An explanation of DDR versus DDR2

Article Technical Level: Intermediate

RAM: Vendors randomly decide to list their ram speeds based on a “PCXXXX” standard or a MHz standard, they convert based on a formula related to data transfer rates. PC2100 = 266 MHz, PC3200 = 400 MHz, PC4200 = 533 MHz, PC5300 = 667 MHz, PC6400 = 800 MHz. There is of course more divisions inbetween, before, and after but these are the big ones. Something that needs to be considered though is there is also DDR(1) and DDR2. The original DDR has “latency” (time for data to get from one point to another) significantly lower then DDR2. This is sort of like how cache differences work. DDR2 was designed with higher latencies (bad) but higher bandwidth as well (good). DDR(1) generally ends at PC3200 (highest official bandwidth of DDR) and DDR2 generally starts at PC4200. The PC4200 / 533 MHz, again, refers to bandwidth. This is how many megabytes (MB) per second are possible to transfer across the memory bus. Again though, DDR2 has significantly higher latencies so it takes longer for that larger amount of data to get where it’s going. The industry can’t seem to decide on a standard but over the last few years it has migrated to DDR2 due to lower costs. DDR2 also uses less energy as compared to DDR due to higher efficiencies, a smaller manufacturing process and less power intensive design. Very extreme performance nuts still tend to prefer DDR(1) due to its significantly lower latencies.