BD PROCHOT – CPU running at 34% maximum frequency

BD PROCHOT thermal limiting CPUs detection, workaround, and real fix of a new motherboard

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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

System Information 
CPU 
Summary 
5331% 
Totals 
Handles 
125m 
3,447 
GPIJ 
Context Switch Delta 
Interrupt Delta 
Topology 
19 
13,322 
Shaw one graph per CPU

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”.

Resource Monitor 
File Monitor Help 
cpu - Total 
Overview CPU 
proc 
Image 
Memory Disk Net'.wrk 
20% CPU U 
6760 
8280 
11072 
16880 
9580 
17100 
10268 
3840 
34% Maximum Fre en 
Descripti„ 
Backgrom 
Win d cum 
Search 
Store 
Settings 
Calculat„ 
Microsom 
Video Am 
Status 
Suspenm 
Suspenm 
Suspenm 
Suspenm 
Suspenm 
Suspen_ 
Suspenm 
Suspen_ 
Suspen_ 
Threads 
CPU 
backgroundTaskHostexe 
ShelExperienceHostexe 
O secure system 
WnStoreAppexe 
MicrosoftMsnNewsexe 
60 Seconds 
Service CPU usage

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.

File Monitor Help 
Overview CPU Memory 
mage 
Disk Network 
17% cpu 
Descripti 
Status 
33% Maximum F 
Th reads 
cpu 
Ave rag „

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.

OL'mit Reasons 
core i5-6300HQ 
CORE 
RING 
EDP 01

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?

core i5-6300HQ 
VID 0.7241 V 
7.97 x 100.174 MHz 
798.39 MHz 
FID 
7.97 
7.97 
7.97 
7.97 
coc,'o 
71.2 
73.8 
65.2 
64.8 
CMod 
100.0 
100.0 
100.0 
100.0 
Chip 
100.0 
100.0 
100.0 
100.0 
Temp 
340C 
360C 
340C 
350C 
Max 
470 C 
490C 
490C 
480C
OL'mit Reasons 
core i5-6300HQ 
CORE 
RING 
EDP 01

CPU Details

MSR  0x1FC

BD PROCHOT Disabled

t RT MSR Tool 
EAX 
MSR Number OxlFC 
Core 
2 
3 
Copy To 
Write I 
w rte I 
Write I 
Write I 
Write MSA 
Read MSA

BD PROCHOT Enabled

tRT MSR Tool 
EDX [63.321 EAX (31.01 
MSR Number OxlFC 
Core 
2 
3 
Copy To 
Write I 
Write I 
Write I 
Write I 
Write MSR 
Read MSR

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?

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