Lesson 08 - Combining the Overclocks of the CPU, CPU NB, HT Link and RAM into a Complete System Overclock
Introduction
In this lesson we are going to combine the overclocks of the CPU, CPU Northbridge, HT Link and memory into a complete system overclock. We'll first show how to do this with a Black Edition CPU and then with a non Black Edition CPU.
There is no sample video for this lesson. This video jumps right in overclocking the CPU and we just can't give that away can we.
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Complete System Overclock with a Black Edition CPU
I'll hit F12 and load the default profile we made in Lesson 3. This sets all of the frequencies, multipliers and voltages to the stock settings. We'll start with the CPU because the CPU overclock will give the greatest performance increase. I'll check my notes and the CPU was stable at 3755MHz with a CPU voltage of 1.4V. It was also stable using a CPU voltage of 1.45V at 3848MHz. To get to 3848MHz we set the CPU multiplier to 18.5 and the reference clock to 208MHz. I also need to set the CPU voltage to 1.45V since that amount of CPU voltage was required to make the overclock stable.
Next I'll set the CPU Northbridge. According to my notes it's maximum stable speed was 2440MHz with a CPU NB voltage of 1.175V. I'll increase the CPU Northbridge multiplier and we have a problem. With the reference clock set to 208MHz and a CPU NB multiplier of 12 the CPU Northbridge goes up to 2496MHz. This is higher than it's maximum stable speed. One option would be to lower the multiplier to 11. However this computer has 1600MHz rated RAM which has an actual speed of 800MHz. You want the CPU Northbridge speed to be at least 3 times the speed of the RAM for the best performance. 800 times 3 is 2400MHz. What we can do is go back to the CPU which is current set to run at 3848MHz and raise the CPU multiplier to 19 and lower the reference clock to 202MHz. This lowers the CPU frequency by 10MHz which is fine. We won't notice the difference. Now if we change the CPU Northbridge multiplier to 12 the frequency goes to 2424MHz and is only 16MHz below it's maximum. I also need to set the CPU NB voltage to 1.175V which is required to make the overclock of CPU Northbridge the stable. Next I'll go down and set to the HT Link multiplier to 12 which takes it's frequency to 2424MHz as well.
The memory frequency is at 1616MHz which is only a very slight overclock. On this system with 1600MHz RAM we are going to not overclock the RAM any more and instead lower it's CAS timing settings to increase performance. Before we do that its a good idea to test the combination of overclocks we've got going here. I'll hit F10 to save and exit and go into Windows. I'll run Prime95 on the blend setting for at least 20 minutes and the CPU test in BurnInTest. It passed. If it didn't pass I would set the CPU Northbridge and HT Link multipliers back to 10 and run the stress tests in Windows. Then overclock the CPU Northbridge and HT Link and stress test them separately.
The stress tests passed though so I'll leave them at 12 and go into the DRAM configuration. I'll look at my notes and I know the system was stable with the CAS timings set to 8 8 8 21 and 1T with the RAM voltage at 1.5V. We tested this with the memory frequency at 1600MHz so its possible this 16MHz increase will cause these CAS timings to not be stable. I'll hit F10 and stress test again. It passed. If it didn't pass I would come back into the BIOS and set the CPU, CPU Northbridge and HT Link so they are at or below their stock speeds. Then I would go back to the DRAM configuration, set the timings back to their stock settings and start the testing over. Lowering each setting and stress testing in Windows until I found the lowest stable timings at 1616MHz.
The times of 8 8 8 21 and 1T are stable at 1616MHz on my system. Lets go into Windows and run the Performance Test on the CPU. We ran this test back in Lesson 2 with the system at it's stock speeds. I'll run the xxxxxx test and the xxxx xxxx as xxxxx. That's a xx% increase in performance. I'll go back into the BIOS, hit F11 and save this configuration. I'll call it 3838 2424 1616 which is the speed of the CPU, CPU NB, HT Link and Memory.
Complete System Overclock with a non-Black Edition CPU
Now lets see how to combine the overclocks with a non Black Edition CPU. I'll hit F12 and load the default profile that has the frequencies, multiplier and voltages set to their stock values. We'll start with the CPU because the CPU overclock will give the greatest performance increase. I'll check my notes and the CPU was stable at 3848MHz with a CPU voltage of 1.45V. This is a non Black Edition CPU so we can't increase the CPU multiplier. To find the reference clock frequency we need to get to 3848MHz I'll divide 3848 by the CPU multiplier of 16 and I get 240.5. I'll set the reference clock to 240 and that gives a CPU frequency of 3840MHz. I also need to set the CPU voltage to 1.45V since that amount of CPU voltage was required to make the overclock stable.
Changing the reference clock frequency also changed the frequency of the CPU Northbridge, HT Link and memory. The CPU Northbridge and HT Link are at 2400MHz. According to my notes it's maximum stable speed was 2440MHz with a CPU NB voltage of 1.175V. I'll set the CPU NB voltage to 1.175V. According to my notes the HT Link is fine at 2400MHz. The RAM is at 1920MHz which is far above what my RAM is capable of. I'll lower it's multiplier from 8 to 6.66 and it changes to 1600MHz which is what my RAM is rated for. I want to decrease the CAS timings to get more performance from the RAM. I'll look at my notes and I know the system was stable with the CAS timings set to 8 8 8 21 and 1T with the RAM voltage at 1.5V.
I'll press F10 to save and exit and go back into Windows. I'll run Prime95 on the blend setting and the CPU test in BurnInTest to make sure the system is stable. It is.
What if we instead had 1333MHz rated RAM that we wanted to overclock and let's say we already determined in Lesson 7 that the RAM can run at up to 1450MHz at 1.5V. With the reference clock set to 240MHz the memory multipliers only give us the option of 1333MHz or 1600MHz RAM speeds. How do we get the RAM to run at 1450MHz? We have to change the reference clock frequency. I can find the reference clock frequency we need by dividing 1450 by the RAM multiplier of 5.55 and I get 261.26. So if I change the reference clock to 261MHz the RAM frequency changes to 1449. This new reference clock speed also changes the frequency of the CPU, CPU Northbridge and HT Link way above their maximum stable speeds. On this non Black edition CPU I can't raise the multipliers but I can lower them. I'll lower the CPU multiplier to 14.5 which changes the frequency to 3785. This is 63MHz slower than the CPU is capable of. We probably won't ever see this difference in the real world.
Next I need to lower the CPU Northbridge and HT Link frequency so they are lower than 2440MHz which is the maximum speed they were stable at when we tested them. I'll press F10 to save and exit and go back into Windows. I'll run Prime95 on the blend setting for at least 20 minutes and the CPU test in BurnInTest to make sure the system is stable. It is.
So we have overclocked our CPU, CPU Northbridge, HT Link and RAM to be as fast as they are capable of and still stable.
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