Cas Latency or Timing Definition

The simplest way to think of cas latency (or timings) is by associating it with how much delay your ram will have. Timings represent the gap between the processor sending information to the RAM and the RAM responding to it. High cas latencies will result in slower RAM.

You can expect that as memory becomes faster it will naturally have higher timings. For example, memory with a speed of 1066 Mhz will likely have a cas latency of 5-5-5-15. Whereas, memory with a speed of 2133 Mhz will possibly have a cas latency of 9-11-10-28. Aim to find RAM with a high speed first. Then focus on finding one with the lowest cas latency.

What is RAM?

RAM is an abbreviation for "random access memory". It is also referred to as "memory". RAM is where everything goes to when it is loaded. You probably noticed how long it takes for everything to start up at first. That is because the hard drive has all of this information. The hard drive is a huge pool of information that can be saved even when the computer is turned off. The problem with the hard drive is that it's slow. To deal with this slowness, the information needs to be loaded into the RAM. RAM holds a much smaller amount of space than hard drives but is many, many times faster. Once the information is loaded to RAM, everything will run smooth. RAM, however, cannot save information after the computer is turned off. This is why the computer will need to go through the start up process again after you turn it on.

When most people hear about RAM, they think about how much space it has. This is usually measured in gigabytes. Common amounts of space are anywhere from 2 GB's to 16 GB's. A good amount now days is around 2 to 8 GB's. If you have any less, you'll bottleneck your computer so it won't run well. There is little point to having more than 8 GB's because you probably won't use it anytime soon. You can buy multiple sticks of RAM depending on how many slots you have in your motherboard. Your motherboard will have limitations on what it can hold. It is important to find this out first.

Another important thing to look out for too is the speed of RAM. Most people don't think to check for this but the whole point of having RAM is that it's fast! A common type of memory is DDR or double data rate. This is currently generation of this is DDR3. The newer generations run at faster speeds. RAM speeds are measured in megahertz or MHz. Some standard speeds may be anywhere for 1066 MHz to 2000 MHz. Both the RAM and the motherboard have to support the same maximum speed. Otherwise, the speed of the RAM will run at the lowest common supported speed. An example of this is provided below.

Another thing to check is the RAM's cas latency. Latency is how many clock pulses there are between the RAM sending the information and the computer being able to use it. It is important to have as few clock pulses go by as possible. Unfortunately, the higher the frequency, the higher the latency will probably be. This is simply something you accept as you purchase faster RAM. Just remember to search for RAM with the highest frequency first and after you've identified the frequency you want find the lowest cas latency as possible.

This example came from Newegg.com. Generally when searching for RAM, I like to sort the results by rating. This puts the most popular RAM toward the top. In this particular example, there are to sticks totaling 8 GB's of space. 2 x 4GB tells us that there are two sticks and each stick has 4 GB's. The next part tells us what kind of RAM it is. 240 pins is the standard for desktop computers. DDR3 is the newest kind of RAM. 1333 is the amount of megahertz the RAM runs at. This is a very important number to know. You want as many MHz as you can get. Cas Latency and Timing tells you how much delay the RAM has. Keep this number as low as possible. It also states that it is a dual channel kit. Try to also find a motherboard that is dual channel. These are the factors to look at when choosing RAM.