Types

• RAM comes in many types, each with different specifications. For example, a common type of computer memory is Double Data Rate 2 (DDR2) RAM, which is twice as fast as regular DDR RAM. Similarly, DDR3 is considered to be about twice as fast as DDR2.
  
  

Numbering

• Memory names typically include a number, such as "PC3-6400" or "PC3-10600." PC and the number 3 denote that this is DDR3 memory; the number 2 represents DDR2 and no number represents DDR. The second set of numbers represents the RAM's peak data transfer rate in megabytes per second (MB/s), which essentially is the speed. Using the examples, PC3-6400 RAM has a peak data transfer rate of 6400 MB/s and PC3-10600's peak transfer rate is 10600 MB/s, making the latter the faster type.
  
  

Expert Insight

• To compare quality and speed among the same type of RAM from different manufacturers, look for expert reviews. Such reviews typically offer detailed information regarding the RAM specifications and speed.