Free software for printing computer images: http://www.gadwin.com/printscreen/#What

 

 

RAM

April 11, 2006

 

What is memory in a computer (RAM)

http://www.webopedia.com/TERM/R/RAM.html

http://en.wikipedia.org/wiki/RAM

                    Random = not in sequence

                    Analogous to short term memory in humans

                    I will discuss type attached to MOBO as modules

                    Chips of digital switches which represent binary data

                    Turn off PC, data is lost; vs. ROM (read only)

                    More = Better (usually)

                    Data is stored in RAM for short term vs. long term in HD

                    Site where OS, programs and data (currently running) are reserved for quick access (vs. HD)

                    Relatively cheap

                    Easy to install

 

Types of RAM

                    Various types and speeds

                    Older used SIMM; installed as pairs; Fast Page mode or Extended Data Out (EDO)

                    Now most common used is DIMM; use gold contacts; few still use EDO

                    After deciding DIMM vs. SIMM, decide SDRAM (older), DDR (transmission twice per clock cycle) SDRAM or RDRAM

                    SDRAM runs up to 133MHz; DDR SDRAM runs from 266 MHz to 400 MHz; DDR2 SDRAM runs up to 670 MHz; RDRAM at 800 MHz

 

                    RAM is normally rated at its highest tested stable speed, first by the chip manufacturer in cycle time (measured in nanoseconds, abbreviated ns), then by the module producer in frequency (megahertz, or MHz). Because of the inverse relationship between cycle time and frequency, knowing the rated frequency for a single chip is as easy as inverting cycle time and moving the decimal place. For example, 200 MHz SDRAM would be equivalent to 5 ns, because 5 ns equals 0.005 microseconds, and 1 divided by 0.005 equals 200.

 

                    Double Data Rate (DDR) technology allows data to be transmitted twice per clock cycle, so DDR SDRAM with a 200 MHz clock rate actually has a 400 MHz data rate, and is referred to as DDR400. The naming convention for finished modules has become its bandwidth, with each module providing 64 data connections for 8 Bytes of data per transfer. A 400 MHz data rate multiplied by 8 Bytes per transfer provides 3,200 MB/s bandwidth, hence the name PC3200.

 

Laptop RAM: smaller; (small output) SO-DIMMs; 144 & 200 pins; DDR SDRAM technology; speeds of PC66, PC100 and PC133. 200 pin available in PC2100 (266MHz) and PC2700 (333MHz) speeds.

 

 

 

How to proceed on your PC

                    You need to know the best type that your MOBO can handle

                    Determine memory and speed required; can not mix types; sometimes you can mix speeds; speed much less important then the amount

                    Check manual, Belarc, Internet, local retailer e.g. Frys (remove module from PC)

                    How much RAM

                    Compatibility

                    Buy name brands with lifetime warranty. Beware of counterfeits and inferior discounted products!

                    Resources available to help in selection, Apacer, Corsair, Crucial, Kingston, Mushkin, PNY and Viking

                    http://www.crucial.com/index.asp Not Sure Which Memory Upgrade You Need

                    http://urlsnip.com/191366 Navigating the Memory Upgrade Jungle

                    http://www.crucial.com/install/dimm.asp#tools Installing a DIMM in your desktop