Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Memory Computer Service and Repair Chapter 6 Ch 6 1 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 2 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 memory 5. Memory specifics – pairs? Size match? Ch 6 3 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 4 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 5 Physical Memory Packages Dual in-line Package (DIP): Memory Chip that has one row of connections per side Single Inline Package (SIP): Memory chip that has single row of connections on one side Ch 6 6 Physical Memory Packages Single 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 7 Physical Memory Packages Small Outline DIMM (SODIMM): Small outline packages of DIMM used for Laptops MicroDIMM: is a more compact version of SO-DIMM Ch 6 8 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 9 Types of RAM GDDR: Graphic DDR used exclusively for modern video cards. These cards come standard with cooling fans SDRAM: Synchronous Dynamic RAM speed exceeds 100 MHz found on older video cards Ch 6 10 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 11 Types of RAM 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 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) Ch 6 12 Identifying Memory Memory 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 13 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 14 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 15 Physical Arrangements Five 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 16 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 17 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 18 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 19 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 20 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 21 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 22 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 23 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 24 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 25 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 26 End of Chapter 6 Questions? Ch 6 27