memory systems

Memory systems

Unit objectives: Describe the function of memory and

differentiate among various types of memory chips

Differentiate among the various memory packages

Install RAM into a system while handling it properly and meeting your PC’s installation requirements

Monitor memory usage Troubleshoot memory problems

Topic A

Topic A: Memory Topic B: Memory packaging Topic C: Memory installation Topic D: Memory monitoring Topic E: Memory troubleshooting

Memory

RAM: random access memory Working area for data during

processing Need sufficient RAM for

– Performance– Software support

Quality of RAM is important

Measuring memory

Cells– Store a single bit of data– 0 or 1– Represents on/off or yes/no

Measurement units – Bit– Nibble = 4 bits– Byte = 8 bits– Word = based on CPU

32-bit processor: 32-bit word 64-bit processor: 64-bit word

Larger memory units Byte (B) = 8 bits Kilobyte (KB) = 1024 bytes = 210 bytes Megabyte (MB) = 1024 KB = 220 bytes Gigabyte (GB) = 1024 MB = 230 bytes Terabyte (TB) = 1024 GB = 240 bytes

Memory types

Classify memory as:– Volatile vs. non-volatile– Static vs. dynamic– Asynchronous vs. synchronous

Volatile vs. non-volatile memory

Volatile: Loses contents without power Non-volatile: Keeps contents without power

RAM Volatile Random access memory

CMOS Volatile Complementary metal oxide semiconductor

ROM Non-volatile Read-only memory

PROM Non-volatile Programmable read-only memory

EPROM Non-volatile Erasable programmable read-only memory

EEPROM Non-volatile Electronically erasable programmable read-only memory

Flash Non-volatile

Dynamic vs. static memory

Dynamic (DRAM)– Must be continually refreshed– Inexpensive– Physically small chips

Static (SRAM)– Refreshing not required– More expensive– Larger– Faster

Typical uses– Main system memory: DRAM– Cache memory and CMOS: SRAM

Asynchronous vs. synchronous

Asynchronous– Not synchronized to system clock– Consistent time to access and read data

Synchronous– Synchronized to system clock– Accesses data and returns in one or

more clock cycles

SDRAM faster than ADRAM

Memory access typesDRAM Dynamic RAM Older technology

FPM Fast Page Mode Improved over DRAM

VRAM Video RAM Dual port, optimized for video

EDO Extended Data Out Improved over FPM

BEDO Burst Extended Data Out Adds pipelining to EDO

SDR SDRAM

Synchronous DRAM Interleaving permits overlapped requests

DRDRAM Direct Rambus DRAM 16-bit memory bus and two transfers per clock cycle

continued

Memory access types, continuedDDR SDRAM

Double Data Rate Double transfer rate of SDR SDRAM with two transfers per clock cycle

DDR2 SDRAM

Double Data Rate 2 Double transfer rate of DDR SDRAM with four transfers per clock cycle

DDR3 SDRAM

Double Data Rate 3 Double transfer rate of DDR2 SDRAM with eight transfers per clock cycle

Access time

Latency Memory speed

– Nanoseconds vs. megahertz

Overall speed– Doesn’t include latency

Bandwidth

Speed ratings

Activity A-1

Identifying memory characteristics

Topic B


Packaging Early PCs used individual DRAM chips

continued

Packaging, continued

Package– Small circuit board– More commonly called a module– Installed in slot

Module contains– Memory chips– Connecting wires– Support chips– Pins or edge contacts

Single- and double-sided modules

Early DRAM had chips on just one side

Double memory by placing chips on both sides

Double-sided modules have two rows of pins at bottom– Pins on front aren’t connected to pins on

back

Number of chips no longer has a 1:1 chip-to-bit limit

Package types

SIMM 30-pin – ADRAM

SIMM 72-pin – ADRAM

DIMM 168-pin – SDR SDRAM

DIMM 184-pin – DDR SDRAM

DIMM 240-pin – DDR2– DDR3

RIMM– 184-pin – 16-bit– 232-pin – 32--bit

continued

Package types, continued

MicroDIMM 144-pin SODIMM 144-pin – SDR SDRAM

SODIMM 200-pin– DDR– DDR2

SODIMM 204-pin – DDR3 SDRAM

Modules and chips

PC100 and PC133 use SDRAM PC1600, PC2100, PC2700, and

PC3200 use DDR SDRAM PC2-3200, PC2-4200, PC2-5300,

PC2-6400, and PC28500 use DDR2 SDRAM

PC3-6400, PC3-8500, PC3-10600, and PC3-12800 use DDR3 SDRAM

Memory error recovery

Parity — Detects an error– Even– Odd– Mark– Space

ECC — Detects and corrects an error Desktop memory — No parity or ECC Server memory — Often includes

parity or ECC

Parity

9 chips,supportsparity

8 chips,no parity

Activity B-1

Comparing RAM packaging

Topic C


Memory installation considerations

Banking requirements Proper handling techniques Slot insertion techniques Safe storage BIOS configuration

