RAM Latency

[Arwanell]

what is it?

[TacticalCuda]

how long the ram takes to respond to a task from the CPU.

[Justin_]

How long it takes for the CPU to access what is stored in RAM

[Mug]

 

Latency is a time interval between the stimulation and response, or, from a more general point of view, as a time delay between the cause and the effect of some physical change in the system being observed.

 

So basically how fast your ram is to get something for the processor.

This is notably different from the speed of the ram which is proportional to the data rate (unit storage per second).

[Godlygamer23]

how long the ram takes to respond to a task from the CPU.

Not just that. There is latency within the memory itself.

http://www.hardwaresecrets.com/understanding-ram-timings/

[Arwanell]

how long the ram takes to respond to a task from the CPU.

 

 

How long it takes for the CPU to access what is stored in RAM

 

 

So basically how fast your ram is to get something for the processor.

This is notably different from the speed of the ram which is proportional to the data rate (unit storage per second).

so less = better?

[zyntaxable]

so less = better?

Yep

[SteveGrabowski0]

Latency is the period of time in between when a command is issued and when it is started. Think of downloading something on the internet. All the data comes from Europe, so you click the download button and first it takes time to send that command all the way to Europe, eg, a propagation delay. Then the server with the data starts transmitting onto its link once it gets your download command. The propagation delay here is your latency.

 

Note latency is a time, not a number of clock cycles, so a CAS latency number is meaningless in and of itself. Saying CAS 11 or CAS 15 RAM is slow is like saying my 3 GHz cpu is fast. If that CPU is a Pentium 4, no, it's a slow piece of shit. If that CPU is a Xeon E5, then it's a fucking monster at 3 GHz. So just like you need to know the architecture along with the clockspeed to evaluate a CPU's speed, you need not only the CAS number, but the clockspeed of the RAM to say whether a RAM kit has high or low latency. CAS latency refers to the number of cycles of latency it takes to do the column address strobe, which is one part of finding where in RAM to read/write. But the actual latency associated with the column address strobe is

 

LATENCY = CAS_NUMBER / CLOCKSPEED.

 

The CAS number is in units of cycles while the clockspeed is in units of cycles/second. So that gives latency in units of seconds.

Edited January 2, 2016 by Godlygamer23

[Daniel123dk]

what is it?

Say this: 1600mhz cas 10 is as fast as 1333mhz cas 9. In the other hand, 1600mhz cas 9 is as fast as 1866mhz cas 10 :-)

[Arwanell]

Say this: 1600mhz cas 10 is as fast as 1333mhz cas 9. In the other hand, 1600mhz cas 9 is as fast as 1866mhz cas 10 :-)

i was looking at these two:

1866 cas 11

1600 cas 10

[alexc026]

what is it?

RAM latency refers to delays in transmitting data between the CPU and RAM. If you're looking to buy ram the higher the speed the higher the latency usually that is why high speed ram with low latency is so expensive

Also much higher cas latency negates fast ram eg. 2133mhz ram with cas latency 20 because the amount of latency is reducing the performance benefit of the high clocked ram

[SteveGrabowski0]

i was looking at these two:

1866 cas 11

1600 cas 10

 

In this example 1866 kit has both lower latency and faster burst throughput.

[Daniel123dk]

i was looking at these two:

1866 cas 11

1600 cas 10

They are most likely the same :-) the 1866 just looks better on paper.

[Nena Trinity]

You want that number as low as possible!