What Is RAM Latency? Is It Important?

In normal, latency is a delay. So, the time period RAM latency means the delay a reminiscence module takes to reply to a CPU request. 

The very first thing you take a look at when shopping for a reminiscence module might be the capability and reminiscence frequency. But, one facet most newbie and even intermediate PC fans overlook when getting RAM is its latency. 

Ideally, you’ll wish to select a RAM with decrease latency. But there are just a few elements that have to be considered, as latency doesn’t completely enhance a RAM’s efficiency.

So, let’s dive additional into the subject,

Understanding RAM Latency

RAM latency is mainly the delay it takes for the CPU to obtain and course of the information from RAM as soon as the reminiscence controller has requested it. 

Two elements specifically have an effect on RAM latency, RAM frequency and CL or CAS Latency. Both these values are talked about in your reminiscence sticks. 

Note: CAS Latency and RAM Latency are utterly completely different.

In your reminiscence module, you will have seen writing akin to 8GB DDR4 3600 CL 18. DDR4 is the Double Data Rate Generation. 3600 is the switch price, which is 3600 MegaTransfers per second. 

And lastly, CL is the CAS Latency or Column Address Strobe Latency and is measured in a clock cycle. In the above instance, the CAS latency of the reminiscence module is 18 clock cycles.

Here is the system to calculate whole RAM latency in seconds.

(CL*2000)/switch price

Here is a desk representing how CAS latency impacts reminiscence latency.

This clearly makes the reminiscence module with decrease CAS Latency the winner, provided that the RAM velocity is similar. 

If you’re uncertain about selecting between two reminiscence modules, we advocate getting a RAM with increased frequency and decrease CL.

You may also use the system talked about above to calculate the RAM latency to search out out the precise delay in nanoseconds. And select one with the decrease latency.

Memory Timings

Besides the DDR model, RAM’s switch velocity, and CL, you may also have seen a sequence of numbers on the reminiscence sticks, which seems one thing like 20-19-19-40. 

Data on a RAM is saved on rows and columns. These quantity represents the variety of clock cycle to entry information from mentioned rows and columns.

Memory timings characterize the next.

tCL-tRCD-tRP-tRAS

• tCL: This is the CAS Latency of your reminiscence stick. This is the full clock cycle required to fetch the information as soon as it has been requested by the CPU, or reminiscence controller in particular.
• tRCD: This is Row deal with to Column Address Delay. This is the variety of clock cycle required to open a row and entry the required column to entry information within the reminiscence.
• tRP: This is Row Precharge Time. This means the full clock cycle wanted to entry a separate row with a particular column.
• rRAS: This is Row Active Time. This is the minimal clock cycle a row wants to remain open to entry the information. 

If you wish to overclock your RAM, you may decrease these values within the BIOS. This permits the RAM to entry information rather more rapidly, reducing the latency. However, in doing so, additionally, you will must amp up the voltage.

Higher Transfer Rates or Lower CAS Latency

Ideally, you’ll wish to go for a RAM that has a decrease total RAM latency using the system from above. But that doesn’t imply going for a DDR4 2133 CL 13 RAM as an alternative of a DDR4 3200 CL 20 as each of them have comparable total latency.

Although each of those reminiscence modules have the identical RAM latency, it’s all the time a good suggestion to go for reminiscence with increased switch charges moderately than CAS latency. This is as a result of the velocity at which RAM and the CPU talk straight impacts how briskly the applying and the OS reply, and makes the system carry out higher.

In conclusion, when selecting RAM for a selected capability, the primary precedence needs to be the frequency or the switch charges. And in that frequency vary, selecting a module with decrease CAS latency could be higher. 

Mixing RAM With Different Memory Timings

Another question most customers have is, whether or not it’s attainable to combine completely different reminiscence sticks with variable timings. Yes, it’s completely attainable so that you can do that. If you’re operating two reminiscence sticks on twin channels, each the reminiscence will run on a decrease of the 2 frequencies.

In case of reminiscence timings, the system will use the reminiscence timing that has the upper clock cycles.

However, there are a number of instances the place mixing reminiscence with completely different frequency, reminiscence timings, and even capability brought about random system crash and frequent blue display of dying (BSOD) error. 

Here, even by myself laptop computer, I confronted the identical problem some time back when mixing two completely different reminiscence modules. I used an 8 GB DDR4 2600 CL 19-16-16-34 and an 8 GB DDR4 3200 CL 20-15-15-39.

The system had a most RAM frequency of 2400. So, each reminiscence have been operating at 2400. And the RAM with decrease latency, i.e., 8GB DDR4 2600 ran on reminiscence timings 20-15-15-39.

This brought about the system to ceaselessly show a BSOD error. To repair this, I used a reminiscence module much like the second RAM, i.e., 8GB DDR4 3200 CL 20-15-15-39.

The system was an outdated HP laptop computer, in order that might be why it didn’t help reminiscence with completely different reminiscence timings. However, I additionally tried mixing reminiscence with my office setup (newer motherboard and CPU) and didn’t run into any BSOD error. 

So, mixing reminiscence with completely different timings might or might not work, relying in your system. But my suggestion could be to make use of similar reminiscence to save lots of your self from any issues sooner or later.