Whats up with my CPU? - A SpeedStep F.A.Q.
So you've just set up your new PC, your playing around with it, salivating at all the technical details, when you happen to open CPU-Z or some similar program. Maybe you've overclocked it, maybe you haven't but either way you quickly realize that something seems, off. With in seconds you clue in that your CPU seems to be running slower than it should, underclocking itself and running at half the speed you paid for.
This CPU is a Q6600 overclocked to run at 3.4GHz, so wheres my missing 1.2GHz?!?!!!!1
So whats up? What wrong with your CPU? Nothing actually, its working exactly as intended. Its a little known feature called SpeedStep, which will down clock your voltages and multiplier whenever your computer is idle(low load) or not in use. Its actually quite an innovative feature, that saves electrical power, lowers your heat dump, and keeps your hydro bill down.
As usual Wikipedia explains it best;
There's my missing 1.2GHz! Go Go Rosetta @ Home!
Leave it On or Off?
So the next question usually is, how does this affect me, should I leave it on, or off? Well that depends, if your simply leaving your CPU at stock, I highly recommend you leave it alone, turning SpeedStep off will do nothing for you except higher hydro bills. In fact, even if your using an overclocked CPU, I would recommend to leave SpeedStep on, rarely, if ever, does SpeedStep cause stability issues, if your overclock is stable in the first place, then SpeedStep should not destabilize it.
On the other hand, if your in the process of overclocking, doing suiciding runs, or etc, and have not yet found a stable 24/7 overclock, then SpeedStep can cause issues. SpeedStep can make an unstable overclock seem stable, and a stable overclock seem unstable due to its constant shifting of voltage and multiplier settings.
Now onto the question still on everyone's minds, how does it affect performance?
Short answer; it doesn't, your computer will perform just as fast with it on as it does off. It ramps up the speed so quickly that any performance intensive program(Gaming, Rendering, Folding, Crunching, etc) will not even know that your CPU was running at half its speed only moments ago.
Longer answer; sometimes it can be, for example in a few synthetic benchmarks such as SuperPi in which milliseconds matter, the slight(VERY SLIGHT) time in which it(SpeedStep) takes to ramp up can affect the resulting, resulting in a slower posted time. Real world applications, and even most benchmarks, simply aren't affected by the time(minuscule as it is) that it take to ramp up, but it is worth mentioning as there are a few (rare) cases such as SuperPi where SpeedStep can adversely affect the performance.
Other Points to Consider
One last thing that must be brought up and that is, C1E. C1E is a feature that works as a part of SpeedStep, but it is NOT SpeedStep, nor technically part of it. If you are running an overclocked CPU, no matter how stable, I would HIGHLY recommend turning it off in BIOS. The reason for this is simple, C1E likes to play with your Voltage settings, ALOT.
As plenty of us know, at times its an art finding voltage settings that an overclocked CPU likes and is stable at. The issue with C1E is that it will drop your voltage down, and unlike SpeedStep which is almost instantaneous, C1E takes a few extra milliseconds to kick in. While not an usually an issue when a CPU is at stock clocks and voltages, it can be devastating to the stability of an overclocked CPU, as they are more sensitive to voltage changes.
How do I turn it off?
If you still feel the need to disable SpeedStep, read on for a step by step guide on how to disable it in BIOS(hardware) and/or Windows(software).
How to "disable" SpeedStep in Software
"Disabling" SpeedStep in Windows XP
"Disabling" SpeedStep in Windows Vista/Seven*
*As of Seven RC1, the steps provided below are the same, however the windows do look slightly different.
Go to your control panel and open "Power Options"
Next, regardless of which powerplan your on(though I recommend "High performance" for a desktop PC) hit "Change plan settings"
Hit "Change advanced power settings"
This will open the advanced options(go figure :bleh:), scroll down to the "Processor power management"
Open and change "Minimum processor state" and "Maximum processor state" both to 100%
Hit Apply and Okay to everything and your done!
How to disable SpeedStep in Hardware
It's about time!!!!! (Thanks a ton for this, I know a certain poster who we all hope might be able to cut down his meds now.... :) ).
Ooops... let me know if you need this space and I'll delete..... :)
Alright guys! Feel free to let me know if there is anything that needs fixing or clarifying, I'm sure that the guide is not perfect(yet!), so I could use all the criticism on making it better!
I hope that this helped expand your knowledge of how Intel's SpeedStep works, feel free to ask any questions, and I will do my best to answer them.
Great job chilly, one possible suggestions is another colour for the text above the pictures thats a tough read even for us young guys with not as bad eye sight as the ol'wise ones around here.
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