Even after configuring Linux on a Lenovo ThinkPad T420s, the laptop can still experience unexplained CPU throttling that degrades performance. A common cause is an externally asserted BD PROCHOT (Bi-Directional Processor Hot). While standard PROCHOT is initiated internally by the processor when it overheats, BD-PROCHOT allows other components, such as power supply sensors or battery circuitry, to send a hardware signal directly to the CPU, which triggers processor throttling regardless of actual CPU core temperatures. What does BD-PROCHOT do to the Lenovo ThinkPad T420s? The CPU clock speed is locked at a low frequency, which causes severe system lag during … Continue reading →