Slow CPU Clock while on AC Power (requires reboot to fix)

[dt126]

Hello:

I haven't used this laptop much the past year and when I did it seemed slow. I was on a trip recently and finally put the effort into figuring it out and I'm seeing rather odd but very consistent behavior.

When I boot on battery, the system works very well. If I'm watching the CPU, it will typically be running in the 8X to 29X multiplier range (up to about 2,900 MHz). As soon as I plug in the AC charger, the CPU clock drops instantly to 498.99 MHz (5X multiplier). It stays at eactly this speed continuously and typically the CPU stays loaded at 100% (since it's operating so slowly).

If I unplug the AC Charger, it improves a little bit to either an 8X or 9X multiplier (just under 900 MHz max). However, even though I am back on battery, it will never improve beyond this level until I reboot on battery (then I'm back up running in the 2900 MHz range).

I have read other posts (from HP and other laptops) that similar behavior sometimes happens with under-powered chargers, but I have both the OEM and an aftermarket charger and they both cause the same issue. I did not have this issue when I originally bought the laptop.

Here is what I have tried:

1) Every possible power plan option under Win 10 I can think of. I've reset the plans and mainly use HP Balanced.

2) Updated Bios (twice, now at F.51 (6/8/2018)

3) Continually update Windows 10

4) Run HP’s support assistant – no available updates shown

5) Changed the power plan in the BIOS (only two options)

The only thing I haven’t tried is to manually download all current drivers from the HP website and install them but that’s probably my next step. I’m sure that the problem is something related to power management so maybe something with the Intel chipset driver?

Any advice or suggestions? Thanks.

[Jeet_singh]

@dt126,

Thank you for reachhing out to us on HP Support Forums! I see from your post that you are having issues related to HP Spectre notebook. Don't worry we'll work together to help you resolve this issue.

Splendid effort and fabulous description of the issue before posting. Kudos to you on that score.  You are a valued HP customer and it is paramount to assist you here. I take it as a privilege to share this platform with you. 

To proviide you with an accurate solution, I'll need a few more details:

Are you using the original HP Charger that came with the PC? Have you tried to use an compatible higher capacity charger to check if the issue persists

In the meantime, let's try these steps here: 

Perform a Hard reset on the notebook: 

Many startup errors and other problems can be resolved by decreasing the amount of power stored in hardware components. Decreasing stored power is sometimes referred to as a "Hard Reset". Use the following steps to perform a hard reset on a computer:

1. If Windows is open, click Start and then Shutdown.

If Windows is not open and the computer has power, press and hold the power button on the computer until the computer shuts off.

1. With the power off, disconnect the power cord from the back of the computer.
2. With the power off and the power cord disconnected, press the power button on the computer for 5 seconds. The power light indicator on or near the power button might turn on briefly but then go out.
3. Reconnect the power cord and turn on the power.

Adapter will never be as fast as the battery because the battery is a DC element and adapter has to convert from AC to DC and then transmit the power to battery and to PC to run. So Adapter will take more load than the battery.

If you are comfortable, you can try to replace the CMOS battery on the PC and check if that helps.

Alternatively, as you suggested you can try to update the drivers manually and try to update the Chipset drivers, on your PC from our HP support website, using this link.

Please let me know if this resolves the issue, or if you require further assistance!

Eagerly waiting for your response!

Give us some reinforcement by clicking the solution and kudos buttons,

That’ll help us and others see that we’ve got the answers!

Good Luck

[dt126]

Hello Jeet:

Thank you for your response.

1) I tried the hard reboot you mentioned, no effect.

2) I have not yet tried re-installing chipset drivers. I will do that after I've gotten your response to this email if you still want me to.

3) I ran the component diagnostics (from F2 on boot) on the AC Adapter and received the following Warning message, "The Smart Adapter feature failed to return valid data." I am not sure if this indicates an issue or if the Smart Adapter feature isn't present on my particular laptop. I have the original adpater (P/N  740015-002, 45W, 19.5VDC, 2.31A DC). I also have an aftermarket adapter with the same spec's and it gives me the same warning on this diagnostic.

4) You asked if I had a higher power adapter. I do not, but I would be happy to buy one. I noticed on the back of the laptop that after the 19.5VDC, it lists 2.31A/3.33A. This would correspond to 45W/65W. If there IS a 65W power adpater that is compatible with this laptop, please give me the part number and I will order one and see if it works.

