MEMORY. Periféricos e Interfaces 2009/2010. Marcin Jaz

Transcription

1 MEMORY Periféricos e Interfaces 2009/2010 Marcin Jaz

2 Contents 1. Memory basics 2. Types of RAM and performance 3. Memory modules 4. Installing RAM Upgrades 5. Troubleshooting memory

3 What's memory Office analogy: cabinet disk, desk memory Workspace for the computer's processor, working with copy of the file Temporary storage area Save data to disk before cut off electical power Often called RAM misleading (virtual RAM on hard disk, ROM)

4 Types of memory There are three main types of memory: ROM Read Only Memory DRAM Dynamic Random Access Memory SRAM Static Random Access Memory

5 Types of memory: ROM Read Only Memory it's difficult or impossible to write to As RAM is randomly accessible Can store data permanently or semipermanently Nonvolatile memory data remains after power is swithed off Ideal to put PC's startup instructions for boot

6 Types of memory: ROM (2) EEPROM Electrically Erasable Programmable ROM type of ROM Rewritable it's possible to update such ROM Form of flash memory Most frequently used type of ROM nowadays

7 Types of memory: DRAM It's versions used in the mayority of PC's as the main memory nowadays, inexpensive Dense more memory capacity than other types, a lot of transistors in small chip, 1GB=one bilion transistors Transistor reads charge state of capacitor, charged cell indicates 1

8 Types of memory: DRAM (2) Capacitors are constantly draining so they must be refreshed to not loose data Refreshing takes time of the processor (less than 1%) Memory controller industry-standard: every 15ms refresh This timing can be modified (soft errors) Power interruption or refreshing problems=errors

9 Types of memory: SRAM Cluster of six transistors for each bit Much lower in density, phisically larger chips (2MB would be 64MB of DRAM) More difficult to produce and expensive than DRAM No capacitors so no need of refreshing Much faster than DRAM Also needs electical power to store data

10 Types of memory: SRAM (2) No efficency in use as main memory With increase of processor's speed DRAM was too slow and here SRAM could help It's used as cache processor's memory needs can be anticipated and data can be preloaded into high-speed cache memory and directly feed processor; only in case of cache miss (lack of needed data in cache) it's needed to read from the main memory or lower level of cache

11 Contents 1. Memory basics 2. Types of RAM and performance 3. Memory modules 4. Installing RAM Upgrades 5. Troubleshooting memory

12 Types of RAM FPM DRAM Fast Page Mode DRAM EDO RAM Extended Data Out RAM SDRAM Synchronous DRAM DDR SDRAM Double Data Rate SDRAM DDR2 SDRAM

13 Types of RAM: FPM DRAM DRAM which supports paging and bursting technique Without paging: row and column selected, with: keeps row, changing column pages (few KB) Burst mode becouse of consecutive memory accesses after selecting one cell, next 3 adjacent can be accessed without addicional wait states; cycles access instead of without bursting Most 486 and Pentium systems from 1995 and earlier

14 Types of RAM: EDO RAM Modified form of FPM DRAM, Hyper Page mode Specially manufactured chips allow a timing overlap between successive accesses EDO because data output drivers are not turned off after removal of the column address start of next cycle Saving about 10 ns per cycle, burst mode , in fact 5 % increase of speed From 1995 to 1997 supported

15 Types of RAM: SDRAM Delivers information in high speed bursts using synchronization with the motherboard clock Burst access , 20% faster than EDO Starting from 1996, most popular in 2001

16 Types of RAM: DDR SDRAM JEDEC-created standard, evolution of SDRAM Data transfered two times faster than in SDRAM, because it's being transfered twice per cycle: at the falling and rising edge Supported since 2001 mainstream memory technology until 2006

17 Types of RAM: DDR2 SDRAM Faster version of DDR SDRAM Higher clock speed, up to 1000MHz, previous version up to 400MHz Faster signaling without noise and interferece problems Lower voltage, power consumption and heat generation reduced Production since 2003, significant support since 2006

18 Contents 1. Memory basics 2. Types of RAM and performance 3. Memory modules 4. Installing RAM Upgrades 5. Troubleshooting memory

19 What's memory module It's a broad term used to refer to a series of DRAM integrated circuits Orginally memory was installed via individual chips (DIP dual inline package), problems: creep out of sockets, if soldered difficult to remove in case of going bad Memory module more chips treated as one, soldered to the module, which is pluged into special connectors on a motherboard or memory card

20 SIMM Single Inline Memory Module Two main types: 30 pin (8 bits plus an option for 1 additional parity bit) and 72 pins (respectively 32 plus 4) Used from 80s to the late 90s, then became obsolete

21 SIMM 30-pin (top) and 72-pin (bottom) SIMM's

22 DIMM Dual Inline Memory Module Different signal pins on each side of the module Standard DIMM have 168 pins, one notch on either side and two along the contact area DDR DIMM 184 pins, two notches on each side and offset notch along the contact area DDR2DIMM 240 pins, two notches on each side and one in the center of contact area

23 DIMM A 168-pin SDRAM module (top) and a 184-pin DDR SDRAM module (bottom).

24 Parity and ECC Parity bit can be added to every byte and is always chosen so that the sum of all 9 bits is stored as an odd number (odd parity); when the system reads checks this bit and if it's wrong there must by an error Parity bit Error Correcting Code allows a single bit error to be corrected, system can continue without interrupcion, implemented to correct one bit errors (98% of memory errors)

25 Contents 1. Memory basics 2. Types of RAM and performance 3. Memory modules 4. Installing RAM Upgrades 5. Troubleshooting memory

26 Installing RAM upgrades Most useful and least expensive upgrades that's possible to perform in your computer Add memory in the vacant slots or replace current memory with higher-capacity one Performance Monitor pages/second, commited and available bytes SIMM worst and more expensive than DIMM, older systems upgrade disadvantage

27 Contents 1. Memory basics 2. Types of RAM and performance 3. Memory modules 4. Installing RAM Upgrades 5. Troubleshooting memory

28 Testing memory POST Power On Self Test quickly done by BIOS when booting Boot from a DOS or diagnostic disk and run a true hardware diagnostic, can be running for days Dedicated memory test machine, eg. DIMM module tester, different speeds, voltages and timings It's vital to disable cache during tests

29 Memory errors Parity error change in memory since the data was originally storedco General or global protection fault program corrupted in memory Fatal exception error illegal instruction, invalid data, invalid privilege level Divide error division by 0 or result out of range Can be caused by defective or improperly configured memory, software bugs (drivers), bad power supplies ect.