The following article is about my digging into a performance issue.  It was only resolved with a hardware replacement.  The details below show troubleshooting, a method of detection, and a workaround.

My Dell Precision 5510 is running like a 486!!!

Machine is running super slow.  Sharing and running Hyper-V is unusable.   Task Manager (Ctrl+Shift+Esc) wasn’t showing anything useful.  It was showing 100% CPU utilization but this was on Windows 10.  Doing some more digging with sysinternals processmonitor I noticed the clock speed was fixed at 800mhz.

 Turns out my Intel i5-6300HQ CPU is running at only 800mhz!?!?!! 

CPU Details

http://ark.intel.com/products/88959/Intel-Core-i5-6300HQ-Processor-6M-Cache-up-to-3_20-GHz

Resource Monitor

Instead of using Sysinternals I remembered the native Windows application Resource Monitor and started using that after multiple reboots and BIOS updates (don’t forget to suspend Bitlocker before a BIOS update).  One of my favorite quotes is a scientist rarely says “EURKA! I have found it”.  Instead they say “Gee that’s funny”.

Maximum Frequency

33% is my maximum frequency?  What happened to Intel Burst/Turbo Mode?  Bingle!  Doing some serious digging looks like the CPU is going into thermal panic.  Thermal panic has an official term called BD PROCHOT.

BD PROCHOT

PROCHOT is not the same as BD PROCHOT

PROCHOT is about CPU thermal restriction.  The heat of the CPU is not high… so that isn’t why it is slow

BD = BiDirectional = Components on the motherboard are saying slow the CPU down so they can catch up.

Best writeup I found

From <https://linustechtips.com/main/topic/531278-skylake-system-stuck-at-800mhz/>

BD PROCHOT stands for bi-directional processor hot.  This allows other sensors on your motherboard to signal the CPU which forces the CPU to use the minimum multiplier (8).  The CPU behaves exactly the same as if it was thermal throttling but in this case, the CPU temperature is fine.  On some motherboards, it can be either a temperature switch from the voltage regulator or a power consumption switch.  On your motherboard, it is very likely that the Slow Mode switch intended for LN2 users is failing.  The only fix is a new board.  This problem has nothing to do with Windows.  

But what if you can’t (or won’t) replace the motherboard?

Workaround

https://www.techpowerup.com/download/techpowerup-throttlestop/

ThrottleStop is the only free software available that lets a user disable the BD PROCHOT signal path.  When you uncheck BD PROCHOT, that blocks signals from the defective switch getting to your CPU.  A simple fix and after you disable BD PROCHOT, you should be able to exit ThrottleStop and the BD PROCHOT signal path will remain disabled.  ThrottleStop also has an option that you can add to the INI configuration file.

Additional Info

What does a BD PROCHOT affected CPU look like?

CPU Details

MSR  0x1FC

BD PROCHOT Disabled

BD PROCHOT Enabled

Turns out this was a hardware failure.  This was instantly fixed by a warranty motherboard replacement by Dell.  I should have called in a ticket long before.

Detection method

Hmm there must be a method to see what the current CPU multiplier is or the EAX Number.  I didn’t have time to look it up.  Anyone know how to get this from command line, WMI, or something else?