Intel Core 2 Overclocking Basics
Author: Frank Stroupe
Editor: Shawn Knight
Date: 09-08-2008

Test Rig:

Intel Core 2 Quad Q6600 B0 stepping
Gigabyte EP45-DQ6 motherboard
Crucial Ballistix Red Tracer DDR2-800 4GB Kit
Sapphire Radeon HD 4850 Toxic
Silverstone Decathlon DA-800 PSU

Monitoring Software:

There are some things you will need before you start. While overclocking, you will need to monitor your CPU temperature, and your CPU and Memory speeds. I recommend that you get CPUZ for CPU and memory speed monitoring, and CoreTemp for temperature monitoring. Both are well-proven stable third-party programs that show measurements with as much accuracy as the hardware's sensors. Also, both are compatible with Vista.

Most motherboards come with some kind of utility to monitor CPU speed and CPU temperature. Some of these are totally standalone, such as Asus' PC Probe II. Other brands have begun incorporating temp monitoring into their overclocking software, such as Gigabyte's EasyTune6. If your motherboard does the latter, I do not recommend using it, as I previously mentioned, these programs often introduce instability into the system. I highly recommend uninstalling any overclocking software prior to overclocking via the BIOS.

Hardware Requirements:

Without going into a lot of detail, before overclocking you really should invest in an aftermarket CPU cooler; 99% of stock coolers just don't cut it. The higher operating speeds and higher voltages will really heat up your CPU, and a better cooler will help keep it cool. I also recommend an adequately ventilated case, with minimum of two 120mm case fans. An adequate power supply is also important. Overclocking requires steady, clean power, and a PSU struggling to keep up won't provide that. High performance memory also helps, though most motherboards allow a lot of flexibility with memory dividers to keep your memory speed low while cranking up the CPU. I have had the memory I am using overclocked to DDR2-1200, so I'm not going to worry about that. Some boards allow the CPU to be overclocked totally independent of the memory, as this board does.

Something I find invaluable for overclocking is a motherboard speaker. I know that many people don't connect them nowadays, and not all cases have one included. Besides being able to hear if the rig started correctly, you can sometimes determine the reason for a failed overclock by the beep code. For example, a long unending beep usually means the rig wouldn't start due to memory instability.

BIOS Differences:

Again, be aware that all BIOS are not equal. Every BIOS is tailored specifically for the individual motherboard, and two BIOS for motherboards from the same company may look totally different. Better BIOS will tell you your CPU and memory speed as you increase the FSB, but be aware that not all give you the CPU speed. In that case, you will need to figure out your CPU speed on your own. The number you manipulate to change the FSB will be called different things on different BIOS. On the board I am using, it is called “CPU Host Frequency”. Other boards call it “FSB Frequency”.

Some boards show the actual FSB, which on a newer CPU will be 800, 1066, 1333, or 1600mHz. Other boards show a 3-digit number, this number is .25 of the actual front side bus, and when multiplied by the CPU multiplier, is the operating speed of the CPU. For a 1066 FSB the default number will be 267, for a 1333 FSB, the number will be 333.

So, CPU speed is a function of FSB and CPU multiplier. Take the Core 2 Quad Q6600, it has a FSB of 1066, and the default multiplier is x9. 267 x 9 = 2403, giving the CPU's default clock of 2.4gHz.

I would probably recommend flashing to the latest BIOS before beginning, especially if your board is using the original release BIOS. The BIOS version can be found in the BIOS itself, is usually annotated during POST, and can be found in CPUZ. Most motherboard manufacturers have a BIOS history on their website. Most motherboards have a utility to flash the BIOS from the Windows environment and will actually download the latest BIOS from the manufacturer's website. Though many people are afraid of using these utilities, preferring to use a thumb drive, or the old-fashioned method of making a bootable floppy, I think I have used the Windows flashing utility on each of the past 14 motherboards I have reviewed in the past year, and have never had an issue.

Failed Overclocks:

Before we get started, I want to mention one other thing, failed overclocks. I know it sounds like a bad thing, but it is a fact of life when overclocking. There are three basic reasons for a failed overclock: CPU instability, memory instability, or Northbridge instability. NB instability usually happens only when trying to attain high FSB rather than CPU speed. Memory instability occurs when increasing the memory speed along with the FSB, or when overclocking memory alone. Each of these has its own characteristics, and you can often tell what caused a failure by how the system behaves before and during the failure.

Today I will be overclocking only for increase of CPU speed, so CPU instability is hopefully the only issue I will have to deal with.

Crash-free BIOS:

In the past, the only way we had to deal with a failed overclock was to clear the CMOS or CCMOS, usually by removing power from the motherboard and shorting a jumper. This brought the BIOS completely back to its default state, and everything had to be reset: date/time, boot drive priority, everything. Today, most motherboards have some kind of system that brings the BIOS back to a semi-default state in case of a failed overclock. This awesome capability changes the face of overclocking by changing a failed overclock from a real pain to a minor annoyance by allowing you to go back in the BIOS, change the settings that caused the overclock to fail, never having to touch any other setting you have previously made. Some work better than others, but all I have used worked well.

Though one thing I have found is that the crash-free aspects often don't work when overclocking or tightening the timings on memory, so there still are instances when CCMOS is necessary.

So, let's get started…

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