A mysterious CPU acceleration problem seems to be affecting selected Surface devices such as Surface Pro 6 and Surface Book 2. A TechRepublic report today explains that affected users see that their CPU is accelerated to 400MHz, and may have a more likely to encounter this problem if you have installed recent firmware updates.
Many users have complained about this acceleration problem in Reddit, and it seems that the cause could be Intel's BD PROCHOT (hot bidirectional processor) function that can automatically accelerate CPU to lower the overall temperature of a device. Intel's BD PROCHOT function is not exclusive to Surface devices, and is really useful for preventing PCs from being damaged due to overheating. However, users who disabled BD PROCHOT using a third-party utility called ThrottleStop have been able to solve the problem, as the Reddit user schmak01 explains:
It is the BDPROCHOT sensor. Install the choke. You will notice as soon as it reaches 400 mhz that the BDPROCHOT will go crazy. I think MSFT put a BIOS update that makes the sensor also sensitive. Acceleration is triggered too soon. This was probably done because people complained about the battery. You can use throttlestop to disable the acceleration of your processor. I have configured mine that way for about a year without problems.
Microsoft confirmed the problem of CPU acceleration on Surface Book devices in a statement to TechRepublic. "We are aware that some customers report a scenario with their Surface Books where CPU speeds are reduced," said the Microsoft spokesman. "We are working quickly to address through a firmware update," he added, without giving a specific ETA.
Additional readings: Intel, Surface, Surface Book 2, Surface Pro 6