All you wanted to know about overclocking and raid

Overclocking

now lets discuss memory overclocking

Introduction

A lot has been said about CPU and VGA overclocking, but it is also possible to overclock your RAM memory in order to boost your PC performance without spending a penny. Memory overclocking is done thru the motherboard's setup (you can enter the setup program by hiting the Del key during the memory counting that appears everytime you turn your PC on), almost always on the same menu where the CPU clock takes place (usually called "Frequency/Voltage Control" or similar).
The process is a little bit boring, like all overclocking procedures. You will have to change the memory clock, save the new configuration, reboot your PC and check if your computer is still working correctly. We recommend that you run your favorite 3D game for a while in order to check if everything is running alright. We also recommend that you run a benchmarking software in order to check the perfomance gain from the overclocking. As we will explain later, sometimes memory overclocking decreases the PC performance depending on the configurated timings (we will cover this topic on this tutorial as well). We recommend that your run two programs, Sandra, on its Memory Bandwidth Benchmark module to check the increase on memory performance (download it at #-Link-Snipped-#), and SuperPI, to check the increase on the overall PC performance (download it at #-Link-Snipped-#).
After rebooting the PC and testing if the overclocking was successful, you have two options. If the overclocking went right, you can go back to the motherboard's setup and try increasing the memory clock even more and repeating the whole process, until you find the maximum overclocking capability of your memory module. If the overclocking went wrong, you should go back to the setup and lower the memory clock, since the clock you configured isn't making the memory work right.
All overclocking procedures can work or not. It is not possible for us to tell you if it will work in your system and the maximum clock memory you will achieve on it. Overclocking is a trial-and-error process.
That's the basic idea. There are two tricks in order to achieve a higher overclocking level: raising the memory voltage and playing with the memory timings. We will now explain in details how the memory overclocking is done, including those two tricks.
Overclocking your Memory

There are two modes of configuring the memory clock: synchronous, were the memory clock is tied to the CPU external clock, and asynchronous, where the memory clock can be configured independently from the CPU clock. The mode your computer has depends on its motherboard.
The synchronous mode is usually found in entry-level motherboards while asynchronous mode is usually found in high-end motherboards. Also, notice that many low-end motherboards don't have any overclocking configuration at all.
So, how do you know what mode your motherboard uses? Enter setup, go to the "Frequency/Voltage Control" menu and pay attention on the available options. If you find any option to change the memory clock ("Memory Clock" or "Memory Frequency", sometimes under a sub-menu called "DRAM Configuration" or "Memory Configuration"), your memory is running at asynchronous mode. Otherwise it is running at synchronous. Also pay attention that in order to change clock configurations you may need to change the option that allows you to do so. This option can have several different names, like "Clock Control", "System Performance" or "DDR Timing Setting by". Sometimes memory configuration options are under "Advanced Chipset Setup" and not under "Voltage/Frequency Control", so you need to also take a look on this menu and look for memory configuration options there.

Let's explain in detail how do you overclock your memory.

Synchronous Mode

The main disavantage of the synchronous mode is that in order to overclock your memory, you will need to overclock your CPU. Usually that's ok since maybe you are trying to overclock both memory and CPU. But in many cases the maximum external clock your CPU is reaching is limited by the memory or vice-versa.
For example, by trial-and-error basis you found out that the maximum external CPU clock you can configure on your system is 180 MHz. So, your memory is also working at 180 MHz ("360 MHz" since DDR memories are rated with two times its real clock) or more, depending on the host/memory ratio settings that some synchronous motherboards have. For example, on the motherboard of Figure 4 the memory can be set to run with the external CPU clock multiplied by 2 or by 2.5. This motherboard was targeted to Pentium 4 CPU, so when the external clock was set to 133 MHz ("533 MHz"), the memory clock could be configured at 266 MHz or 333 MHz. Of course setting it to 333 MHz would make more sense if you use DDR333 or DDR400 memories. But when we overclocked the CPU external clock to 180 MHz, at the 2.5 ratio shown the memory would run at 450 MHz.

