In this way, DDR achieves greater bandwidth compared to SDR SDRAM it doubles the transfer rate without increasing the frequency of the clock. In the DDR SDRAM, the data is clocked at both edges – positive as well as negative edge – which results in doubling the data rate. The demand for higher data rates and larger data densities lead to the evolution of SDR into the DDR. The demand for higher data rates and larger data densities lead to the evolution of SDR into the DDR concept. What are the different types of DDR RAMs? The SDR SDRAM needs to wait for the completion of the previous command to be able to do another read/write operation. Single Data Rate signifies that SDR SDRAM can only read/write one time per clock cycle. For instance, the PC133 I/O, internal clock and bus clock are all 133MHz. Īs stated earlier, SDRAM stands for synchronous dynamic RAM where the I/O, internal clock and bus clock are synchronous. In general, cache memory reduces the average time to access data from the Main memory.

This memory stores the frequently used data/instructions and makes them immediately available to the processor whenever requested. The c ache acts as a buffer between external RAM and the processor. They reside internally in the processor or can be interfaced externally.

SRAM has been a default choice for cache memory as they are extremely fast and have very low access time. SDRAM is dynamic storage since the capacitors tend to discharge over time, and unless they are refreshed periodically SDRAM will not retain the stored data. As the size of a capacitor/transistor is smaller than that of a flip-flop, the memory density of SDRAM is higher compared to SRAM. The SDRAMs are slightly slower due to higher access time compared to SRAMs. The architectural difference between the two is that DRAM uses 1 transistor and 1 capacitor per memory bit, whereas SRAM uses 1 flip-flop (~ 6 transistors per flip-flop) to form one bit. SRAM is Static RAM and SDRAM is Synchronous Dynamic RAM. RAM is further categorized into SRAM and SDRAM. As the VLSI technology advanced, memory construction, memory chip density, size, speed, and communication interface have been improved to a great extent. ROM memory retains the data even after power is turned off. RAM is a volatile memory and data will be lost after the power is switched off. Primary memory is further categorized into Random Access Memory (RAM) and Read-Only Memory (ROM).

Ddr4 speed chart