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Guide on How to safely Overclock your computer

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Old 03-02-2010
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Join Date: Jan 2010
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idea Guide on How to safely Overclock your computer
  

I saw many posts requesting help regarding overclocking their computer.

So i am posting a guide on Safe overclocking of your computer
This is a first guide of its kind on this site.

What is overclocking?

Overclocking, in simple terms, means increasing the speed of the processor (in this case) to perform more than its capable of, therefore increasing the load over it, hence the temperature.

For this, you'll need some tools. These are

1) CPU-Z It will tell you the core speed, multiplier, reference clock, HT link , core voltage etc....These terms may not have much meaning to you at the moment, but read on...

2) Real Temp This will show you the temperature of your processor, and all the cores in it. You can use another software Core temp for that, (just google it)

3) Stress Prime This is the most important software which allows the stressing of processor. It allows only 1 core to be stressed at a time, whereas another software called Orthos allows 2 or 4 cores to be stressed at a time. This includes small FFT, large FFT, and blend, for CPU stressing, memory stressing and both respectively.I recommend orthos for you to use.

These are the necessary software for overclocking, however, i recommend you download 3DMark (benchmarking software) to know the overclocked potential of your PC

Now, the last thing i need you to everything do is to know about your CPU and RAM. Especially what voltages they'r supposed to operate at.
Many high quality RAM sticks, like OCZ, Corsair can operate at 2.1 to 2.3V, which is a very big advantage. Some low quality RAM sticks like Dynet, Hynix are made to operate at 1.8V only, which resulting in being a bottleneck on the overclock. So find these values.

Basic Terminology

Whole overclocking process is done in the BIOS of your pc, so first of all, explore and familiarise yourselves with BIOS.

1) Reference clock-
Also called as CPU clock,this is responsible for most of the overclocking. The HT link speed, memory are all related to it. It usually starts from 200

2) HT multiplier-
This is responsible for the HT link of your pc, which determines the speed of transfer of input/output devices on motherboard.
It is multiplied by the reference clock to obtain HT link.
HT link, under default conditions is set to 1000MHz, as multiplier is 5x, and reference clock is 200.HT link above 1000 wont increase any performance

3) CPU Multiplier-
This is responsible for CPU speed, as this multiplied by the reference clock gives us the CPU speed. This is automatically set to 15 in many systems, 10 in some, it differs a lot. Many have fractional multipliers too, like 14.5

4) CPU voltage-
This is voltage running through the CPU. It is also called as vCore in many systems. This has to be increased in order to increase the CPU speed, but by very low values.

5) Memory Setting-
This determines the memory divider, hence affects the CPU speed.
Memory Speed(RAM) = CPU speed/ divider

This looks like Auto, DDR2 400, DDR2 533, DDR2 667, DDR2 800 etc
now some new motherboards support DDR3 RAM.

6) Memory Voltage-
The voltage running through the RAM stick. It can be increased to safe values for overclocking.

7) Memory timings-
These are usually represented as 5-5-5-15-21-1T

Lets see wat they actually denote

CAS latency ( CL ) ---- 5

RAS to CAS delay (tRCD) ---- 5

RAS Precharge (tRP) ---- 5

Cycle Time (tRAS) ---- 15

Bank Cycle Time (tRC) ---- 21

Command Rate (CR) ---- 1T

These are the timings for DDR2 667 RAM
They need to be changed, but mostly they change themselves if set on Auto
So they dont really have to be guided, and i recommend u set it on Auto.


Now that you have familiarized yourself with the BIOS, we come to the basic process of overclocking.
It is simple,

CPU speed= Reference Clock x CPU Multiplier

Just increase the CPU multiplier and reference clock,
,is it done?
No,its not done. There are many aspects remaining.

System stability depends on every factor mentioned here.
Lets just say, u increased the speed, ran orthos/prime stress test for 1 hour, and its stable
You increased the speed some more, and the orthos test failed within 10 minutes.
What are you going to do, decrease reference clock, HT link, change memory settings, what??

We will never know what may be the cause of glitch in our overclock, because we dont know the limits of any of the factors. So, first, we determine how far we can push each factor, and then combine the results.

How to overclock?


Motherboard

First we are going to find the limits of motherboard.
A motherboard limits are 1) HT link 2) reference clock

As explained above, the HT link is given by HT multiplier x reference clock
now, if the multiplier is 5, and reference clock is 200, it gives HT link as 1000Mhz, we increase reference clock to 225, HT link becomes 1125MHz
Some motherboards are able to handle this value, some give up even at 1060MHz. To find the limits of your motherboard, we will set every value at its lowest, and push reference clock to its highest.

Go to the BIOS, and set the following values, dont save them

Set Reference clock as 200 (or whatever is minimum for you)
Set CPU multiplier as 5x (or whatever is minimum for you)
Set HT multiplier as 5x (or whatever is maximum or you)
Set Memory setting as DDR2 400
Leave the voltages as it is.

Then, after you have set these values, increase the reference clock by 5Mhz, and reboot after saving the settings.

Run the orthos Blend test (make sure u run blend test) for 2 minutes. If no errors are found, increase the reference clock by 5Mhz more, and repeat the procedure.

If error occurs within 2 minutes of stress test, then reduce the HT multiplier to 4x. Save settings and reboot, and repeat the above procedure.

Let's assume you encountered another error at 4x multiplier, you reduced the multiplier to 3x, and then at the same reference clock you encountered the error while running blend stress test.
A situation will come when the error will occur irrespective of HT link.
That, my friend, is the limit of the reference clock for your motherboard.

