RAM has different type, speed and latency:
- TYPE is mostly how many times data is read (or written) during 1 clock cycle; DDR transfers data 2 times per clock cycle, DDR2 does it 4 times, DDR3 8 times.
- there are special types for servers and workstations, that have built-in error correction; these are ECC types, and have different "RANKS" that you have to be aware of! Normally single rank and dual rank can be used on the same motherboard and in the same memory channel, but since dual rank has more chips and thus normally higher capacitive load they have to mounted in the slots farthest away from the CPU.
- there are also even more special types for servers, called "ECC REGISTERED". Those types have an extra buffer between the channel bus and the memory chips, which makes it possible to use a high amount of RAM blocks. They will only work in hi-end machines like the epic HP-Z800, and cannot be mixed with non-registered types.
- SPEED is number of bits or Bytes (1 Byte is 8 bits) per second.
- LATENCY is how much time there has to be between subsequent read/write cycles.
|changing laptop RAM|