Lesson 02 - Cooling, Stress Testing and Benchmarking
Before we start overclocking the CPU we need to see where the CPU is in regards to its cooling and performance. We're going to run a few programs in Windows. The first is called RealTemp. You can find it at www.techpowerup.com/realtemp. It runs in Windows XP, Vista and 7. Just extract the files into a folder using your favorite unzipping tool and run RealTemp.exe. This program tells us the temperature that each of the CPU cores is running at in degrees Celsius as well as how many degrees the cores are away from the CPU's maximum allowed temperature.
It keeps track of the minimum and maximum temps and the time they occurred. It also lists the CPU type, its MHz, the base clock and multiplier and the load on the CPU. When idling in Windows the load will be low because no CPU intensive programs are running. The temperature at idle is around 45C. For a Core i5 or Core i7 in this case 45 C is high for an idling CPU and it's a sign of poor cooling.
This computer has been running for a little over a year and I know when it was first powered on the idle temp was in the mid 30C which was good. Either the cooler has come slightly off the CPU, probably from being moved around a lot, or the thermal compound has started to deteriorate. Only being a year old, deterioration of the compound isn't likely so the cooler is probably very slightly ajar. This is still well within a safe temperature, for a Core i5 or i7, anything below 90C is safe and the CPU can run at that temp for years.
You'll notice that at idle the multiplier and therefore the speed keeps changing. This is a power saving feature that is turned on by default in the BIOS. This is a good thing. Your CPU doesn't need to be full on all the time, especially if it's just sitting there doing nothing. When the CPU load increases it switches to a high multiplier and if the CPU is taxed constantly the multiplier is raised to its maximum.
While we are doing our overclocking tests, trying to get the CPU to run as fast as it can, we are going to disable these power saving features in the BIOS. This will make sure the stress tests we put the CPU through are very thorough. We want to put the CPU through the worst possible circumstances to make sure the overclock is stable. Having the power saving features on would give the CPU a break and that's not what we want. After we reach our maximum stable overclock we will turn the power saving features back on to save electricity and extend the CPU's life.
We have the idle temperature of the CPU, now we need to find the full load temp. To fully utilize the CPU we are going to use a program called Prime95. You can find Prime95 on several sites for free and download the 32bit or 64bit version, depending on if you're running a 32 or 64 bit OS. Extract the zip file to a folder and run Prime95.exe.
It will default to the Run a Torture Test dialog. To stress the CPU cores to their maximum and get them as hot as possible, we want to use the In-place large FFTs option. On a Core i7 CPU it will open 8 windows. The Core i7 has 4 cores, but can run two threads or processes per core. This is called Hyperthreading by Intel. This makes the CPU look like an 8 core CPU to the OS and programs. Core i5 CPUs don't have Hyperthreading so Prime95 will open 4 windows. Keep in mind that this is a worst case scenario for the CPU. It is highly unlikely that all 4 cores will be kept this busy by any other program or game.
Prime 95 has been running for about 5 minutes. If we look at RealTemp we see the cores are up to around 85C. This is another sign the cooler isn't performing well. The temps shouldn't be going higher than 80C. I'm going to shut the system down and re-attach the cooler with some fresh thermal compound and see what that does to the temperatures.
Re-attaching the Stock Intel Cooler
I've removed the case cover and laid the case on its side. This 8 pin power cable is in the way so I'll disconnect it along with CPU fan cable. Before removing a stock Intel CPU cooler you need to unlock all four of its' push pins by rotating them counter clockwise, using a flat head screwdriver, so the arrow points toward the cooler. Then pull up on each to release them. The cooler can now be removed by pulling straight up, although this often requires a fair amount of force.
I'll use a paper towel to remove the majority of the thermal compound from the CPU. Then a cotton swab dipped in 90% or higher isopropyl alcohol to remove the rest of the compound. I'll do the same to remove the compound from the cooler.
Before I re-attach the cooler I have to set the push pins back to the locked position be rotating them clock wise using a flat head screwdriver. I'll turn the cooler over so I can apply some new thermal compound. On this round-base cooler I will put a small amount right in the center. When you attach the cooler to the CPU, the compound will evenly spread out to cover the base.
Now I'll lower the cooler onto the CPU making sure the white pins are aligned with the holes in the motherboard. Then I'll push on the top of the cooler to get each of the pins through the holes. When re-attaching the cooler this takes quiet a bit more force to accomplish compared to the first time you attached the cooler. Once the cooler is flush with the motherboard and CPU you need to push down on two of the pins, at opposite corners and then the other two opposite corners to secure the cooler to the motherboard.
Next I'll re-attach the 8 pin power cable to the motherboard and the CPU cooler's fan cable.
The cooler is re-attached so I'll put the case cover back on and get back into Windows.
To get a gauge on how well our CPU is performing with the stock settings we need to run a CPU benchmark. We're running Windows XP here so we will download 3dMark06. If you're running Windows Vista or 7 you can download 3dMark Vantage. Vantage does not work in Windows XP. Both of these benchmarks will push the CPU to its' limits and give us a benchmark we can use to compare the performance with the current stock settings to the performance after we overclock the CPU. Each time we reach a stable overclock we can run this benchmark to show the performance improvement. This isn't necessary in overclocking the CPU, but it is interesting and satisfying to see the improvements. Once it downloads just run the exe and install it. We've already installed 3dMark06 so I'll fire it up.
Before we run the benchmark it's important to close down as many other running programs as possible. Even your browser can take up 10 to 15% of the CPU's time and this can effect the benchmark score. What ever you do just try and make sure the programs running are consistent between now and the next time you benchmark, after you overclock, to give as true a comparison as possible.
The free versions of 3dMark06 and Vantage don't allow you to select only the CPU tests so I'll run the standard benchmark. This tests the video card as well.
The tests take about 10 minutes to complete and in 3dMark06 this CPU score with stock settings is 5420.
In the next lesson we will go into the BIOS, go over all the overclocking related settings and where they can be found in different motherboard makers BIOSs. Then we will do a basic overclock, taking this Core i7 920 CPU running at stock 2.66GHz to 3.5GHz.