I remember when one of my friends got a 400MHz CPU just over 20 years ago. Owners of Microsoft’s Surface Books and Surface Pro products don’t have to remember back that far, though, because they’re seeing it right now. Microsoft has acknowledged a throttling problem happening on its Surface products that seems to persist across reboots.

Eagle-eyed sleuths on Reddit have narrowed the problem down to an Intel CPU flag, BD PROCHOT. That’s short for “bi-directional processor hot.” The flag can trigger processor throttling to help the system maintain a safe operating temperature. A variety of components can trigger the flag. With this current glitch, BD PROCHOT is activating even when CPU temperatures are low, and then it’s staying activated.

This flag isn’t just on Surface products; motherboards and systems from companies like MSI and EVGA have seen cases, too, but not to this scale. A recent Surface firmware update seems to have caused a spike on Microsoft’s products in particular.

“We are aware of some customers reporting a scenario with where CPU speeds are slowed,” Microsoft told TechRepublic via a spokesperson. “We are quickly working to address via a firmware update.”

TechRepublic notes that the third-party utility ThrottleStop, which intercepts the BD PROCHOT command, is helping users affected by the issue, and that if the computer is actually in danger of overheating, it’ll simply shut down.

Trouble under the surface

While Surface devices are generally well-liked among reviewers and definitely have a fanbase, the line is no stranger to trouble. At one point, Consumer Reports stopped recommending the devices because so many users had trouble with them. Surface devices have had issues with batteries draining, overheating power cords, and flickering displays. For some users, this might be the latest in a string of frustrating issues.

The firmware fix for throttling on the Surface is likely not far out now that Microsoft has acknowledged it. If BD PROCHOT is giving you a headache right now, though, ThrottleStop might be the only way to keep your Surface out of the computing stone age (for now).