Memory

1
Memory

• Terms and Definitions

2
Chapter Objectives

• After completing this chapter you will
• Understand memory-related terminology.
• Be able to install and remove memory chips.
• Understand how memory works with different
  operating systems.
• Be able to optimize memory under different
  operating systems.
• Be able to troubleshoot memory problems.

3
Memory Overview

• Types of Memory
• RAM (Random Access Memory) is volatile memory
  found on the motherboard and stores the operating
  system, the software applications, and the data
  being used by all of the software.
• ROM (Read Only Memory) is a non-volatile type of
  memory that keeps data in chips even when the
  computer is shut off.
• Types of RAM
• DRAM (Dynamic RAM) is less expensive, but slower
  than SRAM. It requires periodic refreshing of
  the electrical charges holding the 1s and 0s.
• SRAM (Static RAM) is faster but more expensive
  than DRAM. It is also known as cache memory or
  L2 cache.

4
Memory Overview

• Memory Terms
• Refreshing Periodically rewriting information
  to the memory chip.
• Nanosecond A billionth of a second.
• Pipelining The process by which microprocessors
  and memory obtain computer software instructions
  in a timely fashion.
• Cache Memory also known as SRAM can be found
  on the motherboard, but normally is found inside
  the CPU. Cache memory holds the most frequently
  used data so the CPU does not return to the
  slower DRAM chips to obtain the data.

5
Memory Physical Packaging

• Types of Memory Packaging
• DIP (Dual In-line Package) A chip that has a
  row of legs running down each side.
• SIMM (Single In-line Memory Module) Available
  in 30-pin and 72-pin configurations.
• DIMM (Dual In-line Memory Module) 168-pin
  configuration and used in Pentium, Pentium Pro,
  Pentium II or Pentium III motherboards.
• DDR DIMM 184-pin configuration and used in AMD
  Athlon computers, Pentium 4 computers, and
  high-end servers.
• RIMM Type of memory module used on video
  adapters and future motherboards.

6
Memory Physical Packaging

• Methods of Error Checking
• Parity A method for checking the accuracy of
  data going in or out of the memory chips.
• Non-parity Memory chips that do not use any
  error checking.
• ECC (Error Correcting Code) Uses a mathematical
  algorithm to detect up to four-bit memory errors
  and correct one-bit memory errors.
• A computer system that uses parity must have
  parity memory installed.

7
Memory Physical Packaging
Memory Chips
Memory Figure 1
8
Memory Physical Packaging
184-Pin DDR DIMM and RIMM
Memory Figure 2
9
Memory Chip Capacity

• Most Common Memory Capacity
• DIP chips
• 64Kb, 256Kb, or 1MB
• 30-Pin SIMM Modules
• 256Kb, 512Kb, 1MB, 2MB, and 4MB
• 72-Pin SIMM Modules
• 4MB, 8MB, 16MB, 32MB, 64MB, and 128MB
• DIMM Modules
• 8MB, 16MB, 32MB, 64MB, 128MB, 256MB, 512MB, and
  1024MB
• RIMM Modules
• 64MB, 128MB, and 256MB

10
Identifying Chip Capacity and Speed

• The only way to be certain of the capacity is to
  install the SIMM in a computer or research the
  manufacturers number on the internet.
• Access Time How fast information goes into a
  memory chip or is removed from the chip.
• The lower the number of nanoseconds, the faster
  the access time of the memory chips.

