Memory Timings Examined
Timings are usually listed something like 2-2-2-6-1 or 1-6-2-2-2. What the numbers stand for are CAS-tRC-tRP-tRAS-CMD
1. tRAS Active Precharge Delay, this is the delay between a command being received (from the memory controller) and firing up the RAS.
2. tRP [o]RAS Precharge[/i]. Memory is stored in a gridlike array and at the end of every row (memory is searched cell by cell), there is a delay associated with "moving to the next row".
3. tRCD RAS to CAS Delay: memory is stored in a gridlike array and this latency represents the time that must pass between locating the row and then starting to look for the column.
4. CAS. Column Acces Strobe, this number represents the number of cycles that must pass before the memory can locate the exact hex addresss of the memory cell required.
5. CMD Command Rate is the delay time associated with locating which bank of memory to search through (this explains why having say, four DIMMs usually results in CMD-2T: a lot more virtual memory locations need to be searched through to translate to a physical location for further searching)
