Post on 23-Dec-2015
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Memory
Computer Service and Repair Chapter 6
Ch 6
Ch 6 2
Questions to Ask Before Upgrading Memory
• Memory is one of the easiest upgrades to a computer
• Improperly identified memory modules and improper installation can DECREASE PC performance
Ch 6 3
Questions to Ask Before Upgrading Memory
1. Compatibility – what type of memory works with this motherboard
2. Quantity – What is total amount of RAM desired are your adding or replacing RAM
3. Parity or non-parity?4. Speed – will chipset support frequency of
memory5. Memory specifics – pairs? Size match?
Ch 6 4
ROM and RAM Memory• Read Only Memory (ROM): Designed to store program
information in a permanent fashion. • ROM is nonvolatile - information is retained even when
power is removed from the system• Types of ROM– Mask ROM: info. Permanently burned onto chip– PROM: Programmable Chip Info burned in with PROM burner
(not reprogrammable)– EPROM: use Ultra violet light in “window” to erase info– EEPROM: electronically erasable (one bit at a time) and
reprogrammable– Flash ROM: like EEPROM but erases whole chip
Ch 6 5
ROM and RAM Memory
• Random Access Memory (RAM): Designed to temporarily store data and programs
• RAM can be erased and reloaded over and over
• RAM is volatile memory information is lost when data is removed from system
Ch 6 6
Physical Memory PackagesSingle Inline Package (SIP):Memory chip that has single row of connections on one side
Dual in-line Package (DIP):Memory Chip that has one row of connections per side
Ch 6 7
Physical Memory PackagesSingle in-line memory module (SIMM): memory module containing a row of DIP chips mounted on a circuit board
Dual in-line memory module (DIMM): Looks lie SIMM but edge connectors do not connect electronically
Ch 6 8
Physical Memory PackagesSmall Outline DIMM (SO-DIMM): Small outline packages of DIMM used for Laptops
MicroDIMM: is a more compact version of SO-DIMM
Ch 6 9
Types of RAM
DRAM: Basic dynamic RAM installed in older PCs
EDO DRAM: Extended Data Output faster than DRAM and can access and transfer in new data before the previous data is transferred out
Ch 6 10
Types of RAM
SDRAM: Synchronous Dynamic RAM speed exceeds 100 MHz found on older video cards
GDDR: Graphic DDR used exclusively for modern video cards. These cards come standard with cooling fans
Ch 6 11
Types of RAM
• Double Data Rate – SDRAM Doubles the rate of SDRAM– DDR1 operates @ 2.5 volts– DDR2 operates @ 1.8 volts– DDR3 operates @ 1.5 volts– DDR3L operates @ 1.35 v– DDR3U operates @ 1.25 V– Lower voltage offset higher
frequency to manage heat
Ch 6 12
Types of RAM
DDR4: Standard released in 2012 expected to hit market in 2014 designed to operate at 400MHz with a memory module frequency times 8 ( 8 times 400) (12.8 GB)
RDRAM: Rambus DRAM 800 MHz motherboard and CPU must support 400 MHz Front bus – must be installed in pairs uses heat spreader to help cool
Ch 6 13
Identifying MemoryMemory Package # of PINS
SIM (old) 30
SIM (newer) 72
DIMM / RDRAM 168
SDRAM /DDR1 184
DDR2 & 3 240
DDR4 284
MicroDIMM 172
SO-DIMM 200
Ch 6 14
Other Memory terms
• Cache temporary storage location for data. Data remains in cache until the bus system is ready to transfer it to another component. (Size of cache directly affects rate of transfer)
• Serial Presence Detects (SPD) is a technology that identifies the type of RAM installed on a computer
• Overclockers: not only overclock CPUs but also RAM (risk of overheating)
Ch 6 15
Installing RAM
• You simply insert the module and BIOS recognizes it.– Locate notch to orient memory module– Align notch with “key” in socket– Should fit snug but night tight– Do not force module– Modules are extremely sensitive to static– Wear static wrist strap
Ch 6 16
Physical ArrangementsFive DIMM arrangements:• Single-channel mode: (asymmetric mode) single Memory
module installed (if two installed speed will be based on slowest chip)
• Dual-channel mode: (interleaved mode) memory modules are installed in pairs almost doubles data rate to CPU chips should match for optimum performance
• Triple-channel mode: Like dual channel but used three channels to support memory access (2 module acts as Dual Channel; 1 module acts as single channel
Ch 6 17
Physical Arrangements
Five DIMM arrangements: (Cont’d)• Quad-Channel Mode: Supports four identical memory
modules. Greatly increased speed. Can be configures in triple, double or single mode.