11
Identifying Chip Capacity and Speed
Chip Capacity
Memory Figure 3
12
Identifying Chip Capacity and Speed
Memory Chip Access Time
Memory Figure 4
13
Memory Chip Technologies

• Technology to provide faster DRAM speeds
• FPM (Fast Page Mode)
• EDO (Extended Data Out)
• BEDO (Burst EDO)

14
Memory Chip Technologies

• SDRAM (Synchronous DRAM) provides very fast burst
  memory access by placing new memory address on
  the address bus before prior memory address
  retrieval and execution completes.
• The PC100 SDRAM DIMMs are designed for the 100MHz
  front side bus.
• The PC133 SDRAM DIMMs are designed for the 133MHz
  front side bus, but will work with the 100MHz
  motherboards.
• SPD (Serial Presence Detect) is an extra EEPROM
  feature of SDRAM DIMM PC100 and PC133 standard
  that adjusts the motherboard timings for the best
  CPU and RAM performance.
• Registered SDRAM or Buffered SDRAM delays all
  data transfers by one clock to ensure accuracy.
  It is used in network servers and higher end
  computers.
• Unbuffered SDRAM is the memory type most often
  used in home computers and in low-to-medium
  powered computers.
• VCM (Virtual Memory Channel) is a memory chip
  alternative to SDRAM that fits in DIMM slots.
  The motherboard chipset must support it.

15
Memory Chip Technologies

• Other Types of RAM
• RDRAM (Rambus DRAM) Developed by Rambus, Inc.
  and used in Pentium 4 computers and some video
  adapters. RDRAM is packaged in RIMMs.
• When RIMMs are used, all memory slots must be
  filled. Put an C-RIMM (Continuity RIMM), which
  is a blank RIMM, in any empty slot.
• DDR RAM (Double Data Rate RAM) also called DDR
  SDRAM Data can be transmitted on both sides of
  the clock signal (rising and falling edges).
• VRAM (Video RAM) A type of memory found on a
  video card.
• WRAM (Windows RAM) Dual-ported memory found on
  video adapters.
• SGRAM (Synchronous Graphic Random Access Memory)
  Used on video adapters and graphics
  accelerators and have special memory techniques
  that speed up graphics-intensive functions.

16
Memory Chip Technologies
Memory Table 2
17
Memory Banks

• Bank or Memory Bank is one or more memory chips
  that work together to transfer data to and from
  the CPU and a device.
• External Data Lines or External Data Path is the
  electronic lines that allow the microprocessor to
  communicate with external devices.
• Parity Chip is a memory chip on a memory bank
  that checks for data accuracy.

18
Memory Banks
8088 Memory Banks
Memory Figure 6
19
Memory Banks
80386 Memory Banks
Memory Figure 7
20
Buying the Right 72-Pin SIMM

• Purchasing the correct memory can be difficult.
  Advertisements for memory can often be confusing
  and even misleading. Always refer to your
  motherboard documentation for the correct type of
  memory to install with your computer.

21
Buying the Right 72-Pin SIMM
Sample of 72-Pin SIMM Advertisements
Memory Figure 8
22
Populating Pentium and Higher Motherboards

• Computers with a Pentium processor and SIMM
  sockets have two SIMMs that must be installed in
  one bank for the computer to operate.
• Pentium Pro computers usually have one DIMM
  socket as a bank and two 72-Pin SIMM sockets for
  another bank of memory.
• Pentium 4s ship with DIMM or RIMM sockets.

23
Populating Pentium and Higher Motherboards
Pentium Memory Banks
Memory Figure 9
24
Populating Pentium and Higher Motherboards
Pentium
Memory Figure 10
25
Buying the Right DIMM or RIMM

• Be careful with purchasing DIMMs and always refer
  to the documentation.
• DIMM Terminology
• CAS (Column Address Strobe) Latency is the amount
  of time that passes before the processor moves on
  to the next memory address.
• RAS (Row Address Strobe) is a signal that selects
  a specific memory row.

26
Buying the Right DIMM or RIMM
Sample 168-Pin DIMM Advertisements
Memory Figure 11
27
Buying the Right DIMM or RIMM
Sample DDR RAM DIMM and RIMM Advertisements
Memory Figure 12
28
Memory Installation Rules

• When you start a bank, fill a bank.
• Use memory chips of the same capacity in a memory
  bank.
• All the chips in a bank should have the same
  access speed, if possible.
• All the chips in a bank should be of the same
  type, if possible.
• Some manufacturers require that higher capacity
  chips be placed in the first bank.
• Always refer to the motherboard documentation for
  memory installation requirements.

