Choosing RAM can be daunting, because this decision may have a tangible impact on your user experience. How many browser tabs can you keep open, how many layers can you have sầu open in Photosiêu thị, và how fast will your game load? All of this is directly affected by your choice of RAM.

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How does RAM work?

Let us use a busy highway as an analogy. The number of RAM sticks is kind of lượt thích the number of lanes on the road: the more sticks of RAM you have sầu, the more lanes you have sầu open, & the more cars the road can hold at a given time.

The kích thước of your RAM, in this analogy, would be how many cars each lane can hold. And the tốc độ of your RAM is like the tốc độ limit sign posted on the highway.

Therefore, a stick of 8GB RAM with a cloông chồng speed of 2666mhz can process 8GB of data at a given time, and 2666mhz is the tốc độ at which the information will be processed.

This is why adding more RAM will not necessarily make your computer faster: you’re adding more lanes lớn the road and more oto capathành phố, rather than increasing the speed limit. Adding more RAM may be useful for users in certain RAM-hungry situations (heavily tabbed Chrome users, 3D rendering/modeling program users, and recent console—e.g. PS3, Wii U—emulation users), but more RAM is almost never the answer as to lớn why a computer is not running a game at your desired performance level.

How bởi you determine RAM latency?

The first column represents CAS latency, also known as “Column Access Strobe.” This is the number of clock cycles that pass between when an instruction is given & when the information is made available. If you tell someone to lớn “duck!”, CAS latency would be the delay between when you comm& them to lớn duchồng and when the other person reacts.

But CAS does not exist in a vacuum, và must be put inlớn a formula alongside other specifications in order to determine the true latency of your RAM.

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To calculate the true latency of your RAM in nanoseconds, use the following formula:

(CAS latency/RAM clock speed) x 2000 = latency in nanoseconds

If you have a CAS of 15 & a cloông xã tốc độ of 2400mhz, this would be your true latency:

(15/2400) x 2000 = 12.5 nanoseconds

If you have sầu a CAS of 17 and a clock speed of 2666mhz, this would be your true latency:

(17/2666) x 2000 = 12.75 nanoseconds

Thus, higher CAS timings can result in a higher latency even with higher clochồng speeds. However, that doesn’t explain what happens in a situation where the true latency of two sticks of RAM are tied, despite them having different cloông chồng speeds (because the faster-clocked choice has a worse latency). In situations where that kind of tie occurs, the higher speed of RAM takes precedence over which has superior CAS latency. Thus, when comparing a stick of DDR4-3000 RAM with a CAS of 15 and a stiông chồng of DDR4-3600 RAM with a CAS of 18 (which would both have a true latency of 10 nanoseconds), the DDR4-3600 should be preferred.

Similarly, the comparison of CAS latency between RAM options of identical clochồng speeds is where CAS matters most. A stiông xã of DDR4-3600 RAM with a CAS of 15 has a true latency of 8.33 nanoseconds, while a same-size/same-speed stiông xã with a CAS of 19 has a latency of 10.56 nanoseconds. In this case, the DDR4-3600 RAM with a CAS of 15 is objectively better than the DDR4-3600 RAM with a CAS of 19.


How vì chưng you choose RAM?

Motherboards and CPUs are rated for the maximum amount and tốc độ of RAM they can handle. If your motherboard and CPU is only rated up to lớn 3600mhz, then you should only purchase or overclochồng RAM up to lớn 3600mhz. However, a quiông chồng perusal will reveal that there’s over a hundred variants of 3600mhz RAM available. If you narrow it down khổng lồ the form size of the RAM, perhaps lớn 16gb (2 x 8GB), you still have sầu a few dozen options. This is where CAS (and cost) comes in.

For 16GB RAM at 3600mhz, you’ll find options ranging from a CAS latency of 15 khổng lồ 19. You’ll also find the price has a range of nearly $100 USD difference, & that this difference closely correlates khổng lồ CAS latency. For example, the G.Skill Ripjaws V DDR4-3600 with a CAS of 19 costs about $130 USD. By comparison, the G.Skill TridentZ DDR4-3600 with a CAS of 15 is roughly $230 USD. The lower the CAS, the faster the RAM—và consequently, the more expensive.

When deciding between RAM of different cloông xã speeds, the RAM with the higher cloông xã tốc độ is superior; but when choosing between RAM of identical clock speeds, the RAM with lower CAS latency is faster. This is where the constraints of your budget must vì chưng battle with your desire for speed (as well as any aesthetic considerations such as RGB lighting).

When dealing in nanoseconds, the difference may not seem significant—and it can certainly be argued that, for the average user, the difference between a CAS of 15 và a CAS of 19 is not worth breaking the ngân hàng. But when choosing between RAM options within budget, you should choose the lowest CAS at a given speed for the best performance.