Hi,

• Background on Issue 

I've had the Thinkpad X1 Yoga 2nd gen (product # 20JDCTO1WW; BIOS version N1NET46W 1.33) since it came out. It's running the latest build (non-targeted channel) of Windows 10 Pro with all Windows updates and all Lenovo System updates installed (through Lenovo Vantage app), as of this writing.

The laptop has only professional/scientific software installed and it's strictly used in a work setting in a climate-controlled office (i.e. no exposure to extreme heat/cold, humidity, dust, etc.) (scientific/professional software like statistic analysis software, Office, browsing company websites and other non-entertainment professional sites, etc.) and there have been no system registry modifications, no 3rd party driver installation, or anything outside of the normal functioning of the system. Windows has never been re-installed/reset from the factory-shipped condition, and I haven't even accessed the BIOS for the first time since it was purchased. There's > 250GB free from the 1 TB SSD, and RAM utilization never reaches > 50% even on the heaviest of workloads.

• Issue

Up to Win 10 OS build 1607 back in 2016-2017, everything was running well. After installing builds 1703 and then 1709, and still now after the 1809 update (updated a couple of months ago, but nothing changed with that update), when I connect the laptop to external monitors (either to one or two 27-inch, 60-Hz 2K monitors [AOC Q2781PQ] outputting at 2K resolution), either via HDMI cable or thunderbolt (outputting video through DisplayPort alternate mode), the OS suffers a massive performance drop. The frame rate drops , everything becomes really slow and sluggish, right-clicking the Windows taskbar takes about 3-5 seconds, the same when maximizing/minimizing/moving/resizing windows. Essentially the OS becomes almost unusable. When I disconnect one monitor and just leave the laptop screen + 1 monitor, performance improves a bit but not by much. 

The only thing I noticed is that during the old OS builds 1607, I could hear the CPU fan going harder and the %CPU utilization was always >50% during heavy use (CPU temps always kept at <60-70 Celcius even during heavy CPU% usage). However, now after the aforementioned updates, the %CPU utilization barely goes > 15% and the fans rarely kick in; the laptop also remains relatively cool compared to the previous 1607 build (at around 60 Celcius). It almost seems like there's a CPU throttle that's making the whole OS sluggish. 

Has anyone experienced this issue and has any ideas as to what could be going on?

Thanks!

Thanks so much for the reply! I googled the software and the closest think that came up is TPFanControl so I'll install that and give it a try. 

However, if you have a direct link to the specific version you're using in your 2nd gen Thinkpad X1 I'd appreciate it if you could send me the link.

To give an update in the issue, after updating to the 1803 and 1809 builds the issue went away completely when connecting my Thinkpad X1 yoga 2nd gen to two 2K monitros (1 via HDMI port and the other via TB3 port using DP Alt mode mode) (with 1080p laptop monitor still on, so total of 3 monitors).

However, since updating again to the 1903 build (which I postpoened for as long as I could but eventually Microsoft found a way to shove it down my throat as usual) a cuople of weeks ago the issue came back. 

The only solution I've found is to unplug the monitors, put the computer in hibernation, wake it up, re-connect the monitros, and the issue seems to go away for a short while (defiently comes back if I put the laptop to sleep but also happens randomly after a while).