5) In the past, both AC Adapters functioned normally. 

6) You mentioned that the laptop will always run faster on battery. This may be the case with the Scpetre product line but it certainly wouldn't be a valid statement about laptops in general. I've run prior laptops without their batteries (as file or media servers) and they functioned just fine off of an AC adapter. As long as the adapter is providing the required DC voltage and can supply the required amount of power there should be no issues.

7) If this laptop series DOES run slower on AC Power how much slower should it run? If it dropped by 25% or 30%, I wouldn't see that as a major issue (but it would be good to know). However, it's now dropping by moire than 80% and that isn't acceptable for a machine to be usable especially when it wasn;t always like this.

😎 I'd have no problem changing the CMOS battery but how could this help with this issue?

9) Is there any way to send me an old FW version (from 2-3 years ago) that I could test-flash? I'd be interested to see if something in the factory power management was adjusted in the BIOS or if it's Win 10 or my charger. This might be helpful.

Thank you.

[Jeet_singh]

@dt126,

It's great to have you back and your patience is greatly appreciated.

In this scenario, there are two things that you can try. 

1. Try with an higher capacity adapter - For more details, I would suggest you try to https://support.hp.com/ - 

Please enter the product number or model number of the notebook, On the left pane click on User guide on the Right click on Maintenance and Service guide.

Here on the Maintenance and Service guide, please scroll to Chapter 3. Illustrated parts catalog, Here you will have the list of compatible and tested parts for your PC.

From the list choose the Adapter and If you wish you could purchase the part from HP, use the HP Parts surfer to identify the part: http://partsurfer.hp.com/search.aspx 

And order it via the HP Parts store: https://parts.hp.com/hpparts/CountryChoice.aspx?mscssid=&ccode=ZZ&lcode=ZZ 

Next thing, as you mentioned, please try to update the drivers and chipset and check if that helps.

Let me know how it goes for further assistance.

Regards,

[dt126]

Hello Jeet:

It seems like HP's website is undergoing some upgrades. I haven't been able to access the portion of the support site where I can look up parts for the past two days and I get this message, "HP Customer Support site is temporarily unavailable."

However, I have done some more testing and figured out quite a lot. First, I re-installed the chipset drivers. No luck with that.

Then I installed the program, Throttlestop, and was able to troubleshoot the issue. When the AC adapter is plugged in, the system is using the BD PROCHOT signal to throttle down the CPU. I don't know if this is because it's somehow able to very rapidly test the power output of the charger (45W vs 65W) or if it is using some type of "smart" tech in to communicate with the charger (which I mentioned in an earlier email). Regardless, this action forces the CPU down to 5X clock (about 500 Mhz) and it stays there. When unplugged, the signal goes away but the CPU only recovers to 8X or 9X clock ( ~900 MHz).

After I diagnosed this, I was able to block this signal using the same software and the laptop runs normally on AC power (up to 3.0 GHz). There seems to be no issue whatsoever in terms of power or temps from the 45W charger. I tested for about 4 hours using a variety of CPU stressing programs and everything is functioning normally. The CPU thermal throttling is functioning normally, so there is no overheating and the 45 W charger is able to supply enough power for the computer to function while charging the battery.

I’m not really sure what to make of this and I’m hoping that you can discuss it with someone in the engineering team. I'd really prefer not to block this signal as HP could also be using it for other purposes, such as downclocking the CPU if the GPU temps spike. 

Before I investigate a 65W charger as a solution, please tell me if this downclocking is happening to me because the system is somehow sensing the capacity of the charger OR if it is trying to detect an OEM charger (and perhaps my charger/cable is now defective and failing this test). I discovered that Dell takes this approach with some of their laptops.

Based on my testing I’m really not sure if I even need another power supply. It kind of feels like a miscommunication in the engineering/BIOS team. For example, someone might have wanted to provide some added headroom with a 45W charger and told the team to throttle the CPU BY 20% but instead they coded it to throttle TO 20% (meaning 80% reduction in speed).

Please review and follow up with me. Thanks.

[Flower_Bud]

@dt126

Thank you for responding,

It's great to have you back 😉

It looks like you were interacting with @Jeet_singh, but he is out for the day & I'll be glad to help you out,

I'm the Flower_Bud & I'm at your service.

I will send you a private message to assist you with the next course of action. Please check your forum private message box next to the bell notification icon on the upper right-hand corner for a private message from me for further assistance.