You can try increasing the voltage of motherboard by .025V at a time and repeating the procedure, but it'll only result in negligible gain.
When you are done with this procedure, decrease the value of reference clock by 3-5MHz, to be on the safe side, and note that value.

We wont run a full test now because we will run a Blend test in the end.


CPU

Now, we are going to find the limits of CPU

Since we want to know what speed our CPU can really handle, we are going to increase the CPU speed.
CPU speed = Reference clock x CPU multiplier

The reference clock is already calculated before, but under Blend Stress test.. Now, to gain stability over increased reference clock, we need to increase the voltage by very small values,which allows us to increase reference clock even more,but note that a very small change in the value of voltage can cause a large change in temperatures.

So i recommend you buy any external cooling equipment, like a 5 inch fan, or or aftermarket water coolers.

By now, you should have found out the voltage at which your CPU runs, so that you can have a general idea how much increment is safe for your CPU


So, we set the multiplier to the maximum, and slowly increase the Reference clock. Set the following options in the BIOS,dont save them

Set Reference clock as 200 (or whatever is minimum for you)
Set CPU multiplier as 15x (or whatever is maximum for you)
Set HT multiplier as 5x (or whatever is maximum for you)
Set Memory setting as DDR2 400
Set the default voltages for CPU and memory.

Now increase the reference clock by 5MHz, save settings and reboot system.

Run orthos small FFT test for 2 minutes( mind you, small FFT test). If no errors are reported, increase reference clock by 5MHz and keep increasing till the test fails.

If the orthos test fails within 2 minutes, reduce the HT multiplier as before, and repeat the procedure from the starting, till the time when the error will occur again irrespective of HT link.

Once you are sure the maximum reference clock has been reached irrespective of HT link, increase the voltage by 0.0250V

Then increase the reference clock by 5MHz, and run orthos small FFT test.
If it pass the test, again increase the the reference clock, repeat till it fails orthos small FFT test for 2 minutes.

Again, increase the voltage by 0.0250V and find maximum reference clock at this voltage.

Increase the voltage again till it reaches a maximum value for your CPU, which you have already researched. Stop at the voltage you are comfortable with.

I strongly recommend not to increase the voltage above 1.45V without a good cooling equipment.

Now, a situation will come where your CPU cannot pass a 2 minutes orthos test, and you have increased the voltage to its maximum.

So, lower the reference clock by 3-5MHz, and run Orthos Small FFT test for 4 hours.
When i say 4 hours, i mean 4 hours. Actually, it is supposed to be 24 hours, but 4 hours will do.

If any error occurs, decrease the reference clock by another 3-5MHZ, and run the test again. Keep reducing ittill it passes the Orthos test for 4 hours.


RAM

Now, we find the limits of RAM

As i already said before, Memory speed = CPU speed/ divider

To have a high memory speed, we need a low divider,since the CPU speed has already been determined. We can now change the divider. But there is no option to set the divider in BIOS. You'll have to manipulate it using the above equation.

Now, divider can be manipulated by changing the CPU multiplier, and the memory setting.(DDR2 400, 533, 667, 800 etc)
Divider's lowest value is 5, it increases as the CPU multiplier increases.


So, in short, a low divider can be obtained by keeping a low CPU multiplier.

Now, keep the following settings, dont save them

Set Reference clock as 200 (or whatever is minimum for you)
Set CPU multiplier as 15x (or whatever is Maximum for you)
Set HT multiplier as 5x (or whatever is Maximum or you)
Set Memory setting as DDR2 667 (or 800 if u have DDR2 800, or 1066), timings being default.
Set the new CPU voltage which you set as maximum earlier
Set the voltage of the RAM to stock.

Now, increase the reference clock by 5MHz. Run orthos Large FFT test (notice Large FFT test) for 2 minutes. If it passes the test, increase the reference clock again, if it fails the test, reduce the HT multiplier to 4x,till the time comes when the error will occur again irrespective of HT link.

Once you are sure the maximum reference clock has been reached irrespective of HT link, increase the memory voltage (by .05V for low quality RAM sticks, or 0.1V for high quality sticks). I recommend not to increase it more, but you can increase it at your own risk.

After increasing the voltage,increase the reference clock by 5MHz, and run another Large stress test for 2 minutes. Keep increasing the reference clock till the test fails.

If the value for reference clock comes lower than expected or very low, try decreasing the voltage by 0.0125V, or whatever minimum value your motherboard can support.
Finally reduce the reference clock by3-5MHz,just to be on the safe side, and run orthos large FFT test for 4 hours. If it fails, lower the reference clock again, and run the test till stable clock has been achieved.


Producing results together

Now, since you know the maximum reference clock, HT link, CPU voltage, RAM voltage, you can set every factor to its highest value as calculated, and then finally run orthos Blend test again, for 4 hours. If it unstable, first check if the voltages are not too high, then continue with reducing the reference clock.

If another error comes, just fiddle with the settings, and determine what is cause of the problem.

Finally, run any benchmarking software like 3dMark06 or 3DMark vantage, and compare your scores before and after overclock.

Hope you found my Lengthy guide useful.
Any queries, feel free to ask. Any suggestions, feel free to make.

Note that this guide is to be used safely, and Techarena.in will not be responsible for any kind of damage done to your computer hardware.


Last edited by Raj : 03-02-2010 at 06:52 AM. Reason: Fine tuning
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  #2  
Old 03-02-2010
Member
 
Join Date: Sep 2005
Posts: 1,451
Re: Guide on How to safely Overclock your computer

Also, see some similar type of guides made on overclocking:

How to overclock your Graphic Card

Overclocking guide in charts

How to overclock ATI graphics card

Overclocking tutorial for newbies / beginners
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