RAM CL-?

[Cybopache]

Ok I got a question !

What does it mean with  the numbers  e.g :low latencies of 4-4-4-12.?

and what is the difference between 4-4-4-12 and eg.3-4-3-9. Does it have with speed to do?

and witch one of them  are so the fastest?

cybo

[erjin999]

Those are, I believe, latency times, how long a memory controller should wait before trying to access RAM in various ways, like precharge latency times and stuff. Better explanations will come from cyborg and them lot, and I expect to hear from veK as well, being a computer enthusiast.

[Cyborg]

What Re-erjin999 says is correct.

The latencies are displayed in nanoseconds, and mean how long the memory controller should wait for each operation. I'm not sure if you want to know what each latency does, but it's the first of the latency numbers that's displayed as the CAS latency, or CL ( usually 2, 2.5 or 3 on DDR sticks and 3, 4 and 5 on DDR2 ).

[Cybopache]

ok thx for help, I did some recearch my self and found a little about it. Enough to understand anyway.

cybo

[veK]

everything said...

and yes: the lower the number the better (faster) it is

[erjin999]

Of course, lower latency is better, but why do newer rams have high latencies ?

Is it because they transfer data twice as often as when I first read up on the issue (DDR) ?

Any ideas about the reason/s ?

[veK]

the key difference between DDR and DDR2 is that in DDR2 the bus is clocked at twice the speed of the memory cells, allowing transfers from two different cells to occur in the same memory cell cycle.

the DDR2 bus frequency is boosted by electrical interface improvements, on-die termination, prefetch buffers and off-chip drivers. as a trade-off the latency is increased. because of this higher latency, DDR running at the same bus speed as DDR2 is generally considered superior - however, DDR2 is able to run at substantially higher bus speeds

the first DDR2 modules were very slow, but meanwhile they have advanced and latencies aren't as slow as they used to be when DDR2 was new.