difference between ddram and sdram?

Answer 1

DDR SDRAM or double-data-rate synchronous dynamic random access memory is a class of memory integrated circuit used in computers. It achieves greater bandwidth than the preceding single-data-rate SDRAM by transferring data on the rising and falling edges of the clock signal (double pumped). Effectively, it nearly doubles the transfer rate without increasing the frequency of the front side bus. Thus a 100 MHz DDR system has an effective clock rate of 200 MHz when compared to equivalent SDR SDRAM, the “SDR” being a retrospective designation.

With data being transferred 64 bits at a time DDR RAM gives a transfer rate of [mbcr x 2 x 64] / 8; annotated it looks like this: (memory bus clock rate) × 2 (for dual rate) × 64 (number of bits transferred) / 8 (number of bits/byte). Thus with a bus frequency of 100 MHz, DDR-SDRAM gives a max transfer rate of 1600 MB/s.

JEDEC has set standards for speeds of DDR SDRAM, divided into two parts: The first specification is for memory chips and the second is for memory modules.

As DDR is superseded by the newer DDR2, the older version is often now referred to as DDR1

Answer 2

SD RAM and DDR RAM are type of memory integrated circuit used in computers. SDRAM stand for Synchronous Dynamic Random Access Memory and basically consists of collection of cells, IO buffers and power circuitry. All three subsystems are synchronized at the time of working. DDR RAM stands for Double Data Rate Random Access Memory.

The major difference between SD RAM and DDR RAM is speed. DDR RAM can pass the data at approximately double the speed of SD RAM and the simple formula of performance is “more fast data transfer, better will be the performance”. This double speed of DDR RAM is due to its property of transferring data on both the rising and falling edges of the clock signal.

Answer 3

SDRAM stands for synchronous dynamic random access memory. In tech speak, that means it it waits for a clock signal before responding to its control inputs.

DDR SDRAM stands for double-data-rate synchronous dynamic random access memory. In tech speak, this means it achieves greater bandwidth than SDRAM by transferring data on the rising and falling edges of the clock signal.

Basically, DDR is faster -- twice as quick -- than SD.

Answer 4

Dynamic random access memory (DRAM) is a type of random access memory that stores each bit of data in a separate capacitor within an integrated circuit. Since real capacitors leak charge, the information eventually fades unless the capacitor charge is refreshed periodically. Because of this refresh requirement, it is a dynamic memory as opposed to SRAM and other static memory. Its advantage over SRAM is its structural simplicity: only one transistor and a capacitor are required per bit, compared to six transistors in SRAM. This allows DRAM to reach very high density. Since DRAM loses its data when the power supply is removed, it is in the class of volatile memory devices.

SDRAM means synchronous dynamic random access memory which is a type of solid state computer memory.

Other dynamic random access memories (DRAM) have an asynchronous interface which means that it reacts as quickly as possible to changes in control inputs. SDRAM has a synchronous interface, meaning that it waits for a clock signal before responding to its control inputs. It is synchronized with the computer's system bus, and thus with the processor. The clock is used to drive an internal finite state machine that pipelines incoming instructions. This allows the chip to have a more complex pattern of operation than DRAM which does not have synchronizing control circuits.

Pipelining means that the chip can accept a new instruction before it has finished processing the previous one. In a pipelined write, the write command can be immediately followed by another instruction without waiting for the data to be written to the memory array. In a pipelined read, the requested data appears a fixed number of clock pulses after the read instruction. This delay is called the latency and is an important parameter to be considered when purchasing SDRAM for your computer. It is not necessary to wait for the data to appear before sending the next instruction.

SDRAM chips are rated according to their maximum clock rate and their read cycle time. Clock rate is directly proportional to maximum bandwidth and is affected primarily by the speed of the internal state machine and interface circuitry. Read cycle time affects the delay between issuing a command and initiating the corresponding operation and is determined primarily by the speed of the memory cells themselves.

SDRAM modules are typically rated according to their maximum clock rate (which may differ from that of the chips on the module) and by their CAS latency. CAS latency is the delay between specifying a column address and receiving the first data output and is closely related to read cycle time. It is specified in clock cycles, typically with the assumption that the module is running at its maximum speed. However, CAS latency is actually programmable by the memory controller, and a lower CAS latency setting may be viable if the module is running slower than its rated clock speed. When 100 MHz SDRAM chips first appeared, some manufacturers sold modules that could not reliably operate at that speed. In response, Intel published the PC100 standard, which outlines requirements and guidelines for producing a memory module that can operate reliably at 100 MHz. This standard was widely influential; the term "PC100" quickly became a common identifier for 100 MHz SDRAM modules, and modules are now commonly designated with "PC"-prefixed numbers (although the actual meaning of the numbers varies widely among different types of modules).

Answer 5

the difference between ddr and sd is the speed difference basically for the same bus speed it's twice as fast sd bus speed went up to 133Mhz the equivalent in ddr is 266Mhz

Answer 6

DDRam is double layer, SDRam is single layer...

the two are incompatible stick with one kind...i think DDR is better

Answer 7

ddr is newer than sdram.