OEM laptop has max CPU frequency capped when on battery

I was playing with a laptop from HP the last couple of days and noticed that when off AC power (on battery), the maximum CPU frequency is only half of the specification. The machine runs Windows Vista. The CPU is an AMD ZM-80, duo core 2.1GHz. On AC power, the processor can reach 2.1GHz on heavy load, but on battery power, the maximum it will go to is 1.05GHz on each core. This is really a problem because performance (especially for single-threaded applications) is pitiful at those levels. In fact, 1080p HD WMV demo videos could not play smoothly just like on a four-year-old Pentium M 1.6GHz.

This is apparently a common problem on a variety of laptops, especially as of late, see discussions at:

As usual, there is a bunch of crap on the internet about Vista or AMD being the culprit. No, this has nothing to do with Vista Power profiles, which are all set to 100% maximum processor state. After reading the above threads and thinking about this, I’m convinced that it is a system-level issue. When on battery power, something set in the BIOS must be throttling the CPU to half-speed, so any software controls will have no effect beyond that.

One of the threads did mention that turning off or altering a Power Management setting in the BIOS allowed the battery mode maximum CPU frequency to go higher. Unfortunately, I got a stupid InsydeH2O BIOS with nothing to set. The next step is perhaps to hack the BIOS.

Now for some entertainment:

Customer : CPU cannot go above 50% frequency when on battery power, no matter which Vista Power Plan is chosen.
[An agent will be with you shortly.][You are now chatting with Jarred .]
Jarred : Hello Customer
Jarred : Welcome to HP Total Care for HP notebooks. My name is Jarred. Please give me a few moments while I review your issue description details.
Customer : hello
Jarred : I understand that, your Notebook CPU does not go above 50% frequency on battery power. Am I right?
Customer : that is right
Jarred : I will certainly do my best to help you out with this information.
Customer : you can try it yourself
Jarred : Well Customer, let me inform you that this is normal for any Notebook that runs on battery power.
Customer : That is not normal, because I have another notebook (different manufacturer) that does not exhibit this behavior
Jarred : In these Notebook the settings are different, the Notebook does not run as it runs with AC power. Let me also inform you that if it Execeeds beyond 50% to 70% the Notebook will get freezed.
Customer : Frankly, that does not make any sense. Is this limitation documented anywhere?
Customer :And is there any way to get around it…
Jarred : May I know the processor if it is AMD or Intel?
Customer : It is an AMD ZM-80 processor
Customer : Turion X2 Ultra, for a TX2500Z build
Jarred : Well Customer in AMD process, there is a option set as ‘power no’, which will limit when running on battery.
Jarred : However you can try to check in BIOS if there is any option to change.
Customer : Do you mean PowerNow? I think that is certainly something that should be in the BIOS.
Customer : However, I checked the BIOS settings on this notebook, and there are very few options to change.
Customer : Do you offer a more sophisticated BIOS or an update that specifically lets me make this change?
Jarred : I am sorry it is powernow.
Jarred : Customer, i do understand your concern, I would have provided you right away, if there was any solution for this issue.
Customer : There are no power management options in the BIOS, unfortunately.
Customer : I believe this should be reported as a bug, because a 50% limit on the CPU on this notebook makes many online videos unplayable.
Customer : That makes this "Entertainment Notebook" very crippled on battery.
Customer : Can you open a support ticket with HP engineers to resolve this issue?
Jarred : Sure Customer, I will excalate a technical-exclation on this issue.
Jarred : If there is any advancement options provided you will be informed.
Customer : Will I get an email on the progress of this ticket?
Jarred : I need few details to do this.
Customer : Sure.
Jarred : Once if I create the case you will be intimated by email contacted by Phone once after this excalation is sent to the case managers.
Jarred : Untill then, you can have this chat session ID – XXXXX
Customer : Ok, I appreciate that.
Jarred : Please provide me Product Number p/n (eg:DS542U): Serial Number s/n (eg: CNS34915MC):
Customer : p/n: XXXXX
Customer : s/n: XXXXX
Jarred : Please provide me your shipping address and
phone number.

Customer : XXXXX
Customer : phone: XXXXX
Jarred : Thank you for the information you have

Customer : Sure.
Jarred : Okay Customer, I will create the case and you will be intimated by Email or by phone, by our case managers as soon as possible.
Customer : Thank you for your help. I appreciate it.
Jarred : Please let me know if there’s anything else I can assist you with, today?
Customer : That will be all.
Jarred : Thank you for contacting HP Total Care Support, please do not hesitate to contact us if you have any questions or clarifications. We assure you of our dedicated support, 24 hours, 365 days a year.
Bye Customer. Good Night.


  1. Leroy
    August 2nd, 2010 | 8:38

    Same scenario of problems I have. I own (Family and I) 7 laptops, 3 manufactured desktops, and 2 home builds. Not to mention the other electronics like TVs, stereos, mp3 players, etc… You call these support people (or chat online), they give you an “Americanized” name, but their accent is heavy (not American English). They always apologize for your problem, before they know what the problem is. They read from a script, to attempt resolution to your problem, but seldom come to a resolution. I’ve had Susie from East Asian, Bob, Chuck and Barbara from India(n), and a host of others from what I believe to be other countries. We buy those “quality” products, at a high price, but the manufacturer is paying for cheap labor (assembly and support), to fill their pockets, while pissing us off when we get pissed off at the people who are working to make money to support their families.—Something is amiss here! Yes– the support rep should be more knowledgeable of just about any issue that may arise with that company’s product! Then they would not be so eager or quick to “create a ticket” and “pass the buck” to another Susie, Bob, Chuck or Barbara. Because, we all know that Susie, Bob, Chuck or Barbara, will not be able to create another ticket, but may have to refer to their Supervisor, whose name may be Kim Lee, Hussad, Fatima or Mickial (get my drift?). By the way, my laptops are Toshiba, Dell, HP, Gateway and CompaQ. Desktops are Dells, except for homebuilds. TV is LG, JVC and Hitachi. Stereo is RCA, Panasonic and Sony. MP3 player is Apple, ilo, Zune and Creative. DSL box is an HG2701 Gateway. Added router is Belkin. As of yet, any of their Customer support reps have been somewhere else, unable to fully resolve all of my issues. R/S—just venting.

  2. July 25th, 2011 | 9:23

    I was looking for a resolution on HP 6530b screen issues that I get when running on AC (no battery). Came across this post. I have read quite a few posts on HP laptops/notebooks with a lot of complains. I am starting to not trust HP anymore! Unfortunately it is a little later for me to change my mind.

  3. November 2nd, 2012 | 21:25

    Hp is going outta business soon I hope!

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