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This is a little FAQ on C1E, EIST and SpeedStep in general. Since this question gets asked so much, I thought it would be a good idea to post a definitive answer on the subject.

Why is my processor running slower than I told it to in the BIOS?

This question is perhaps the most commonly asked of all here on the OCN forums. Many young overclockers eagerly increase their BIOS settings, only to boot into Windows and find that their CPU is considerably slower than it should be. On top of that, its speed jumps up and down. What causes this phenomenon, and how can it be fixed?

The issue at work here is thanks to Intel's SpeedStep technology - a handy feature implemented in all of their new CPUs. SpeedStep is a function that detects how much work your processor is doing, and lowers or raises its speed based on that reading. This means that when your processor is idle, or performing simple tasks like browsing OCN, it will run slower. When it's benching, stability testing, gaming, video encoding and such, its speed drastically increases to provide the best performance. Let's look at an example:

You've set your machine up to run with an FSB of 450, and your processor has multipliers between 6 and 9. While idle, your processor will run at 450 * 6 = 2.7 GHz. Under load, it will automatically boost up to 450 * 9 = 4.05 GHz! That's a huge difference, and you can see why it can be useful. 4.05 GHz is a considerable speed to achieve on any processor, and takes a lot of power to run. When you're checking email, you don't need 4.05 GHz of speed, so SpeedStep lowers it to a lesser state. This way, your system saves power, runs cooler, and puts less strain on all of the components - meaning that they last longer.

Let's look at how it works. SpeedStep has two key components:

C1E (Enhanced Halt State): C1E is the simpler of the two components. It can be enabled or disabled in the BIOS, and performs independently of the operating system. C1E has two configurations - idle, and load. When CPU usage is relatively low, this feature lowers your processor's multiplier to its lowest setting (usually 6x) and slightly lowers its vCore. During a CPU-intensive application, it will raise the multipler to its maximum value, and will provide a small boost in vCore to compensate. In our example, C1E will make your processor run at either 6x or 9x the FSB.

EIST (Enhanced Intel SpeedStep Technology): This is a very robust feature and has a wide variety of power-saving capabilities. Like its simpler cousin, EIST can affect both your CPU's voltage and it's multiplier - however, it has many more levels of configuration. Instead of a simple "slow or fast" setting, SpeedStep can utilize all of the available multipliers. In our example case, EIST will allow your processor to run with a multiplier of 6, 7, 8, or 9, and chooses which one to use based on how much demand your CPU is under. EIST is controlled by Windows, and utilizes the different "power schemes" you may have seen in your control panel.

Great - so what does that mean for overclocking?

Many overclockers, both new and experienced, prefer to simply leave these settings disabled. Sometimes the constant adjusting multipliers and voltages cause instability in their overclocks, other times they just prefer to see their components running as fast as possible all of the time. If you are among them in either case, then feel free to disable both C1E and EIST in the BIOS. Once you stabilize your overclock, and you find you'd like to enable one or both of the features, it's always a good idea to re-test your stability once they've been activated, just to make sure that they won't cause any problems.

Here's a discussion about them if you care to read more.
 

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Argh, thank you so much. I see to many threads asking why their multiplier gets bunked and stuff, when the simple answer is that their CPU technologies need to be disabled to get an overclock to work right. + REP
 

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PC Gamer
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When you're checking email, you don't need 4.05 GHz of speed

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damn then why did i overclock this thing?

haha just joking
 

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Premium Member
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I was actually in the process of writing a guide for this lol but good job


Another sticky request, and rep+
 

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PC Evangelist
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48,330 Posts
Nice Guide.
 
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