Please note: This was written for publication on a non-computer blog, and as such is very elementary. Since I am a complete newbie, it makes sense to me. If you have been doing this for more than a month, you will think this sounds very lame. You're right, but please bear with me because everyone was a newbie once. Thanks for your patience.
And now... the final post in this series...
What is overclocking? Overclocking is the practice of operating a computer component above its rated specifications. Why overclock? There are two main reasons: (1) for the challenge of it – as a hobby or competitive pursuit, and (2) to increase the ratio of performance per dollar expended. In my case, I wanted to do it for both reasons, but mainly to see if I could do it and learn how it was done. You may think this is a dangerous game to play with an expensive new computer, and you would be right. Therefore, I approached it cautiously with self-imposed limitations designed to protect me from myself.
I bought a factory-overclocked graphics card, so I was not interested in overclocking it further. My reasoning for ignoring this popular option was related to performance in games. I currently had no games that would stress the GTX285, and I was not likely to buy any in the near future. My future plan to deal with graphics bottlenecks involves a second GTX285 in SLI mode. It will certainly be more expensive, but more effective as well. So there was no reason to push this card and add a variable to the already-uncertain proposition at hand. That leaves the CPU as the primary target.
I was interested in overclocking the CPU to a reasonable goal of 3.5GHz. The Core i7 is a relatively new chip (introduced to the market in late 2008), so there are not too many articles published on overclocking it yet. I read most of them, and they typically overclocked the Core i7 920 to a frequency of 3.8-4.0GHz. I felt 3.5GHz was a conservative target, achievable without a great deal of skill or risk. I read a couple of articles about overclocking my particular motherboard, including one written by Gigabyte. It sounded pretty easy, so I jumped in to the shallow end of the pool.
The basic strategy for overclocking a Core i7 processor starts with increasing the base clock speed of the chip. The stock clock speed of the 920 is 133MHz. The multiplier of the chip is locked by Intel to a maximum value of 20 (but it can be lowered). The resulting stock frequency of the CPU is 2.66GHz (133x20). An overclock to 3.0GHz can be achieved by increasing the clock speed to 150MHz (150x20=3000). That’s where I decided to start, with an ultimate target of 175x20=3.5GHz.
Overclocking is performed by changing values for clock speed and other parameters in the bios. As the operating specs of a component are increased beyond their stock performance, the components may need more voltage. Too little voltage can result in a failure to boot, while too much voltage can damage components over time (or even immediately in extreme cases). Fortunately for me, Gigabyte provides software to help you do this balancing act.
EasyTune6 is a monitoring application that provides operational information about the computer, and it includes a one-step overclocking tool (for dummies). You select the target CPU frequency, and the software makes the appropriate changes in the bios. The clock speed will be set to the proper value and other critical parameters, such as voltage, will be changed using “auto” settings in the bios.
Auto settings are frowned upon by overclockers because these settings typically result in too much voltage, causing overheating and ultimately limiting the top end of the achievable overclock frequency. In my case, that would not be an issue given my low target, so I felt it was safer to go this route rather than supply my own values and possibly nuke the system.
I selected the 3.0GHz setting and rebooted the system. It came up just fine and a check of the EasyTune6 display showed that I had indeed achieved my first overclock. However, the CPU was running at 3.15GHz. Did I click the wrong button by mistake?
A little research revealed my newbie mistake – turning on the “Turbo” performance-boosting option in the bios adds 1 to the multiplier. Since I had enabled this option initially and the auto settings don’t turn things like that off, I was now really overclocking at 150x21=3150. This oversight was not a problem for my baby-step attempt, but it was a good learning exercise.
I checked the temperatures with CPUID Hardware Monitor, and found them to be a little warmer than before but barely so. EasyTune6 showed the CPU voltage had been increased to 1.40v, which is comfortably within the parameters of the chip. The motherboard CPU voltage LED was showing yellow (meaning “caution”) but not red (meaning “stop, you idiot”). A 4.0GHz overclock had been achieved by others with this amount of voltage, so I made note to manually try a lower CPU voltage later. I could not get values for the memory and motherboard voltages from the software, but the respective motherboard LED’s showed green – meaning only slightly increased over stock – so I considered them safe.
The free multiplier point from “Turbo” caused me to think about my target base clock speed. At this point, it is necessary to explain how the remainder of the system is affected by the overclock of the CPU. In a Core i7 motherboard, the bus (FSB) has been replaced with QPI (Quick Path Interface). The memory operates on its own multiplier with a separate path. The QPI and memory speed automatically scale as the base clock speed is increased. A check of the bios revealed that the software had done this for me.
The stock memory multiplier is 8, resulting in a stock memory speed for a Core i7 920 of 1066MHz (133x8). However, my memory is rated to run at 1333MHz, so I could scale up to the rated memory speed with the stock multiplier and a base clock speed of 167 (167x8=1336). The base clock of 167 with Turbo enabled, would give me a CPU frequency of 3.5GHz (167x21).
The synergy of this was just so appealing to me, mainly because I am a Libra (balance, scales, you know…). So I decided to go for 167x21 rather than 175x20. I pushed the clock speed up in two stages – 160 via the EasyTune6 application (its maximum value) and then the final 167 via the bios itself while setting the CPU voltage manually to 1.40.
It booted fine on both settings and an hour of World of Warcraft was completed without incident. The temperatures at load were well within tolerable range… CPU in the high 50’s C and graphics in the mid 70’s C. I communicated my success to my advisor, and he responded with a good question… is it stable? Err… well… it’s not giving off flame or smoke… I guess that’s ok, right?
He explained that I needed to test the overclock by stressing the system beyond what it would normally see. He recommended a program called OCCT, which basically loads all cores of the CPU to 100% for however long you desire. The test also puts load on the memory and QPI to give you a view of how your system will survive extreme loads in operation. It either completes the tests, or it fails and you adjust your overclock and try again. I ran OCCT first for one hour and then eight hours, and all tests were completed without errors. So I declared myself stable… well, my computer anyway.
I was seeing temps in the mid 70’s C for the CPU, which is not bad, but I set out to see if I could lower them. I reduced the CPU voltage in baby steps, checking stability each time, to a value of 1.35v. I moved a few cables inside my case to improve airflow from my intake fans. I turned the case top exhaust fan up to medium, which did not appreciably increase noise since it is a very quiet 200mm fan. Finally, I replaced the conventional light bulb in my desk lamp with a compact fluorescent bulb, which lowered the ambient temperature at my desk by two degrees! These changes combined to allow me to reduce load temps to just below 70C.
That’s my current status, but there are always further improvements to be made. My list of ideas include reducing the CPU voltage even further, changing some of the other voltages (memory and QPI) to manual values and then finding their lower limits, and turning off some of the energy management features of the motherboard to see the effect. The goal of these changes is to further reduce temps and theoretically increase the life of the components. I haven’t quite decided how to approach these changes, so I am just enjoying the system while I continue to monitor for possible problems. After all, the system is only two weeks old.
So I did it… I am an “overclocker”… albeit a somewhat lame one with only a 33% overclock to show for it. Bragging rights start at 50%, but that wasn’t the point for me. I accomplished exactly what I had set out to do – I increased the performance of my system without turning it into a brick and I learned a lot in the process.
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