Are your CPUs running slowly? Tool tip and survey

(Yes, I know I haven’t editorialized the last survey on What’s in a Job Title – I will in the New Year.)

Over the last couple of weeks I’ve signed up a bunch of new customers for maintenance/ops audits and general perf work and I’ve had all of them check whether power saving mode is enabled for their CPUs. And I’ve been astounded by the results – as have some of the customers who thought they were running at full speed all the time.

In a nutshell, to save power the CPUs can essentially down-shift to a lower clock speed and then automatically speed up again when the load increases. But at what point do they speed up? That varies – you might have to really push things to make them speed up.

And do you really want your workload running slower until the CPU usage hits the magic speed-up threshold? Most likely the answer is no.

So the point of this blog post – I’d like you to go check the CPU speeds on your systems and see whether they’re in power-saving mode without you knowing. I think you’ll be surprised. And then I want you to tell me what you saw.

You can check the CPU speed using the free CPU-Z tool – it’s awesome. It’s just asks the CPU it’s speed – no load is put on the system.

The picture below shows a CPU-Z snapshot from a client system. The CPUs are spec’d at 2.4GHz but as you can see, they’re only running at 1.2GHz – half speed.


Go download the tool and run it on your system – what did you see?

I’ll report on the results in a few weeks. [Edit: The survey results can be found HERE.]

You can another read example of this problem in a blog post by Brent Ozar (“SQL Server on Power-Saving CPUs? Not So Fast.“) about helping Stack Overflow upgrade.

Have fun!

PS There’s also a KB article that discusses how Windows Server 2008 R2 sets the Balanced power plan by default! See here.

5 thoughts on “Are your CPUs running slowly? Tool tip and survey

  1. Now this is interesting…

    I ran this on my desktop (not having a server around to test on) and found that my Core-2 Quad CPU (2.4GHz) is running sometimes at 1.6 GHz. Don’t think I’m going to change it, because quick testing shows that the speed does go up to 2.4 as soon as there’s even the slightest load on the machine

  2. The desktop is in a custom high performance plan all the time (min CPU 100%, max CPU 100%, do not power disks down). I have it that way because I often leave the machine doing heavy CPU crunching while I’m elsewhere and I noticed on Vista that it would power the disks down because there was no user input, even though the CPU was at max. It’s just that the EIST (speedstep) is still enabled in the bios. By the looks of things the CPU’s at 1.6 (x6 multiplier) when idle and up to 2.4 (x9) with any load (even opening Word)

    I’ll pay more attention after upgrade, as this machine’s going to get an i7 early in the new year.

  3. Sadly, this will continue to be a problem as major vendors (Dell/HP/IBM) continue to ship servers with BIOS settings that enable ‘power stepping’ on Servers by default.

    Dell, for example, sells all of their 11G servers with C States enabled (meaning that your procs/cores can be put into lower power mode):

    Full Reference:

    Ironically, they frequently do the INVERSE for laptops (where you’d think that you’d probably WANT the ability to sleep in order to conserve power): (or:

  4. Want to run fast during the day and still save the planet?

    Changing power plans is a painful process, requiring numerous mouse clicks and navigation. Make this easier by installing the Power Scheme gadget ( and you can switch modes with a single click.

    Worried that you’ll forget and leave your system in high-power mode all night? Get a macro scheduling tool like KeyText ( and configure a macro to run after you leave at night (or after your automated processes and backups finish) to minimize all applications (Windows-D) and then send the click to the Power Scheme gadget to put your system back in low power mode.

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