The #1 source of Intel Core 2 confusion
It is doubtful that there is any other feature on Intel's popular Core 2 series of Dual, Quad and Extreme processors that has created more confusion and tech support calls than the outright bizarre CPU speed readout on the System Information screen of both Windows XP and Vista.
When you check your system you will see two frequencies, the first one is what you paid for and the second one is usually much lower. This leads new Core 2 users to wonder what that second lower setting means, if it's one core running at top speed and the other one crawling along, or exactly what the heck is going on.
The cause of all this confusion lies on Intel SpeedStep's DoorStep. As I recently explained in a Hub about a problem with AMD's version called Cool'n'Quiet these two monikers are each manufacturer's version of a "voltage and speed adjustment function that works on the fly depending on the particular load that the processor is under. Therefore, Cool'n'Quiet/SpeedStep will provide full processing power if the applications you are running demand them, such as 3D rendering, gameplaying, encoding and other CPU-heavy functions, but will automatically underclock and undervolt the processor if you're just web surfing, typing or performing other functions that don't require the full blown power of all your cores."
What happens on the System Information screen is that you are shown the full power potential of your Intel CPU in the first figure and what frequency the SpeedStep function has underclocked the processor at that point in time to reflect the load that you have your PC under. Therefore, if you were going to check the System Information at a time when you were encoding a video, applying a Photoshop filter on a huge image, and folding all at the same time, you'd likely see that the second number would match the first, showing that the CPU is running at 100% of its rated frequency.
If you are generally annoyed by this automatic underclocking and want to use up all the frequency your hard earned dollars paid for, you can shut down SpeedStep. This is where even more users run into trouble. They go into the Power Applet in Control Panel and select the Always On option. It is clear in the description that this will disable SpeedStep and provide for you every single Hertz you have at your disposal. So on XP (and similarly in Vista) they right click on the desktop, then click Properties, then click Screen Saver, then click Power button then change the Power Scheme to always on.
...and guess what? Nothing happens! It is one of SpeedStep's great deeply held secrets that in the majority of motherboards, you must have it turned off in the BIOS as well as in the Windows Control Panel!!! Before you go poking around your BIOS and mess up your PC to the point where it won't boot up any longer, check your motherboard manual for the exact procedure. When you're in there, don't change any other settings. You have been warned!
Fortunately, SpeedStep does not have the same problem that its AMD clone experiences with the top end Quad processors. While Cool'n'Quiet has been found to squash the performance of many newer Phenom CPUs, SpeedStep is a far better behaved specimen. But still... would it have hurt Intel to only need one process originated from within Windows to kill it rather than making users plunge into the sensitive innards of their BIOS?