Surface Pro 6 in black
Unreliable update

Surface devices are throttling processor to 400MHz

Microsoft latest firmware update is causing Surface CPU to throttle down to 400MHz on some devices, and a fix is in the works.

Microsoft recently started rolling out its August 2019 firmware update for Surface devices, but it appears that it’s causing some throttling issues with Surface Book 2 and Surface Pro 6 devices.

According to a number of complaints on Reddit (link 1) (link 2), after installing the latest firmware, the devices are experiencing higher than normal thermal throttling causing the processor to drop its clock speed down to just 400MHz intermittently. This behavior happens when the Surface is plugged in to a power source or unplugged with battery fully charged.

It’s unclear the reason that’s causing this throttling problem, but it appears that it’s a driver issue. Some users believe that it has something to do with the bi-directional processor hot (DB PROCHOT) sensor settings, however, even disabling the feature didn’t appear to resolve the issue.

Other users suggested that installing the driver pack from Microsoft on their Surface Pro 6 and Surface Book 2 fixes the issue, but some people are revealing that installing the pack may lead to other problems.

Ultimately, resetting the device or reinstalling Windows 10 seem to be the only option to successfully mitigate the CPU throttling to 400MHz.

Although is bad news for Surface Pro 6 and Surface Book 2 owners, Microsoft has issued a statement to TechRepublic stating that it’s aware of the processor exhibiting slow performance, and it’s actively working to address the issue “via a firmware update.”

In addition to the processor throttling problem, the recent firmware update has also been causing problems with wireless connectivity on Surface Pro 6 and Surface Book devices. As reported in the Microsoft forums, after installing the update, which includes the new Marvel Wi-Fi driver, devices can no longer connect to the 5GHz Wi-Fi band. However, unlike the throttling issue, rolling back the wireless driver to the previous version using Device Manager seems to mitigate this particular issue.