The difference between DRR and DRR2

The standard DDR SDRAM is divided into DDR 200, DDR 266, DDR 433 and DDR 400. Its standard operating frequencies are 100MHz, 133MHz, 166MHz and 200MHz respectively, and the corresponding memory transfer bandwidths are 1.6 GB/ s and 2. 12GB/ s respectively. Novices are often confused by DDR 266, PC 2 100 and other words. It should be explained here that DDR 266 and PC 2 100 are actually the same thing, but their expressions are different. DDR 266 refers to the working frequency of the memory (the actual working frequency is 133MHz, which is equivalent to 266MHz SDRAM), while PC 2 100 refers to its memory transmission bandwidth (2 100 MB/ s). Similarly, PC 1600 is DDR 200, PC 2700 is DDR 333, and PC 3200 is DDR 400.

DDR2 can be regarded as an upgrade and extension of DDR technical standards: the core frequency of DDR is equal to the clock frequency, but the data frequency is twice as high as the clock frequency, which means that data must be transmitted twice in a clock cycle. While DDR2 adopts the "4-bit prefetch" mechanism, the core frequency is only half of the clock frequency, and the clock frequency is half of the data frequency, so that even if the core frequency is 200MHz, the data frequency of DDR2 memory can reach 800mhz-the so-called DDR2 800.

At present, the existing standard DDR2 memory is divided into DDR2 400 and DDR2 533, and there will be DDR2 667 and DDR2 800 in the future, with core frequencies of 100MHz, 133MHz, 166MHz and 200MHz respectively. Its bus frequency (clock frequency) is 200MHz, 266MHz, 333MHz and 400MHz respectively, its equivalent data transmission frequency is 400MHz, 533MHz, 667MHz and 800MHz respectively, and its corresponding memory transmission bandwidth is 3.2 GB/ s, 4.3 GB/ s, 5.3 GB/ s and 6.4 GB/ s respectively.