29
Same Capacity Chips in Bank

• Memory chips in a bank must work together. Each
  chip in the bank must hold the same number of
  bits as the other chips.
• Two SIMM sockets require two equal capacity SIMMs
  to be installed.
• Always refer to the motherboard documentation for
  installation requirements.

30
Laptop Memory

• Types of Laptop Memory
• SO-DIMM (Small Outline-DIMM) Special, smaller
  DIMM used in laptop computers.
• SO-RIMM (Small Outline-RIMM) Special, smaller
  RIMM used in laptop computers.

31
Flash Memory

• Flash Memory is a type of non-volatile memory
  that holds data even when the computer power is
  off.
• It is used with laptops because it is small,
  fast, and consumes little power.
• PCs use flash memory as a replacement for the
  BIOS chip.
• CompactFlash (CF) is a small 50-pin removable
  storage device that allows speeds up to 16 MBps
  CF has two main standards, CompactFlash and CF
• SmartMedia A trademark of the Toshiba
  Corporation and is used in a variety of devices
  such as cameras, PDAs, musical instruments,
  printers, faxes, MP3 players, and scanners.
  There are two versions of SmartMedia cards 3.3V
  and 5V.
• USB flash drives also called a memory stick
  allows storage up to 1 GB with higher capacities
  expected.

32
Installing Memory Chips

• Installation Steps
• Determine which chip capacities can be used for
  the system.
• Determine how much memory is needed.
• Determine what capacity chips go in each bank.
• Before removing or installing memory chips,
  always refer to the documentation for you
  computer.
• Use an anti-static wrist strap when removing or
  installing memory chips.

33
Removing a DIMM/RIMM

• To remove a DIMM or a RIMM, push down on the
  outside edges of the DIMMs retaining tabs. The
  DIMM/RIMM lifts slightly out of the socket.

34
Removing a DIMM/RIMM
DIMM/RIMM Removal
Memory Figure 17
35
Installing a DIMM/RIMM

• To install a DIMM or RIMM, align the notches on
  the DIMM/RIMM with the socket and press down
  until the tabs close on the memory module.
• The following concepts summarize the most
  important memory installation steps
• Always refer to the motherboard or computer
  documentation before purchasing or installing
  memory.
• Install SIMMs into Pentium or higher computers in
  groups of two.
• When installing DIMMs, install one DIMM per bank.
• When installing RIMMs, install one RIMM per bank
  and fill the empty banks with C-RIMMs.
• When installing PC100 and PC133 SDRAM DIMMs,
  install one DIMM per bank.
• When installing DDR SDRAM DIMMs, insert one DIMM
  per bank.

36
Installing a DIMM/RIMM
DIMM/RIMM Installation
Memory Figure 21
37
Configuring the Computer

• After memory has been installed in a computer,
  changes to the CMOS Setup are required to
  recognize the new memory.
• The memory count during POST should equal the
  amount of memory installed.

38
How Much Memory?

• The amount of memory that can be installed on the
  motherboard depends on two things the
  motherboard manufacturer and the microprocessor.
• Memory Modes
• Protected Mode allows applications to access
  memory above 1 MB. Applications must be
  specifically written for protected mode in order
  to use it.
• Real Mode Early computers that could not access
  memory above 1 MB. Most DOS applications were
  written for real mode microprocessors.
• Memory Map is a graphical representation of the
  amount of a microprocessors memory addresses.
• UMA (Upper Memory Area) or Reserved Memory Area
  is an area of the memory map between 640K and 1
  MB that was traditionally reserved for ROM chips.
  Unused portions of UMA can be made into upper
  memory blocks.

