RAM Types
DRAM
Dynamic RAM is a memory chip that is used as main memory. DRAM must be constantly refreshed with pulses of electricity in order to maintain the data stored within the chip.
SRAM
Static RAM is a memory chip that is used as cache memory. SRAM is much faster than DRAM and does not have to be refreshed as often. SRAM is much more expensive than DRAM.
SDRAM
Synchronous DRAM is DRAM that operates in synchronization with the memory bus. The memory bus is the data path between the CPU and the main memory. Control signals are used to coordinate the exchange of data between SDRAM and the CPU.
DDR SDRAM
Double Data Rate SDRAM is memory that transfers data twice as fast as SDRAM. DDR SDRAM increases performance by transferring data twice per clock cycle.
DDR2 SDRAM
Double Data Rate 2 SDRAM is a faster than DDR-SDRAM memory. DDR2 SDRAM improves performance over DDR SDRAM by decreasing noise and crosstalk between the signal wires.
DDR3 SDRAM
Double Data Rate 3 SDRAM expands memory bandwidth by doubling the clock rate of DDR2 SDRAM. DDR3 SDRAM consumes less power and generates less heat than DDR2 SDRAM.
RDRAM
RAMBus DRAM is a memory chip that was developed to communicate at very high rates of speed. RDRAM chips are not commonly used.
Early computers had RAM installed on the motherboard as individual chips. The individual memory chips, called dual inline package (DIP) chips, were difficult to install and often became loose. To solve this problem, designers soldered the memory chips on a special circuit board to create a memory module. The different types of memory modules :
DIP
Dual Inline Package is an individual memory chip. A DIP has dual rows of pins used to attach it to the motherboard.
SIMM
SIMM
Single Inline Memory Module is a small circuit board that holds several memory chips. SIMMs have 30-pin or 72-pin configurations.
DIMM Memory
DIMM Memory
Dual Inline Memory Module is a circuit board that holds SDRAM, DDR SDRAM, DDR2 SDRAM, and DDR3 SDRAM chips. There are 168-pin SDRAM DIMMs, 184-pin DDR DIMMs, and 240-pin DDR2 and DDR3 DIMMs.
RIMM
RIMM
RAMBus Inline Memory Module is a circuit board that holds RDRAM chips. A typical RIMM has a 184-pin configuration.
SODIMM
SODIMM
Small Outline DIMM has a 72-pin and 100-pin configurations for support of 32-bit transfers or a 144-pin, 200-pin, and 204-pin configurations for support of 64-bit transfers. This smaller, more condensed version of DIMM provides random access data storage that is ideal for use in laptops, printers, and other devices where conserving space is desirable.
NOTE: Memory modules can be single-sided or double-sided. Single-sided memory modules contain RAM only on one side of the module. Double-sided memory modules contain RAM on both sides.
The speed of memory has a direct impact on how much data a processor can process, because faster memory improves the performance of the processor. As processor speed increases, memory speed must also increase. For example, single-channel memory is capable of transferring data at 64 bits per clock cycle. Dual-channel memory increases the speed by using a second channel of memory, creating a data transfer rate of 128 bits.
Double Data Rate (DDR) technology doubles the maximum bandwidth of Synchronous Dynamic RAM (SDRAM). DDR2 offers faster performance and uses less energy. DDR3 operates at even higher speeds than DDR2. However, none of these DDR technologies are backward- or forward-compatible. Many common memory types and speeds :
Cache
Static RAM (SRAM) is used as cache memory to store the most recently used data and instructions. SRAM provides the processor with faster access to the data than retrieving it from the slower dynamic RAM (DRAM), or main memory. The three most common types of cache memory :
L1
NOTE: Memory modules can be single-sided or double-sided. Single-sided memory modules contain RAM only on one side of the module. Double-sided memory modules contain RAM on both sides.
The speed of memory has a direct impact on how much data a processor can process, because faster memory improves the performance of the processor. As processor speed increases, memory speed must also increase. For example, single-channel memory is capable of transferring data at 64 bits per clock cycle. Dual-channel memory increases the speed by using a second channel of memory, creating a data transfer rate of 128 bits.
Double Data Rate (DDR) technology doubles the maximum bandwidth of Synchronous Dynamic RAM (SDRAM). DDR2 offers faster performance and uses less energy. DDR3 operates at even higher speeds than DDR2. However, none of these DDR technologies are backward- or forward-compatible. Many common memory types and speeds :
Cache
Static RAM (SRAM) is used as cache memory to store the most recently used data and instructions. SRAM provides the processor with faster access to the data than retrieving it from the slower dynamic RAM (DRAM), or main memory. The three most common types of cache memory :
L1
L1 cache is internal cache and is integrated into the CPU.
L2
L2
L2 cache is external cache and was originally mounted on the motherboard near the CPU. L2 cache is now integrated into the CPU.
L3
L3
L3 cache is used on some high-end workstations and server CPUs.
Error Checking
Memory errors occur when the data is not stored correctly in the RAM chips. The computer uses different methods to detect and correct data errors in memory. Different types of error checking :
Error Checking
Memory errors occur when the data is not stored correctly in the RAM chips. The computer uses different methods to detect and correct data errors in memory. Different types of error checking :
L1 cache is internal cache and is integrated into the CPU.
Parity
L2 cache is external cache and was originally mounted on the motherboard near the CPU. L2 cache is now integrated into the CPU.
ECC
L3 cache is used on some high-end workstations and server CPUs.
Source : Cisco IT Essentials module