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DDR SDRAM is a SDRAM that allows for data transfers on both edges of the clock cycle, effectively doubling its speed. Although DDRAM is in desktop computers, its increased power efficiency makes it an ideal solution for laptops. It comes in different shapes and sizes, depending on the type of computer.

DDR2 SDRAM(Double Data Rate Two SDRAM):
Its primary benefit is the ability to operate the external data bus twice as fast as DDR SDRAM. This is achieved by improved bus signal. The prefetch buffer of DDR2 is 4 bit(double of DDR SDRAM). DDR2 memory is at the same internal clock speed (133~200MHz) as DDR,  but the transfer rate of DDR2 can reach 533~800 MT/s with the improved I/O bus signal. DDR2 533 and DDR2 800 memory types are on the market.

DDR3 SDRAM(Double Data Rate Three SDRAM):
DDR3 memory reduces 40% power consumption compared to current DDR2 modules, allowing for lower operating currents and voltages (1.5 V, compared to DDR2's 1.8 V or DDR's 2.5 V). The transfer rate of DDR3 is 800~1600 MT/s. DDR3's prefetch buffer width is 8 bit, whereas DDR2's is 4 bit, and DDR's is 2 bit. DDR3 also adds two functions, such as ASR (Automatic Self-Refresh) and SRT (Self-Refresh Temperature). They can make the memory control the refresh rate according to the temperature variation.

DDR4 SDRAM (Double Data Rate Fourth SDRAM):
DDR4 SDRAM provides the lower operating voltage (1.2V) and higher transfer rate. The transfer rate of DDR4 is 2133~3200 MT/s. DDR4 adds four new Bank Groups technology. Each bank group has the feature of singlehanded operation. DDR4 can process 4 data within a clock cycle, so DDR4's efficiency is better than DDR3 obviously. DDR4 also adds some functions, such as DBI (Data Bus Inversion), CRC (Cyclic Redundancy Check) and CA parity. They can enhance DDR4 memory's signal integrity, and improve the stability of data transmission/access.

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A capacitor is a passive two-terminal electrical component that stores potential energy in an electric field. The effect of a capacitor is known as capacitance. While some capacitance exists between any two electrical conductors in proximity in a circuit, a capacitor is a component designed to add capacitance to a circuit. The capacitor was originally known as a condenser.

Its function is to store the electrical energy and give this energy again to the circuit when necessary. In other words, it charges and discharges the electric charge stored in it. Besides this, the functions of a capacitor are as follows:

1. It blocks the flow of DC and permits the flow of AC.

2. It is used for coupling of the two sections.

3. It bypasses (grounds) the unwanted frequencies.

4. It feeds the desired signal to any section.

5. It is used for phase shifting.

6. It is also used for creating a delay in time.

7. It is also used for filtration,especially in removing ripples from rectified waveform.

8. It is used to get tuned frequency.

9. It is used as a motor starter.

10. It is also used in conjunction with a resistor to filter ripples in a rectifier circuit.

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Clock Cycle is the amount of time between two pulses of an oscillator. 

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Clock Cycle is the amount of time between two pulses of an oscillator. 

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There are two types of Random Access Memory or RAM, each has its own advantages and disadvantages compared to the other. SRAM (Static RAM) and DRAM (Dynamic RAM) holds data but in a different ways. DRAM requires the data to be refreshed periodically in order to retain the data. SRAM does not need to be refreshed as the transistors inside would continue to hold the data as long as the power supply is not cut off.

The additional circuitry and timing needed to introduce the refresh creates some complications that makes DRAM memory slower and less desirable than SRAM. One complication is the much higher power used by DRAM memory, this difference is very significant in battery powered devices. SRAM modules are also much simpler compared to DRAM, which makes it easier for most people to create an interface to access the memory.

Structurally, SRAM needs a lot more transistors in order to store a certain amount of memory. A DRAM module only needs a transistor and a capacitor for every bit of data where SRAM needs 6 transistors. Because the number of transistors in a memory module determine its capacity, a DRAM module can have almost 6 times more capacity with a similar transistor count to an SRAM module. This ultimately boils down to price, which is what most buyers are really concerned with.

1. SRAM is static while DRAM is dynamic
2. SRAM is faster compared to DRAM
3. SRAM consumes less power than DRAM
4. SRAM uses more transistors per bit of memory compared to DRAM
5. SRAM is more expensive than DRAM
6. Cheaper DRAM is used in main memory while SRAM is commonly used in cache memory

DRAM

Dynamic random-access memory (DRAM) is a type of storage that is  dynamic so it needs to be refreshed or given a new electronic charge every few milliseconds to compensate for charge leaks from the capacitor.

SRAM

SRAM (static RAM) is random access memory (RAM) that retains data bits in its memory as long as power is being supplied. Unlike dynamic RAM (DRAM), which stores bits in cells consisting of a capacitor and a transistor, SRAM does not have to be periodically refreshed.

SDRAM

Synchronous dynamic random access memory (SDRAM) is dynamic random access memory (DRAM) that is synchronized with the system bus. It is a generic name for various kinds of dynamic random access memory (DRAM) that are synchronized with the clock speed that the microprocessor is optimized for.Short for Synchronous DRAM, a type of DRAM that can run at much higher clock speeds than conventional memory.

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Dual In-line Memory Module, DIMM is a module containing a circuit board and one more random access memory chips. DIMMs have a 168-pin connector and, since the advent of the Pentium Processor, a 64-bit path. Because of the new bit path, DIMMs can be installed one at a time, unlike SIMMs that would require installation in pairs.
Advantages

1. DIMMs have separate contacts on each side of the board, which provides twice as much data as a single SIMM.

2. The command address and control signals are buffered on the DIMMs. With heavy memory requirements, this buffering reduces the loading effort of the memory.

Short for Single In-line Memory Module, SIMM is a memory module developed by Wang laboratories in 1983. The SIMM circuit board that holds six to nine memory chips per board, the ninth chip usually an error checking chip (parity or non parity). The SIMM was used with computers using a 486, early Intel Pentium, and compatible processors. However, because the Pentium is 64-bit and a SIMM is only 32-bits wide, they must be installed two at a time when used with any 64-bit processor.

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Clock Speed - is the speed of a computer processor, or CPU.

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Clock Speed - is the speed of a computer processor, or CPU.

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Generally speaking, the higher number of pulses per second, the faster the computer processor will be able to process information. The clock speed is measured in Hz, typically either megahertz (MHz) or gigahertz (GHz). For example, a 4GHz processor performs 4,000,000,000 clock cycles per second.

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PC2-5300 | DDR2-667 | 333 МГц | 5300 | 10600
PC2-6400 | DDR2-800 | 400 МГц | 6400 | 12800
PC2-8500 | DDR2-1066 | 533 МГц | 8500 | 17000
PC3-6400 | DDR3-800 | 400 МГц | 6400 | 12800
PC3-8500 | DDR3-1066 | 533 МГц | 8500 | 17000
PC3-10667 | DDR3-1333 | 667 МГц | 10600 | 21200
PC3-12800 | DDR3-1600 | 800 МГц | 12800 | 25600
Memory bandwidth is the rate at which data can be read from or stored into a semiconductor memory by a processor. Memory bandwidth is usually expressed in units of bytes/second, though this can vary for systems with natural data sizes that are not a multiple of the commonly used 8-bit bytes.