Intel Core Ultra 7 155H Issues

DHR · Jun 17, 2025

I've not used ThrottleStop yet nor tried to, but I'm having big issues with a number of 155H CPUs.

Intel base clock is 1.4Ghz and they can boost to 4Ghz+ however I'm having issues where after a period of uptime the processor refuses to boost and sticks at below 1Ghz, even being reported in Windows 11 as well under 1Ghz at times. Until it's restarted it stays like that.

Hammering the device with prime, cinebench etc. when it's like this won't even cause enough heat for the fans to kick in, there's no heat, the CPU is just doing what it can with what little its got, thermals all come back cool as.

Reboot it, rerun the same benchmark, the CPU boosts to 4Ghz no problem, fans whirring as expected and heat generated, it's scores 80% more than what it did moments before. Cinebench for instance failed to get through one pass, after the restart it completes 2 or more.

Genuinely scratching my head on this one!

unclewebb · Jun 18, 2025

Posr some ThrottleStop screenshots when your CPU is in limp mode. Include the FIVR and TPL windows so I can see your settings.

Open up Limit Reasons. Is anything glowing red to indicate the reason for throttling?

Run a light load like a couple of threads of the TS Bench test.

What laptop model do you have?

DHR · Jun 18, 2025

Will do thanks @unclewebb, it's the latest HP ZBook Firefly. It occurs periodically but at random junctures so I'll report back as soon as I can.

DHR · Jul 2, 2025

Well it's taken a lot longer than I would have liked to get to getting this data gathered - I'm just pulling together screenshots now @unclewebb with two systems side by side I'll post shortly.

It looks to be PL1 and PL1 under both the core and gpu column on the machine in limp mode, they're on nearly constantly.

On the working unit when under load they'll both be on but quite quickly go off after things calm down. What's strange regarding the faulty device, is, when rebooted limp mode will be gone, and I'm fully expecting it to perform closer to the working unit for a period of time, even directly after reboot.

I'll finish tests and get the screenshots posted soon.

Edit - the unit in limp mode has BD PROCHOT, VR THERMAL and VR CURRENT permanently on in yellow. The working unit doesn't even have them listed?

Edit 2....

So testing has finished, you can see the difference between the two sets of benchmarks with the runtimes.

Although both PL1's are red during testing with the 'normal' unit, they generally drop off after testing is finished, not the case with the limp device.

Max temp of the working unit has hit 104c floats between mid-60c to low 80c under load, the limp unit won't go anywhere near 90c max, and the pkg power is a max of 18.5w running the same tests as the working unit that hits 28.6w. Working unit gets up to acceptable boost speeds of 3.5Ghz plus, at its very best the limp unit hits 2Ghz, but can drop right down to 0.8Ghz albeit not during these specific tests.

BCPRODHOT, VR THERMAL and VR CURRENT have been consistently yellow on the limp unit, but not visible on the working unit. As I say, reboot will restore performance immediately for a period of hours to days, only for the situation to occur again, usually at the worst possible time.

Throttle stop isn't enabled, its just monitoring in both cases with TS Bench running. They're the 'same' processor, same factory spec, same os, patch, bios and driver set. sat in the same position and thermal environment.

"Working Unit"