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 = 2 10 bytes Megabyte (MB) = 1024 KB = 2 20 bytes Gigabyte (GB) = 1024 MB = 2 30 bytes Terabyte (TB) = 1024 GB = 2 40 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 RAMVolatile Random access memory CMOSVolatile Complementary metal oxide semiconductor ROMNon-volatile Read-only memory PROMNon-volatile Programmable read-only memory EPROMNon-volatile Erasable programmable read- only memory EEPROMNon-volatile Electronically erasable programmable read-only memory FlashNon-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 types DRAMDynamic RAMOlder technology FPMFast Page ModeImproved over DRAM VRAMVideo RAMDual port, optimized for video EDOExtended Data OutImproved over FPM BEDOBurst Extended Data OutAdds pipelining to EDO SDR SDRAM Synchronous DRAMInterleaving permits overlapped requests DRDRAMDirect Rambus DRAM16-bit memory bus and two transfers per clock cycle continued

Memory access types, continued DDR SDRAM Double Data RateDouble transfer rate of SDR SDRAM with two transfers per clock cycle DDR2 SDRAM Double Data Rate 2Double transfer rate of DDR SDRAM with four transfers per clock cycle DDR3 SDRAM Double Data Rate 3Double 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 Topic A: Memory Topic B: Memory packaging Topic C: Memory installation Topic D: Memory monitoring Topic E: Memory troubleshooting

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, PC , and PC 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, supports parity 8 chips, no parity

Activity B-1 Comparing RAM packaging

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

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 SIMM 1.Insert module at 45-degree angle 2.While pushing into slot, move module to fully vertical or horizontal position. Clips should engage automatically when module is fully seated DIMM 1.Spread retaining clips before insertion 2.Insert the module straight into the slot, perpendicular to the motherboard 3.Push firmly until the retaining clips snap into place on either side

Removing a module SIMM 1.Gently release the retaining clips at both ends of the module 2.Move the module to a 45-degree angle if it doesn’t do so automatically 3.Remove the module DIMM 1.Release the retaining clips on both ends of the module 2.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 Topic A: Memory Topic B: Memory packaging Topic C: Memory installation Topic D: Memory monitoring Topic E: Memory troubleshooting

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 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 Properties In Windows 2000 /XP, right-click My Computer and choose Properties 2.In Windows 7/Vista, click Advanced system settings In Windows 2000/XP, activate the Advanced tab 3.In the Performance section, click Settings, and then activate the Advanced tab 4In the Virtual memory section, click Change 5Clear Automatically manage paging file size for all drives 6Select Custom Size, and set the initial and maximum size

Activity D-2 Changing the size of the Windows page file

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

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