Another trick for memory overclocking is to change the memory timings (a.k.a. "latency"). By raising the memory timings, you will be able to achieve a higher clock rate with your memory. But there is a catch: the memory can run slower.

The memory delays a certain amount of time to deliver the data requested by the CPU. This time is called CAS Latency or simply CL and is expressed in the number of clock cycles the memory will delay return back the requested data. For example, a memory configured with a CL of 2 will delay two clock ticks to deliver the data, while a memory configured with a CL of 3 will delay three clock ticks to deliver the same data. So, a memory with a CL of 2 will be faster than a memory with a CL of 3.

If you raise the memory's CL, you will be able to increase its clock, but sometimes the memory can run slower, even though it is running at a higher clock rate. There are times when it is better to run your memory with a lower CL and a lower clock rate than it is to run it with a higher clock and a higher CL. If you decide to raise the memory timings to achieve a higher clock rate, you should measure the memory performance before and after, then compare the numbers to see which option gives you better performance.

We are talking about CL, but there are, in fact, five timing types: CL, tRCD, tRP, tRAS and CMD. These timings are expressed in numbers such as 2-2-2-5 and 3-4-4-8 (The CMD parameter is optional.) We've written a tutorial explaining what each one of these numbers mean. Please refer to it to learn more about this subject. The idea is simple: by lowering those numbers, you will achieve higher performance. B raising them, you will achieve a higher overclocking, but it can lead to lower performance (As we said, you will need to measure the performance before and after changing timings, and clock to see what is the best option.)

On some motherboards, you can change each parameter individually, while others, you have some fixed predetermined options from a list configuring all timings on a single option (e.g., "2-2-2-5," "3-4-4-8," etc.) Some very high end motherboards will have many more timing options. (See Figure 11.)

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Figure 10: Memory timing options

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Figure 11: Exemple of a motherboard with far more timing options

We suggest you change only one option at a time. If you change more than that, you won't know which option is preventing your overclocking from working in case your overclocking fails.

If your motherboard has the CMD timing option (which is optional), configure it as "T1," since at "T2" the memory performance is lower.