I read somewhere that to find the real latency of the ram you can use the following rule :
1/((RAMspeed/2)/1000) x CL = True Latency in nanoseconds
ie for DDR1 with 400Mhz clock speed, is it logical to me to divide by 2 to get the FSB speed or the real bus speed which is 200Mhz in this case. So the rule above seems to be correct for the DDR1.
From the other side, DDR2 also doubles the freq of the bus in relation to the previous DDR1 generation (ie 4 bits per clock cycle) according the article "What Every Programmer Should Know About Memory".
So, in the case of a DDR2 with a 800Mhz clock speed, to find the "True Latency" the above rule should be accordingly changed to
1/((RAMspeed/4)/1000) x CL = True Latency in nanoseconds
Is that correct? Because in all the cases I read that the correct way is to take RAMspeed/2 no matter if it's DDR, DDR2, DDR3 or DDR4.
Which is the correct way to get the true latency?
Ok I found the answer.
Everytime the manufacturers increased the memory clock speed they did it in a constant rate which always was the double (2x) of the FSB clock speed. ie
MEM CLK FSB
-------------------
DDR200 100 MHz
DDR266 133 MHz
DDR333 166 MHz
DDR400 200 MHz
DDR2-400 200 MHz
DDR2-533 266 MHz
DDR2-667 333 MHz
DDR2-800 400 MHz
DDR2-1066 533 MHz
DDR3-800 400 MHz
DDR3-1066 533 MHz
DDR3-1333 666 MHz
DDR3-1600 800 MHz
So, the memory module has always the double speed of the FSB.