• Flex Mode: Hybrid arrangement operates in both dual and single mode– i.e. a 2GB and 4GB DIMM are installed 2GB from each module
act as dual mode and remaining 2 GB of the 4 GB Module act as single mode
Ch 6 18
Matching RAM Characteristics• Memory Chip Speed: Measured in Nanoseconds(ns) one
billionth of a second.– Try match to existing speed– Faster chips will run at same speed of slower chips
• Latency time it takes to complete a memory find and read– Think of memory as a matrix of bins with row and columns– Row Address Selection (RAS) time it takes to start memory read– Column Address Select (CAS) time it takes to access exact
location in matrix after RAS• CAS 3 takes 3 clock signals before CAS completes read of memory
location • Latency 5 (measures CAS)• Latency 3-3-3-5 (tCL-tRCD-tRP-tRAS) (CAS-delay RAS&CAS-RAS-delay RAS)
Ch 6 19
Matching RAM Characteristics
• Buffered Chips: Buffer is used to temporarily store data before transferring it to a device
• DDR Prefetch Memory Buffer: Small buffer Prefetch is followed by a number and lower case n. (2n would hold 2 bit 4n would be twice as fast with 4 bit prefetch)
• Registered Memory is a memory module that incorporates a registry chip that synchronizes memory without depending on the mother board
Ch 6 20
Matching RAM Characteristics• Memory data Integrity: a 16 MB SIMM has 128 million
memory cells. Data corruption can come from many causes:– Voltage leaks– Electrical interference– Power surges– Static shocks– Cosmic rays
• Parity: add one bit (parity bit) to every byte, counts number of 1s in every byte if even parity bit is 0 if odd parity bit is 1– Problem with parity if 2 bits leak parity could be fooled
• Fake Parity: parity bit is permanently set to 1 thus always matches check doesn’t really check memory Check part number to see if they are fake.
Ch 6 21
Matching RAM Characteristics
• Error Correction Code: not only checks for corruption but can correct most errors– Corrects single bit errors– Used in high-end computers (servers)
• Single Sided (SS) memory chips are mounted on one side of the memory module
• Double Sided (DS) memory chips are mounted on both sides of the memory module
Ch 6 22
Flash Memory Device• Flash memory: solid state, reusable data storage
device that retains data when power is removed based off of EEPROM (hot swap)
• USB Flash Drives: data is flashed to EEPROM chip– Pen drive, thumb drive, micro drive, stick drive or jump drive
• Flash Memory Cards: Smart media, CompactFlash, memory stick or etc.
• Solid-State Disk (SSD) Basically a laptop hard drive made entirely of DRAM chips no moving parts
Ch 6 23
Memory Map Structure• Backward compatibility has affect memory
development• Early PCs could only access 1 MB of memory– Conventional Memory (640 kB) - application software– Upper Memory (384 kB) – video system, expansion cards,
and BIOS– High Memory (64 kB) – basic DOS – software driver OR
Kernel.– Extended Memory (4 GB originally, now 8GB to 128GB) –
modern operating systems and software• Theoretically 16 TB
Ch 6 24
Modes• Real Mode: designed on the DOS system of memory. When
operating in Real mode only first 1MB of memory is used• Protected Mode: includes all real mode plus extended
memory (DOS systems)• Safe Mode: used by technicians to describe starting the
computer in protected mode– Only loads minimal drivers– Limits memory to 1MB– No 32 or 64 bit drivers– If computer starts in safe mode –problem is probably software
related– Hit [F8] key repeatedly during the boot operation
Ch 6 25
Virtual Memory
• Virtual Memory: Using the hard drive to supplement physical RAM it is referred to as a Page file or swap file. – The use of virtual memory causes an overall drop
in system performance – Use of page files (lots of hard drive activity)is an
indication that system is running out of memory– Shut down software– More likely time to add RAM
Ch 6 26
Troubleshooting Memory• Windows Memory Diagnostic Tool:– Type mdsched into search– Must be a system administrator or equal
• Gold vs. Tin connectors– Edge connectors and expansion slot metal should match– Mismatched will oxides– Some oxidation can be removed by simply removing and replacing
memory module– Oxidation can destroy motherboard
• Heat: if system runs for a short time (20 min) then locks up check airflow over memory, remove dust, clean filters, heat spreader and fans
Ch 6 27
End of Chapter 6
Questions?