Memory Computer Service and Repair Chapter 6 Ch 61

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 62

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 63

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 64

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 65

Physical Memory Packages Single 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 66

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 67

Physical Memory Packages Small Outline DIMM (SO- DIMM): Small outline packages of DIMM used for Laptops MicroDIMM: is a more compact version of SO-DIMM Ch 68

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 69

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 610

Types of RAM Double Data Rate – SDRAM Doubles the rate of SDRAM – DDR1 2.5 volts – DDR2 1.8 volts – DDR3 1.5 volts – DDR3L 1.35 v – DDR3U 1.25 V – Lower voltage offset higher frequency to manage heat Ch 611

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 612

Identifying Memory Ch 613 Memory Package# of PINS SIM (old)30 SIM (newer)72 DIMM / RDRAM168 SDRAM /DDR1184 DDR2 & 3240 DDR4284 MicroDIMM172 SO-DIMM200

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 614

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 615

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 616

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 617

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 (tCL-tRCD-tRP-tRAS) (CAS-delay RAS&CAS-RAS-delay RAS) Ch 618

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 619

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 620

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 621

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 622

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 623

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 624

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 625

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 626

End of Chapter 6 Questions? Ch 627