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So, on motherboards with synchronous mode, when you find out the maximum CPU external clock you cannot know for sure what is limiting you to increase the CPU external clock. Can be a CPU limitation or can be a memory limitation. On motherboards with the host/memory ratio configuration shown on Figure 4 you can change the ratio to check which component is limiting the overclock. For example, we would lower the ratio from 2.5 to 2 in order to make the memory tun at 360 MHz instead of 450 MHz and then try again to increase the CPU external clock. If you really cannot increase it over the 180 MHz limit (in our example), it means that the CPU is the component limiting the clock increase. On the other hand, if after lowering the ratio you now can increase the CPU external clock a little more, it was the memory that was limiting the overclock. Then you can see the new maximum external CPU clock you can achieve with this new configuration.
When the CPU is limiting the clock increase, your have to face a terrible truth: your memory could achieve a higher clock rate, but you cannot configure it to use this higher clock rate because your motherboard doesnâ€™t have a configuration to do so. That's one disavantage of using cheap motherboards and that's why overclockers perfer high-end motherboards.
So, this problem doesn't affect motherboards with asyncrhonous memory configuration. Since you have two different configuration sets for CPU and memory, the maximum clock the CPU can reach is not limited by the memory, and also the maximum clock the memory can reach is not limited by the CPU, which is far better for overclocking.

Asynchronous Mode

As we explained, some motherboards allow you to increase the memory clock separately from the CPU external clock, which is the best option for achieving a high overclocking.
There are two ways of configuring the memory clock on asynchronous motherboards: using predetermined fixed value or typing in the clock you want. This option will depend on the motherboard model.
The motherboard we shown on Figure 3 the memory clock options are fixed. As you can see, you can only choose the memory clock from a predetermined list of settings. This is not the best case but it is better than not having any memory overclocking option at all.
The best scenario is to have a motherboard where you can type in the memory clock you want, like you can see on Figure 5. Usually you need to change a configurarion called "DDR Timing Setting", "Clock Control", "System Performance" or similar from "Auto" to "Manual" in order to change the memory clock.

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As we mentioned before, you will need to increase the memory clock, save the configuration, reboot your PC and test if the memory overclocking worked or not. If it worked, you need to repeat the process again trying a higher clock. If not, you need to repeat the process again trying a lower clock. You will need to repeat the whole process several times until you find out the maximum clock rate your memory accepts.

Raising the Memory Voltage

The most common trick in overclocking is increasing the voltage of the component (CPU, video card or memory). Increasing the voltage usually allows the component to reach a higher clock.
So, after you find out the maximum clock your memory can reach, you can try increasing its voltage to see you if you can achieve a higher clock. But you need to pay attention to not burn your memory! DDR memories use a standard voltage of 2.5 V and we do not recommend that you go over 2.8 V (there are memories from OCZ where the manufacturer states that you can run them up to 3.2 V without burning them).
The memory voltage settings can also be found under the "Frequency/Voltage Control" menu on setup under names as "DIMM OverVoltage Control", "DRAM Voltage Regulator" and "DIMM Voltage Regulator". Low-end motherboards don't have this kind of configuration.
The options you will find depends on the motherboard model. Some motherboards have more voltage options than others and the way the voltage increase is expressed also depends on the motherboard model.
The motherboard featured on Figure 6 has only three options for memory voltage: Normal (which is 2.5 V), + 0.1 V (i.e. 2.6 V) and + 0.2 V (i.e. 2.7 V).

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On the motherboard shown of Figures 7 and 8 you will need first to change the "Voltage Fine Tuning" option in order to change the memory voltage. On this motherboard you have four options for memory voltage: Normal (which is 2.5 V), + 0.1 V (i.e. 2.6 V), + 0.2 V (i.e. 2.7 V) and + 0.3 V (i.e. 2.8 V).

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One more example of Figure 9, where you can change the memory voltage to 2.7 V, 2.8 V and 2.9 V.

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Changing the Memory Timings

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). #-Link-Snipped-#. 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
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.

All you wanted to know about overclocking and raid

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