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PC Maintenance: PC Maintenance: Preparing for A+ Preparing for A+
CertificationCertificationChapter 6: MemoryChapter 6: Memory
Chapter 6 ObjectivesChapter 6 Objectives
Differentiate between types of memoryDifferentiate between types of memory Understand how memory holds dataUnderstand how memory holds data Identify physical types of RAMIdentify physical types of RAM Explain how an OS uses RAMExplain how an OS uses RAM Differentiate between conventional, upper, Differentiate between conventional, upper,
expanded and extended memoryexpanded and extended memory Get RAM usage information in an OSGet RAM usage information in an OS
Types of MemoryTypes of Memory
Read-Only Memory (ROM)Read-Only Memory (ROM) Random Access Memory (RAM)Random Access Memory (RAM)
Dynamic RAM (DRAM)Dynamic RAM (DRAM) Static RAM (SRAM)Static RAM (SRAM)
Read-Only Memory (ROM)Read-Only Memory (ROM)
Non-volatileNon-volatile Types of ROM chips:Types of ROM chips:
Programmable ROM (PROM)Programmable ROM (PROM) Erasable Programmable ROM (EPROM)Erasable Programmable ROM (EPROM) Electrically Erasable Programmable ROM Electrically Erasable Programmable ROM
(EEPROM)(EEPROM)
Random Access Memory (RAM)Random Access Memory (RAM)
SRAMSRAM Non-volatileNon-volatile Examples: L1 and L2 cachesExamples: L1 and L2 caches
DRAMDRAM VolatileVolatile Examples: system RAM, video RAMExamples: system RAM, video RAM
How RAM Stores DataHow RAM Stores Data
Each chip has a grid of on/off capacitorsEach chip has a grid of on/off capacitors Each RAM chip’s grid has a width and Each RAM chip’s grid has a width and
depth, like a spreadsheetdepth, like a spreadsheet A A bankbank is a group of chips with a collective is a group of chips with a collective
width matching the buswidth matching the bus
11 00 11 11 00 00 11 11
00 11 11 11 00 11 11 00
11 11 00 00 11 11 00 00
11 00 11 00 11 00 11 11
How RAM Stores DataHow RAM Stores Data
Multiple chips combine their widths to Multiple chips combine their widths to match the width of the busmatch the width of the bus
What is a Stick of RAM?What is a Stick of RAM?
StickStick: A SIMM or DIMM that holds a group : A SIMM or DIMM that holds a group of chipsof chips
SIMMsSIMMs
Single Inline Single Inline Memory Modules Memory Modules (SIMMs)(SIMMs) 30-pin (8-bit)30-pin (8-bit) 72-pin (32-bit)72-pin (32-bit) Both are now Both are now
obsoleteobsolete
DIMMsDIMMs
Dual Inline Memory Modules (DIMMs)Dual Inline Memory Modules (DIMMs) 168-pin (64-bit)168-pin (64-bit) SDRAM synchronized with system busSDRAM synchronized with system bus DDR SDRAM is double the system bus speedDDR SDRAM is double the system bus speed
RIMMsRIMMs
Rambus Inline Memory Modules (RIMMs)Rambus Inline Memory Modules (RIMMs) 184-pin (64-bit)184-pin (64-bit) Faster than DIMMsFaster than DIMMs Up to 8X or more of the system bus speedUp to 8X or more of the system bus speed More expensive, less popularMore expensive, less popular Waning in popularityWaning in popularity
How Many Sticks Per Bank?How Many Sticks Per Bank?
SIMMsSIMMs Four 30-pin SIMMs make up a 32-bit bankFour 30-pin SIMMs make up a 32-bit bank One 72-pin SIMM makes up a 32-bit bankOne 72-pin SIMM makes up a 32-bit bank Two 72-pin SIMMs make up a 64-bit bankTwo 72-pin SIMMs make up a 64-bit bank
DIMMs and RIMMsDIMMs and RIMMs One 168-pin DIMM makes up a 64-bit bankOne 168-pin DIMM makes up a 64-bit bank One 184-pin RIMM makes up a 64-bit bankOne 184-pin RIMM makes up a 64-bit bank
RAM ParityRAM Parity
One-bit parity chip for error correctionOne-bit parity chip for error correction Primarily found on 72-pin SIMMs, now mostly Primarily found on 72-pin SIMMs, now mostly
obsoleteobsolete
Later variant Later variant was Error Code was Error Code Correction Correction (ECC) RAM(ECC) RAM
RAM SpeedsRAM Speeds
Fast Page Mode (FPM)Fast Page Mode (FPM) Speed measured in nanoseconds of delaySpeed measured in nanoseconds of delay Lower number is betterLower number is better
Synchronous Dynamic RAM (SDRAM)Synchronous Dynamic RAM (SDRAM) Speed synchronized with system busSpeed synchronized with system bus Measured in MHzMeasured in MHz Higher number is betterHigher number is better
Selecting RAMSelecting RAM
Physical size of the stick (number of pins)Physical size of the stick (number of pins) CapacityCapacity SpeedSpeed Refresh technologyRefresh technology ParityParity
Understanding Memory Understanding Memory AddressesAddresses
A logically assigned location in RAMA logically assigned location in RAM Described using hexadecimalDescribed using hexadecimal Width of address bus determines available Width of address bus determines available
addressesaddresses
The First MegabyteThe First Megabyte
640K Conventional Memory640K Conventional Memory Running Applications in Real-ModeRunning Applications in Real-Mode
360K Upper 360K Upper MemoryMemory Reserved Reserved
for system for system useuse
Expanded MemoryExpanded Memory
Developed for 80286 systemsDeveloped for 80286 systems EMS (Expanded Memory Specification)EMS (Expanded Memory Specification) Also called LIM memory (Lotus-Intel-Also called LIM memory (Lotus-Intel-
Microsoft)Microsoft)
Expanded MemoryExpanded Memory
Swaps data into and out of a 64K page Swaps data into and out of a 64K page frame in upper memoryframe in upper memory
Extended MemoryExtended Memory
Originally developed for 80386 systemsOriginally developed for 80386 systems Can be accessed directly by protected-Can be accessed directly by protected-
mode applicationsmode applications HIMEM.SYS required HIMEM.SYS required XMS (Extended Memory Specification) is XMS (Extended Memory Specification) is
the standardthe standard Still in use todayStill in use today
DOS Memory UsageDOS Memory Usage
Use the MEM commandUse the MEM command
DOS Memory UsageDOS Memory Usage
The The MEM /C | MEM /C | MORE MORE command command provides provides more more informationinformation
Windows Memory UsageWindows Memory Usage
Mostly automaticMostly automatic Check amount of Check amount of
RAM in System RAM in System PropertiesProperties
System InformationSystem Information
Virtual MemoryVirtual Memory
Windows Windows automatically automatically controls virtual controls virtual memory, but memory, but settings can be settings can be overriddenoverridden