Banking requirements

Install memory in groups called banks Bank might include 1, 2, or 4 slots Must fill every slot in a bank Might have to use same type and

speed of memory in every slot Leave extra banks empty

– With DRDRAM, install continuity modules

Dual-channel architecture

Proper handling

Unplug computer before opening it Dissipate static Move around as little as possible Always handle modules by their edges

Inserting memory modules

SIMM1. Insert module at 45-degree angle2. While pushing into slot, move module

to fully vertical or horizontal position. Clips should engage automatically when module is fully seated

DIMM1. Spread retaining clips before insertion2. Insert the module straight into the slot,

perpendicular to the motherboard3. Push firmly until the retaining clips

snap into place on either side

Removing a module

SIMM1. Gently release the retaining clips at

both ends of the module2. Move the module to a 45-degree angle

if it doesn’t do so automatically3. Remove the module

DIMM1. Release the retaining clips on both

ends of the module2. Remove the module by pulling it

straight up from the slot

CMOS configuration

BIOS checks memory at boot Compares actual memory with CMOS

entry Follow prompt to update CMOS entry

Activity C-1

Adding memory to a desktop computer

Notebook memory

Location varies from notebook to notebook

Refer to documentation Shut down notebook, unplug cord, and

remove battery

Shared video memory

Main system memory shared with video circuitry– No dedicated video memory

Reduces cost Uses less power; generates less heat Not all RAM is available to OS and

applications (does not show as present)

Slower than dedicated video memory Add more system memory to increase

performance

Activity C-2

Adding memory to a notebook computer

Memory in handheld computers

Expandable memory, a feature of more expensive handhelds

Some use modules similar to those in notebooks

Most use memory cards similar to those in digital cameras

Have a slot for inserting a flash memory card

Consult the manual

Activity C-3

Adding memory to a handheld computer

Topic D


Task Manager

Windows GUI utility Provides information on processes running Version available in all Windows OSs

– Windows 9x/Me Program List – Windows NT/2000/XP/Vista/7 Task Manager

Access:– Ctrl + Alt + Delete – Right-click empty space in the taskbar and

choose Task Manager – Ctrl + Shift + Esc

Performance tab indicators

CPU Usage CPU Usage History Memory (7/Vista) Physical Memory Usage History

(7/Vista) PF Usage (XP/2000) Page File Usage History (XP/ 2000)

continued

Performance tab indicators, continued

System (7/Vista) Totals (XP/2000) Physical Memory Commit Charge Kernel Memory Summary data

The Performance tab

Activity D-1

Monitoring memory usage

Virtual memory

Optimizing the page file

1. On boot partition by default

2. Determined by amount of RAM

3. Size automatically increases or decreases for best performance

4. Can manually override the settings

5. Page file size range:1. RAM × 1.5 to 3.0

2. System’s peak commit value

6. Can move file to different hard disk

Changing page file size

1. In Windows 7/Vista, click Start, right-click Computer, and choose PropertiesIn Windows 2000 /XP, right-click My Computer and choose Properties

2. In Windows 7/Vista, click Advanced system settingsIn Windows 2000/XP, activate the Advanced tab

3. In the Performance section, click Settings, and then activate the Advanced tab

4 In the Virtual memory section, click Change

5 Clear Automatically manage paging file size for all drives

6 Select Custom Size, and set the initial and maximum size

Activity D-2

Changing the size of the Windows page file

Topic E


Memory testing

POST not sufficient Use testing utility

– Memtest86 — Free, open source– Microsoft Windows Memory

Diagnostic — Free, unsupported

Boot from floppy or CD

Memory-related problems

201 BIOS error code at boot time Parity error message Computer randomly freezes (locks up)

or crashes Wrong amount of memory reported by

the BIOS Windows reports Page Fault or

Exception errors Random crashes, corrupted data,

strange application behavior

Activity E-1

Troubleshooting memory

Unit summary

Described the function of memory and differentiated among various types of memory chips

Differentiated among the various memory packages

Installed RAM into a system while handling it properly and meeting your PC’s installation requirements

Monitored memory usage Resolved memory problems

memory systems

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