DDR3 SDRAM

DDR3 SDRAM

In electronic engineering, DDR3 SDRAM or double-data-rate three synchronous dynamic random access memory is a random access memory interface technology used for high bandwidth storage of the working data of a computer or other digital electronic devices. DDR3 is part of the SDRAM family of technologies and is one of the many DRAM (dynamic random access memory) implementations.

DDR3 SDRAM is an improvement over its predecessor, DDR2 SDRAM, and the two are not compatible. The primary benefit of DDR3 is the ability to transfer at twice the data rate of DDR2 (I/O at 8× the data rate of the memory cells it contains), thus enabling higher bus rates and higher peak rates than earlier memory technologies. There is no corresponding reduction in latency, as that is a feature of the DRAM array and not the interface. In addition, the DDR3 standard allows for chip capacities of 512 megabits to 8 gigabits, effectively enabling a maximum memory module size of 16 gigabytes.

With data being transferred 64 bits at a time per memory module, DDR3 SDRAM gives a transfer rate of (memory clock rate) × 4 (for bus clock multiplier) × 2 (for data rate) × 64 (number of bits transferred) / 8 (number of bits/byte). Thus with a memory clock frequency of 100 MHz, DDR3 SDRAM gives a maximum transfer rate of 6400 MB/s.

DDR3 SDRAM

DDR2 SDRAM

DDR2 SDRAM

DDR2 SDRAM is a double data rate synchronous dynamic random access memory interface. It supersedes the original DDR SDRAM specification and the two are not compatible. In addition to double pumping the data bus as in DDR SDRAM, (transferring data on the rising and falling edges of the bus clock signal), DDR2 employs an I/O buffer between the memory and the data bus so that the data bus can be run at twice the speed of the memory clock. The two factors combine to achieve a total of 4 data transfers per memory clock cycle.

With data being transferred 64 bits at a time, DDR2 SDRAM gives a transfer rate of (memory clock rate) × 2 (for bus clock multiplier) × 2 (for dual rate) × 64 (number of bits transferred) / 8 (number of bits/byte). Thus with a memory clock frequency of 100 MHz, DDR2 SDRAM gives a maximum transfer rate of 3200 MB/s.

DDR2-SD RAM

Dual Inline Memory Module (DIMM)

DIMM (Dual Inline Memory Module)

DDR SDRAM chips :

 Standard DIMMs have 168 pins, one notch on either side, and two notches along the contact area.

DDR DIMMs

on the other hand, have 184 pins, two notches on each side, and only one notch along the contact area.

All DIMMs are either 64-bits (non-parity) or 72-bits (parity or error correcting code [ECC]) wide (data paths).

Dual Inline Memory Module (DIMM)

 A typical 168-pin SDRAM DIMM. The one shown here is 72-bit, although the dimensions would be the same for 64-bit

The pins are numbered from left to right and are connected through to both sides of the module on the SIMMs. The pins on the DIMM are different on each side, but on a SIMM, each side is the same as the other and the connections carry through.

Double Data Rate Dual Inline Memory Module (DDR-DIMM)

A typical 184-pin DDR DIMM. The one shown here is 72-bit, although the dimensions would be the same for 64-bit.

RDRAM

RDRAM

RDRAM is a wide-channel device. They transfer data only 16 bits (2 bytes) at a time (plus 2 optional parity bits), but at much faster speeds. RIMM typically runs at 800MHz, so the overall throughput is 800 × 2, or 1.6GB per second for a single channel—the same as PC1600 DDR SDRAM. Dual-channel PC800 RDRAM is also currently the fastest type of PC memory, followed by PC2100 DDR SDRAM. Whether your board supports (requires) dual-channel RDRAM is dictated by the motherboard chipset; currently, the Intel 840 and 850 chipsets support dual-channel RDRAM.

A Typical RD RAM (RDRAM)

DDR SDRAM

DDR SDRAM

Double data rate (DDR) SDRAM memory is an evolutionary design of standard SDRAM in which data is transferred twice as quickly. Instead of doubling the actual clock rate, DDR memory achieves the doubling in performance by transferring twice per transfer cycle: once at the leading (falling) edge and once at the trailing (rising) edge of the cycle. DDR SDRAM uses a new DIMM module design with 184 pins. DDR DIMMs are rated for either PC1600 (200MHz x 8) or PC2100 (266MHz x 8) operation or normally run on 2.5 volts. They are basically an extension of the PC100 and PC133 DIMMs redesigned to support double clocking, where data is sent on each clock transition (twice per cycle) rather than once per cycle as with standard SDRAM.

A typical DDR SD RAM

SDRAM

SDRAM

 Synchronous DRAM (SDRAM) is for Synchronous DRAM, a type of DRAM that runs in synchronization with the memory bus. SDRAM delivers information in very high-speed bursts using a high-speed, clocked interface

RAM: Random Access Memory

RAM: Random Access Memory

RAM (random access memory) is what is most often referred to when PC memory is discussed. RAM is the form of volatile memory used to hold temporary instructions and data for manipulation while the system is running.

Nonvolatile and Volatile Memory

Nonvolatile and Volatile Memory

There are two major classes of computer memory: Nonvolatile and Volatile. Nonvolatile Memory is retained even if the power is shut off. The setup data held in CMOS, discussed in the preceding lessons, is a good example of nonvolatile memory. If the data is lost when the computer loses power, the memory is said to be Volatile.

Read Only Memory (ROM)

Read Only Memory (ROM):-

ROM stands for Read only Memory. It consists of those instructions that prepare the computer for use. ROM instructions are automatically loaded into the Main Memory. These instructions cab only be read but cannot be changed or deleted. It is not possible to write new instructions into the ROM. It stores data and instructions permanently. When we switch off the computer, the instructions stored in the ROM are not lost. Therefore it is called a non-volatile memory. 

Primary Storage or Main Memory (RAM)

Primary Storage or Main Memory (RAM) :-

Primary storage, presently known as main memory or simply RAM (Random Access Memory), is the only one directly accessible to the CPU. The CPU continuously reads instructions stored there and executes them as required. Any data actively operated on is also stored there in uniform manner.

Memory stores three basic categories of data.

1. Operating system and other system software that control or maintain the computer and its devices
2. Application programs that carry out a specific task such as word processing etc.
3. Data to be processed by the application programs and resulting information.

 RAM varies in size like 128 MB, 256 MB, 512 MB to 4 GB.  RAM can not store data and instruction permanently. When we switch off the computer, all data and instructions from RAM are washed or vanished. Therefore it is called volatile memory.