tRAS, tRCD, tRP, tRC ?

[W1zzard]

CAS Latency
The CAS latency is the delay, in clock cycles, between sending a READ command and the moment the first pice of data is available on the outputs.


tWR - Write Recovery Time:
tWR is the number of clock cycles taken between writing data and issuing the precharge command. tWR is necessary to guarantee that all data in the write buffer can be safely written to the memory core.


tRAS - Row Active Time:
tRAS is the number of clock cycles taken between a bank active command and issuing the precharge command.


tRC - Row Cycle Time:
The minimum time interval between successive ACTIVE commands to the same bank is defined by tRC.
tRC = tRAS + tRP


tRCD - Row Address to Column Address Delay:
tRCD is the number of clock cycles taken between the issuing of the active command and the read/write command. In this time the internal row signal settles enough for the charge sensor to amplify it.


tRP - Row Precharge Time:
tRP is the number of clock cycles taken between the issuing of the precharge command and the active command. In this time the sense amps charge and the bank is activated.


tRRD - Row Active to Row Active Delay:
The minimum time interval between successive ACTIVE commands to the different banks is defined by tRRD.


tCCD - Column Address to Column Address Delay


tRD - Active to Read Delay ?:


tWTR - Internal Write to Read Command Delay:
tWTR is the delay that has to be inserted after sending the last data from a write operation to the memory and issuing a read command.


tRDA - Read Delay Adjust


Memory timings are given as: CAS-tRCD-tRP

Or in short:
Lower value=better performance=less stability
EXCEPT for TRAS which is a pain in the 4$$ because only it varies between RAMs, some RAM perform best @ 11, while some perform best @ a rediculusly low value like 5.

Take a look at this: http://www.corsairmemory.com/memory_basics/153707/