1.06+Memory+Types,+Characteristics,+and+Purposes

Section 1.0 - Hardware toc include component="pageList" hideInternal="true" homeAtTop="on" limit="50"

SubSection 1.6 - Memory Types, Characteristics, and their Purposes

=Memory=
 * The hardware component that stores data as the CPU works with it
 * The memory is commonly called RAM(Random Access Memory)
 * RAM is implemented as computer chips occasionally soldered to the circuit board, but more often attached to a specialized socket
 * Memory is different from storage drives:
 * Storage refers to the locations where data is held in the long term
 * Data in storage remains there when your computer is turned off
 * Importance of RAM
 * Performance- Having more RAM almost always leads to improved computer performance. If you have insufficient RAM, the CPU must work harder shuffling data between RAM and the page file
 * Software Support- Many applications require a minimum amount of RAM. Having less RAM can prevent you from running these applications, or it could perform so bad that it will be unpleasant to use.
 * Memory types can be classified in various ways:
 * ==Volatile Memory==
 * Loses its contents when power isn't present
 * RAM is Volatile Memory
 * Its contents are lost when power is removed, even for a brief period
 * ==Non-Volatile Memory==
 * Doesn't lose its contents when power is removed
 * ==Types of Memory==
 * ===DRAM===
 * Dynamic RAM
 * Older technology
 * Sends the row address and then sends the column address to access a cell
 * The CPU must repeat this process for every cell
 * DRAM must be refreshed hundreds of times per second
 * Circuits using DRAM must include the components necessary to refresh its contents
 * ===SRAM===
 * Static RAM
 * Doesn't need to be refreshed
 * This memory holds its contents until power is removed
 * SRAM chips can be read more quickly than DRAM chips can
 * ===SDRAM===
 * Synchronous DRAM
 * Synchronized with the system clock to improve performance
 * Internal interleaving enables overlapped accesses
 * Returns data from a memory cell in a single cycle of the system clock
 * Faster than ADRAM and keeps pace with the rest of your computer better
 * Most modern computers use SDRAM for system memory
 * Must be capable of operating at your system's bus speed
 * ==Types of Data Rates:==
 * ===DDR[[image:http://upload.wikimedia.org/wikipedia/commons/thumb/1/1b/Desktop_DDR_Memory_Comparison.svg/220px-Desktop_DDR_Memory_Comparison.svg.png align="right" caption="Types of Data Rates" link="@http://upload.wikimedia.org/wikipedia/commons/thumb/1/1b/Desktop_DDR_Memory_Comparison.svg/220px-Desktop_DDR_Memory_Comparison.svg.png"]]===
 * Double Data Rate
 * Doubles the transfer rate by transferring data on both the rise and fall of the clock signal
 * Data Transfer range of 200-400 MHz
 * DDR Memory modules transfer data on a bus that is 64 data bits wide
 * ===DDR2===
 * Double Data Rate 2
 * Transfers data at a rate of 400-1066MHz
 * DDR2 Memory modules transfer data on a bus that is 64 data bits wide
 * ===DDR3===
 * Double Data Rate 3
 * Transfers data at a rate of 800-1600MHz
 * DDR3 Memory modules transfer data on a bus that is 64 data bits wide
 * ==Parity vs. Non-Parity==
 * ===Parity===
 * A scheme that enables the detection of an error
 * A bit is added to ensure that the number of bits with the value one in a set of bits is even or odd
 * ===Non-Parity===
 * Is regular memory
 * It contains exactly one bit of memory for every bit of data to be stored
 * ==ECC vs. Non-ECC (What's The Difference)==
 * ===ECC===
 * Error Correcting Code
 * Permits your computer not only to detect that an error has occurred, but also to correct that error
 * The computer can determine what was changed and what its original value was if it finds a error on it
 * ===Non-ECC===
 * Doesn't correct errors on your computer
 * ==Single sided vs. Double Sided==
 * ===Single Sided===
 * Early memory packages featured DRAM chips on just one side
 * The chips are a single group that are used simultaneously
 * Much faster than double sided RAM
 * ===Double Sided===
 * Has two groups of chips
 * The computers memory controller sees each of those two groups of chips separately
 * Can only read/write to one of them at a time
 * The controller must switch back and forth between chip groups
 * ==Single Channel vs. Dual Channel==
 * ===Single Channel===
 * Uses one 64-bit channel
 * ===Dual Channel===
 * Doubles data throughout from the memory to the memory controller by using two 64-bit data channels, giving you a 128-bit data path
 * Requires both a dual-channel-capable motherboard and two or more DDR, DDR2, or DDR3 memory modules
 * Increases bandwidth
 * ==Speeds==
 * ===PC100===
 * Standard for internal removable computer RAM
 * PC100 refers to Synchronous DRAM operating at a clock frequency of 100 MHz, on a 64-bit wide bus, and a voltage of 3.3 V
 * Available in 168-Pin DIMM and 144-Pin SO-DIMM form factors
 * Backward Compatible with PC66 and was superseded by the PC133 standard
 * ===PC133===
 * Computer Memory Standard
 * Refers to Synchronous DRAM
 * Operates
 * Clock Frequency of 133 MHz
 * 64-Bit Wide Bus
 * Voltage of 3.3 V
 * Available in 168 Pin DIMM and SO-DIMM form factors
 * Delivers a bandwidth of 1066 MB per second
 * Backward compatible with PC100 and PC66
 * ===PC2700===
 * Standard name is DDR-333
 * Operates
 * Clock Frequency of 166 MHz
 * 64-Bit Wide Bus
 * Voltage of 3.3 V
 * ===PC3200===
 * Other name for DDR-400
 * 3.2 GB per second Bandwidth
 * 200 MHz Bus Clock Speed