39
How Much Memory?
Intel Microprocessor Address Lines
Memory Table 3
40
How Much Memory?
8088 Memory Map
Memory Figure 22
41
How Much Memory?
Memory Map for 80386 through Pentium
Memory Figure 23
42
Memory and Software Considerations

• Whether or not an application can use all of the
  RAM in the computer depends on the operating
  system installed on the computer and the
  operating system that the application was written
  for.
• An application specifically written for the
  DOS/Windows environment running on a system with
  Windows 9x, NT, 2000, or XP behaves as if it was
  installed on a system with DOS.
• An application specifically written for Windows
  NT/2000/XP will not work in a Windows 9x or
  DOS/Windows 3x environment.

43
DOS/Windows 3.X and Memory
8088 Memory Map
Memory Figure 24
44
Conventional Memory

• Conventional Memory is the area from 0 to 640K.
  DOS and all DOS applications written for the 8088
  computers ran in conventional memory.
• Upper Memory Area or Reserved Memory is the area
  of the memory map between 640K and 1MB that was
  traditionally reserved for ROM chips.
• EMS (Expanded Memory Specification) or Expanded
  Memory or LIM (Lotus, Intel, Microsoft) Memory is
  a 64KB space in the memory map normally reserved
  for ROM chips that allows paging up to 32MB of
  memory, 64KB at a time.

45
Expanded Memory
Expanded Memory
Memory Figure 25
46
Extended Memory

• XMS (Extended Memory Specification) or Extended
  Memory is the area of the microprocessors memory
  map above 1 MB.
• For a system to use Extended Memory, the driver
  HIMEM.SYS must be installed in the CONFIG.SYS
  file or automatically by the Windows operating
  system.

47
Extended Memory
80386, 80486, and Pentium Memory Map
Memory Figure 26
48
Adding More Cache/RAM

• Adding more RAM can make a noticeable difference
  in the performance of a computer. For todays
  computer, it is recommended to have at least
  128MB of RAM.
• Disk Cache is a portion of RAM set aside for hard
  drive data that speeds up hard drive operations.
• Windows 9x, NT, 2000, and XP have an integrated
  caching program for CD and DVDs.

49
Windows 9X/NT/2000/XP Disk Caching

• Windows 98, NT, and 2000 have efficient memory
  management through the VMM (Virtual Memory
  Manager).
• Virtual Memory is a method of using the hard disk
  space as RAM.
• Swap File is a block of hard drive space used
  like RAM by applications.
• Pages 4KB blocks of memory that the memory
  space is divided into.

50
Windows 9X/NT/2000/XP Disk Caching
Windows 98/NT/2000/XP Virtual Memory Usage
Memory Figure 27
51
Monitoring Memory Usage Under Windows

• Each of these Windows utilities evaluate
  different performance areas the file system, the
  IPX/SPX compatible protocol, the kernel, the
  memory manager, and Microsoft Network Monitor
  Performance Data.
• System Monitor is used with Windows 9x
• Performance Monitor is used with Windows NT
• Performance Utility is used with Windows 2000
• Thread is a unit of programming code that
  receives a slice of time from Windows so it can
  run concurrently with other units of code.

52
Using a RAM Drive

• A RAM Drive is a virtual hard disk drive created
  from RAM. It is the opposite of virtual memory.
• Most DOS applications run fine under Windows 9x,
  but those with problems can be run in the Windows
  9xs MS-DOS mode.
• DOS applications run in an NT/2000/XP process
  called NTVDM (NT Virtual DOS Machine). The NTVDM
  process simulates a 486 computer running DOS.

53
Troubleshooting Memory Problems

• The following tips help with memory management
• Add more RAM to help with performance
• Adjust virtual memory size
• Turn off the screen saver
• Remove the desktop wallpaper scheme or use a very
  plain one
• Put the swap file on the fastest hard drive
• Do not put the swap file on multiple partitions
  that reside on the same hard drive
• Put the swap file on a hard disk partition that
  does not contain the operating system
• Adjust your Temporary Internet Files setting
• Defragment the hard drive
• Remove unnecessary files and applications from
  the hard drive
• Empty the Recycle Bin