Questions about i5-4200U/i7-4500U and Turbo Boost

I think the concept of Turbo Boost might be a little lost on me... I thought that using this technology, processors "overclock" themselves when there is a higher demand, and otherwise, they work around their base-frequency. I saw a laptop with a i5-4200U (1.6-2.6 GHz) on display, and when I checked the CPU usage from the task manager, the CPU was running at 2.4 GHz! Surely, despite the bloatware running, there couldn't be that much of a demand on the CPU that it had to almost run at it's maximum frequency, right? I talked to a salesperson, and he said this was because of the laptop being plugged in and running on high performance mode rather than a battery saving mode. He switched it to battery saver mode and the frequency fell to .76 GHz. I suppose what he said made sense, but 2.4 GHz, even on high performance (with the laptop pretty much idle) still seems rather high, right? Or am I just being an idiot?

Also, in the task manager (under the CPU usage tab), there was a maximum speed stated for the i5-4200U laptop which was 2.3 GHz, and it was 2.4 GHz for the i7-4500U. Why did I see these numbers on task manager when those processors are supposed to have a maximum speed of 2.6 GHz and 3.0 GHz respectively with Turbo Boost? =\ This was especially strange because the i5-4200U was initially running at 2.4 GHz, which was above it's maximum (as defined by the task manager)! Can someone please help me make sense of this all?

I know these questions might be a bit elementary and stupid, but please bear with me. Thanks!

 

CPU's boost to different speeds depending on how many cores are being used. The max advertised speed is the max speed with a single core being active, the speed progressively scales down with number of cores or threads, and even then it boosts to within TDP limits, and may only hit that max speed (if at all) for only a few seconds then as heat rises, speed drops to remain within TDP limits. For lack of a better term TDP is heat energy/temperature. Think of it this way, it's better to use a little more energy with a boost of speed to get tasks done more quickly, than running with slightly less power but for an extended duration, which likely results in more power used, to do the same amount of work. Some refer to it as "race to idle".

Don't look at the speed, look at the CPU usage. If it's 2.4GHz 100% usage then yes, it's high. Otherwise, the laptop is likely set to high performance in power options which sets the CPU to run at its fastest state depending on cores being used. This shows my CPU at 3.3GHz but 0% usage. It's not consuming any more power, well maybe a teensy bit more, to run at that speed with doing next to no work than it is running at 800MHz and doing no work.




Notice CPU is set at 100% for both minimum and maximum processor state, which means max boost depending on how many cores being used. If you unplug it, it either switches to balanced or power saver mode automatically, or uses the "on battery" profile or it's some fixed intrinsic CPU speed that is coded in the BIOS. All depending on the manufacturer.

 

Oh okay, I get it now! Thanks!

Although, my second question remains unanswered, I think... What does the "maximum speed" refer to exactly in CPU tab in the task manager? If you were to click the CPU tab in your screenshot, you'd be shown a "Maximum speed" where it currently says "Speed: 1876MHz". What is this maximum speed? I understand now that the advertised maximum speed (2.6 GHz for the i5-4200) can't be achieved viably by all cores due to temperature issues, but that doesn't explain what this figure that task manage is showing is referring to.

 

"Maximum Speed" is really just rated speed. If you turn off turbo boost, it won't run any faster than that.

 

Oh, gotcha! That's it then. Thanks for all your help! ^^