nibbles– WordsWords– Double WordsDouble Words– Quad WordsQuad Words– LineLine

Memory is used in modern based Memory is used in modern based on GRANULARITYon GRANULARITY– the smallest amount of memory that the smallest amount of memory that

can be addressedcan be addressed– Increased bus widths have Increased bus widths have

INCREASED the size of the smallest INCREASED the size of the smallest granule accessedgranule accessed

Pentium/Pentium Pro use eight-byte Pentium/Pentium Pro use eight-byte modules modules

TechnologiesTechnologies

Random Access MemoryRandom Access Memory– Dynamic MemoryDynamic Memory

Data InData Out

Static Memory - referred to as Static Memory - referred to as SRAM SRAM

Read Only Memory ROMRead Only Memory ROM– Mask ROM - older bios chipsMask ROM - older bios chips– PROM - ProgrammablePROM - Programmable– EPROM - Erasable Programmable ROMEPROM - Erasable Programmable ROM– EEPROM - Electrically Erasable PROMEEPROM - Electrically Erasable PROM– Flash MemoryFlash Memory

Where’s the MemoryWhere’s the Memory

Memory uses in a PCMemory uses in a PC

CPU

CACHE

L1

CACHE

L2

Main Memory

Mass StorageCache

Memory UseMemory Use

Storage of program information Storage of program information Storage of BOOT informationStorage of BOOT information

– program and settingsprogram and settings Storage of DATAStorage of DATA

Logical OrganizationLogical Organization

Real Mode Memory - Real Mode Memory - – legacy of the 8086 processorlegacy of the 8086 processor– 1 Mbyte address space1 Mbyte address space

base memorybase memory

Logical OrganizationLogical Organization

Protected Mode memoryProtected Mode memory– Provides the entire address space of Provides the entire address space of

the processorthe processor– 4 Gbytes +4 Gbytes +

Lower MemoryLower Memory– Legacy stuff againLegacy stuff again– < 640k - conventional DOS memory< 640k - conventional DOS memory

BIOS Data AreaBIOS Data Area– Vector Table - lower 1kVector Table - lower 1k

Upper MemoryUpper Memory– the upper 384k of memory address the upper 384k of memory address

spacespace– top 32K - ROM Bios memorytop 32K - ROM Bios memory

High MemoryHigh Memory– 64kB+16 bytes above Upper memory 64kB+16 bytes above Upper memory – address line A20 allows thisaddress line A20 allows this– a function of binary round-offa function of binary round-off

Frame Buffer memoryFrame Buffer memory– Part of video memoryPart of video memory

Shadow MemoryShadow Memory– Provides solution to slower ROM memory Provides solution to slower ROM memory

providing BIOS functions. providing BIOS functions. ROM memory is slower than fast RAM for a ROM memory is slower than fast RAM for a

variety of reasons - bus width, intrinsic speed, variety of reasons - bus width, intrinsic speed, etc.etc.

– BIOS is ‘shadowed’ into RAM at boot time, BIOS is ‘shadowed’ into RAM at boot time, allowing faster access to these functions.allowing faster access to these functions.

– Other ROM memory - controller cards, Other ROM memory - controller cards, video, etc may be shadowed.video, etc may be shadowed.

Cache MemoryCache Memory– provides the speed interface between provides the speed interface between

slower memory/devices and the faster slower memory/devices and the faster memory/devicesmemory/devices

System Resource MemorySystem Resource Memory– Memory allocated by ‘heaps’ Memory allocated by ‘heaps’ – older OS problems with release of older OS problems with release of

memory on program exit.memory on program exit.

Unified Memory ArchitectureUnified Memory Architecture– UMAUMA– maps main memory into video display maps main memory into video display

address space address space

PerformancePerformance

Memory SpeedMemory Speed– based on access speed of integrated based on access speed of integrated

circuitscircuits -12 is 120 nS memory, -12 is 120 nS memory,

– Must have faster memory than called Must have faster memory than called for by processor speed.for by processor speed.

– Bus interface may be the problem.Bus interface may be the problem.

CachingCaching

Cache Size - 1k Cache Size - 1k – 256 k most favored256 k most favored

Note: Celeron processor suffered Note: Celeron processor suffered severe performance penalties by severe performance penalties by failing to include Cache memoryfailing to include Cache memory

Cache PerformanceCache Performance– four sectionsfour sections

show cache hits for access to store a show cache hits for access to store a single line - one for each transfersingle line - one for each transfer

1-1-1-1 would be best1-1-1-1 would be best

Cache MappingCache Mapping– Direct MappedDirect Mapped

CACHE mapped to block of memoryCACHE mapped to block of memory

– Full associativeFull associative CACHE can be for any block of memoryCACHE can be for any block of memory very costly - complexvery costly - complex

– set-associativeset-associative sections of CACHE are direct mapped.sections of CACHE are direct mapped.

Burst-Mode CachesBurst-Mode Caches– blocks of data at a timeblocks of data at a time

Synchronous Burst Ram - SRAM Synchronous Burst Ram - SRAM (note acronym conflict)(note acronym conflict)

Pipelined burst SRAMPipelined burst SRAM

Cache consistency Cache consistency

Write-throughWrite-through Write-backWrite-back

Memory TypesMemory Types

Static Column RamStatic Column Ram Page-Mode RAM (FP)Page-Mode RAM (FP) Extended Data Out Memory (EDO)Extended Data Out Memory (EDO) Burst EDO DRAMBurst EDO DRAM Synchronous DRAMSynchronous DRAM Enhanced DRAMEnhanced DRAM Cached DRAMCached DRAM

Rambus DRAMRambus DRAM Multibank DRAMMultibank DRAM PC100 RAMPC100 RAM PC166/266/333/400 etc.PC166/266/333/400 etc.

Memory PackagesMemory Packages

DIPDIP SIPPSIPP SIMMSIMM

– 30 pin30 pin– 72 pin72 pin

DIMMDIMM– 168 pin168 pin

AssignmentAssignment

Complete Chapter on memoryComplete Chapter on memory Review ‘Tom’s Hardware Guide: Review ‘Tom’s Hardware Guide:

Ram Guide.Ram Guide. Research ‘other’ RAM packages Research ‘other’ RAM packages

that may be available.that may be available.