HP AIO, cpu locked at .8Ghz

[Big Jim]

HP All in One.
Wouldn't power on when it came in to us, but when the PSU was attached it did light up a power LED on the back of the PC

so I ordered a 2nd hand board off ebay and when it came it was the same.

I tested the PSU and power switch with a multimeter and both appeared ok.

However swapped the PSU for our shop universal one and it powered up, straight away, both boards are the same.
CPU is an i5 Haswell, I have swapped in another i3 Haswell chip and its exactly the same.

tried updating drivers and BIOS on both boards but, tried a completely fresh install of W10 (this has 8.1 on it)

BIOS is a typical HP bios (ie really really limited options)
there are a few options that point towards power management but none of them actually have any effect.

EDIT: HWInfo 64 is telling me that PROCHOT is reading "YES", but cpu temp at the moment is around 30oC

EDIT2: found a program called throttlestop which can remove the BD PROCHOT trigger which restores the CPU speed, but its not really a great solution as the fix needs reapplying after every reboot and the program always runs in the taskbar (as a pose to system tray only)

Any kind of monitoring software only reports CPU temps, HP obviously doesn't allow OS access to this data,

Is it possible the faulty PSU has popped something on both boards causing this issue ?
I can't see any signs of burnt/blown components

 

[fincoder]

However swapped the PSU for our shop universal one and it powered up, straight away, both boards are the same

Doesn't the above statement say you fixed it by changing the PSU? What exactly is the rest of the post trying to fix? Is the performance too slow?

 

[HCHTech]

Doesn't the above statement say you fixed it by changing the PSU?

He got it to boot up by replacing the power supply, only to discover CPU was now locked at 800MHz. I couldn't quite follow the order of parts tried, before or after the PS swap, so not sure what to recommend next.

 

[fincoder]

He got it to boot up by replacing the power supply, only to discover CPU was now locked at 800MHz

Sure, I figured that might be what Jim was trying to say.

Big Jim:
Does it feel slow? If it feels fast enough then the throttling issue is theoretical only, could be a red-herring.
Are you sure it wasn't like that before the PSU issue? Might be a design fault in that model.
Is it a desktop Haswell or a u-series laptop Haswell? Some AIOs have laptop processors.

 

[GreyWolf]

With the tool you mentioned "throttlestop" I'm guessing this might be a post to be shipped in TEO as you can cause some serious damage if you have no clue on how to use it. @Kraken

 

[Big Jim]

I'll post the order of events as accurately as i can to try and clear up the confusion

1 - replaced motherboard
2 - replaced psu (like for like 90w for 90w), computer booted

gave back to customer, customer complains it is running slow
I check it out and cpu has been throttled to 800mhz (actual not just bad reporting)

3 - update drivers, update bios, clean install of Windows 10, no change
4 - try alternate CPU no change

Further digging reveals that something is sending BD PROCHOT command to cpu in order to trigger it to throttle.
I then found out about throttlestop which enables you to remove the BD PROCHOT trigger.
PC runs fine but requires throttlestop to be re-run at every bootup otherwise cpu is throttled back to 800mhz.


so research tells me that BD PROCHOT can be triggered by any component, it is essentially a way for a component to cool itself since the cpu is the biggest source of heat/power draw in the system by throttling it down to its minimum speed it will also cool whatever else is having the problem.

I have no doubt in my mind that something is overheating, it cant be as it happens straight from a cold boot, my theory is either
1 - the customers bad PSU has blown something on both boards
or
2 - the replacement PSUs are not up to the job.


I doubt its 2 because although the bad PSU wont power the pc on, it is still delivering 19.5v, and my spare PSUs (generic universal) all deliver as near as damnit the same voltage.

I have ordered another board from ebay, hopefully that cures the issue.

 

[GreyWolf]

Holly Crap if this is the fix that I found what the heck are they building as systems.

https://h30434.www3.hp.com/t5/Noteb...s/Suddenly-lagging-laptop/td-p/5915580/page/4

Your weather in your area and a sensor on the board may be causing the issue and it is quite possible the environment that it is in. They explain a fix for laptops but I'm sure you could fool the system in sleep mode to cause the same fix.

 

[Porthos]

HP All in One.

What Model?

 

[fincoder]

1 - the customers bad PSU has blown something on both boards

Does the throttling problem occur on the original board? The original problem was just the faulty PSU so you could try the original motherboard again.

If it's only a 90w PSU then it must be a laptop CPU in a slim AIO (assumed because there is still no mention of the CPU or PC model). Some very cheap AIO PCs might be deliberately designed to throttle the CPU to keep the TDP lower (to reduce cooling hardware bulk and cost).

Maybe it's just a slightly wonky re-assembly causing the cooling system to be less effective.

Maybe the throttling problem is relatively common and the motherboards that have the issue are ending up on ebay.

 

[Big Jim]

the PSU is indeed an external laptop one.

as i said both boards are the same, they throttle the cpu.

customer reports performance was ok prior to psu replacement.

model = HP23-p030na

 

[Big Jim]

so the new board arrived and we just tested it and the CPU is still throttled to 800mhz. not quite sure what I can do now apart from offer the software as a solution to remove the throttle.

 

[mikeroq]

What processor is in there? Specs for this model show a 35W i5-4590t and a 90W power adapter.

What was the i3 you put in? This model only supports 35-45W processors (T series):

 

[pcpete]

Is there a temp sensor plugged into the motherboard that may be faulty? Try a larger more powerful psu to rule that out. If these things were already mentioned I apologize

 

[Big Jim]

the CPU that was in it was fine, the problem only happened after changing the PSU, we tried the one we use in our shop I even ordered another one from Amazon (3rd party but to the exact spec of the HP original one) and it was all the same
I gave up on it, I know its a bit of a cop-out solution but went with throttlestop.
Although that solution failed when his 10 year old daughter reset windows. GRRR.