Another trick for memory overclocking is to change the memory timings (a.k.a. "latency"). 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 to give 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.

So, 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. Sometimes is better to run your memory with a lower CL and a lower clock rate than to run it with a higher clock and a higher CL. If you decide on raise the memory timings to achieve a higher clock rate, you should measure the memory performance before and after and compare the numbers to see wich option gives you a 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 like 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: lowering those numbers, the higher the performance you will achieve. Raising them you will achieve a higher overclocking, but it can lead to a 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).

In some motherboards you can change each parameter individually. On some 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'd suggest you to change only one option at a time. If you change more than one option at the same time, you won't know which option is preventing your overclocking from working in the case your overclocking fails.

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