I overclocked my I5-3570K to 4.2Ghz. I noticed that on CPU-Z my CPU speed didn't stay at 4.2GHz. It went all the way down to 16GHz. The multiplier on CPU-Z also says (16-42). How do I make it stay at 4.2GHz?
You can disable C1E in the BIOS. What you seeing is the result of SpeedStep, which lowers power usage when you are not working the computer hard. However, if it goes back up to 4.2 GHz when running a high load, I'd leave it alone. It won't hurt anything.
That's intended behavior. CPUs downclock to save on power. It should ramp up to 4.2 GHz under load and idle at 1.6 GHz normally (like when browsing the web).
You can disable C1E in the BIOS. What you seeing is the result of SpeedStep, which lowers power usage when you are not working the computer hard. However, if it goes back up to 4.2 GHz when running a high load, I'd leave it alone. It won't hurt anything.
You should be able to disable the power saving features to force it to run full speed all the time, but I don't see why anyone would want to -- it's just going to use more power and create more heat.