Microsoft’s Surface Pro 6 throttling at 0.4GHz after update na

Microsoft’s Surface Pro 6 users are complaining that their system’s CPU speed is stuck at 0.4GHz after a recent update. Microsoft acknowledges the problems and promises to come up with a fix soon.

A large number of Surface users are complaining on Reddit about what has become known as the ‘0.4GHz bug’. The most recent reports concern the Surface Pro 6, which appears to be experiencing severe throttling after an August 1 firmware update. While Microsoft reports on the page for that update that there are no known issues about it, the company confirms to Tech Republic that it has seen the complaints and plans to release a firmware update soon that fixes the issue.

However, the problems are not limited to the Surface Pro 6. Owners of the Surface Book 2 have been complaining about throttling to 0.4GHz since at least a year ago, but also six months ago. It concerns different users, but it is not known how widespread the problems are.

Users trace the problems to the cpu flag bd prochot and associated sensor on the motherboard. BD prochot stands for bi-directional processor hot. The idea is for processors to clock back when they reach a certain temperature to prevent overheating. Manufacturers can adjust the sensitivity of the sensor via firmware updates to set the degree of throttling and thus ensure longer battery life, for example.

Disabling bd prochot with a tool like ThrottleStop works for some, but doesn’t seem to work for every user. For other users, simply unplugging the Microsoft Dock, or doing a hard reset works, while for some, nothing seems to work.

You can read more about throttling in the background article Throttling of laptops, hence the variation in performance.