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05-05-2015 10:29 AM
I have a question:
Not too long ago I put on the 3.87 Rev A Bios update that was rated as a critical update on my Z420 Workstation (running Windows 7 Pro 64-bit), and lately I've found that the CPU is running about 20 degrees hotter than it used to at idle. I used to hear squeaky noises coming from the computer which I learned normally come from the power delivery circuits on the motherboard, but as long as I was hearing those the CPU would average around 50 degrees C at idle. I don't hear those noises anymore and now the CPU is average around 70 - 75 degrees C at idle. Not sure what the connection is. The HP Performance Advisor is telling me I am within normal range, but I just want to make sure that with programs like Autodesk Maya on there, it doesn't get too hot and shut the machine down. I don't know what the upper temp range is considered the maximum for safety. Could this change have been due to the Bios update?
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05-06-2015 01:55 PM
Update: The last couple of times I checked my CPU has cooled down for some reason back in the more normal range of 50 - 55 degrees C, and this is while I was using Autodesk Maya. Maybe its getting hot earlier was a fluke of some kind or maybe some sort of normal system processes running in the background running time to time got it pumped up. I'll keep monitoring.
05-06-2015 05:05 PM
There is a large variation in the maximum allowable CPU core temperature. It depends on the number of cores, frequency, and the particular version of CPU. Intel specifies a maximum junction temperature, Tj Max, for each CPU. I have seen Tj max variations from 85 deg. C to 105 deg. C.
Core Temp version 1.0 RC6 is a program that shows the core temps and also Tj Max. For some CPUs, this program shows the power being dissipated in the CPU and operating frequency. As long as the core temperatures are below Tj Max, the system is OK. Core Temp can show absolute core temperature values, or the distance from the core temp to Tj Max (Options -> Settings -> Advanced then check "Display the distance to TjMax in temperature fields).
In testing, I have run systems with 100% CPU usage on all cores, and rarely does the core temperature go to less then 10 degrees below Tj Max, even when running at 100% for weeks.
Did you remove the heatsink from the CPU? If you do, make sure you clean off the old thermal paste from both the CPU and heatsink, and use new thermal paste. Intel always recommends this, but I did not always follow their recommendations, until I tested some CPUs at 100% and noticed that some cores were almost at Tj max after I ran the tests again(!). The same system ran at least 10 deg. C below Tj max before I removed the heatsink. Replacing the thermal paste then brought the temps back to normal. FYI.
The Z420 BIOS has a setting to change idle power. Go into the F10 setup, under Power -> OS Power Management -> Idle Power Savings. There are settings for Extended (lower CPU idle power - should be on by default) or Normal. Selecting Extended will reduce idle power and drop idle CPU temps by several degrees, but might cause some of the noise you heard from the onboard voltage regulators.
As an aside, Workstation Xeon CPUs are designed to run hotter than what some expect. Higher frequencies run hotter and higher core counts run hotter - higher system performance in general causes higher temperatures. Intel tells us that CPU performance is limited by their thermals, so there is a tradeoff between power, cores, and performance.
I know many like to have lots of margin between Tj max and their CPU temperatures. But think of a car engine - it has more power when run closer to redline, but it runs a lot hotter. A cool CPU is usually not doing much, or is purposely designed to run at low power, like slow speed, low core count laptop CPUs that run on batteries. Intel CPUs will thermally throttle frequencies or shut down if they run too hot. As long as your Tj max is not exceeded under 100% CPU usage, don't worry about harming your system.
My opinions are my own, and do not express those of HP.
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05-09-2015 06:15 PM
Thanks for your response and suggestions. I did verify that in my BIOS settings the Power Management was set to Extended mode, but the temperature still hovered around 70 - 78 degrees at idle. I checked Intel's spec for this CPU (E5-1650 6-core xeon running at 3.2 Ghz per core) and although it didn't say anything about TMax, it did mention that the TCase (what it defines as the maximum temperature allowed at the processor Integrated Heat Spreader (IHS)) was 64 degrees Celsius. Now my case temperature, according to my HP Performance Advisor version 1.7.7517.0, is only about 24 degrees C, but I set my CPU fan speed a little higher, about 2009 rpm. It does make a little more noise, but my CPU temp has dropped to about 49 degrees. Before the change the fan speed was just over 1300 rpm although the Advisor was still telling me it was in "normal" range. Is it okay to bump up the CPU fan speed like this or should I go a little lower?
05-11-2015 04:22 PM
I am considering this resolved. I did go a little lower on the fan speed and the CPU temp is fine. But I still think the latest BIOS update did something to the way the power delivery circuits work, because even with the power management set to 'Extended' in the BIOS settings, I stopped hearing the little 'squeaky' noises that they make and the CPU temp shot up.