I have some ? about Memory Latency

From the Memory FAQ : ( http://www.tomshardware.com/forum/55024-30-memory-pleas... )

Q: How does memory access work, and what do the timings stand for?
A:
MEMORY ACCESS:
1. tRCD (RAS to CAS Delay) 2-3 cycles, The row is selected by the Memory Controller.
2. CAS (Column Address Strobe) 2,2.5,3 cycles (DDR), The Memory Controller selects the column and now the ROW is
ACTIVE, and the READ COMMAND is sent.
3. Data is sent to the DQ pins after CAS delay.
4. tRAS (Row address Strobe) 6 cycles, The module waits a certain period of time for the data to be active.
5. tRP (RAS precharge) 2 cycles, The Memory Controller DEACTIVATES the row.
6. Memory Cycle repeats as requested by the Memory Controller.

The timings are represented as follows:
2-3-2-6 1T (CAS, tRCD, tRP, tRAS)

The 1T is the command rate (see key term: command rate)

Q: How do I adjust the latency timings of my memory modules?
A: Some motherboards allow the latency settings to be adjusted in the system's BIOS. To enter the system BIOS you will need to press either the 'delete' or 'tab' key before your system starts. However, many Dell, HP, and Compaq systems do not allow for changes to the latency timings.

Q: What is the difference between 1T and 2T memory timings?
A: A 2T command rate means that commands are presented to DRAMs for two consecutive clocks, as opposed to one consecutive clock for a system with a 1T memory setting.


ALso Trc is the (row cycle time) which is the total time it takes to cycle the process (ie. 5+5+5+15 =30 in your case )