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”