Intel Thermal Throttling - Automatic?

[Maverick2002]

I was reading this discussion: http://www.tomshardware.com/fo...core-temperature-guide

... this quote in particular:

"Safe and sustainable temperatures vary according to Spec#. The temperature Scales shown below illustrate the Delta between Idle and Load, and the 5c Delta between Tcase and Tjunction. Although the 5c Delta is relatively consistent, Tcase and Tjunction tend to converge at Idle and diverge at Load due to Variables such as Vcore and CPU cooler efficiency. Low Vcore and clock may cause Tcase to Tjunction Delta to indicate as low as 3c at Idle, while high Vcore and overclock may cause the Delta to reach 7c at Load.

If temperatures increase beyond Hot Scale, then ~ 5c below Tjunction Max, Throttling is activated. The Digital Thermal Sensors (DTS) are used to trigger Intel`s TM1 and TM2 technologies for frequency, multiplier and Vcore Throttling within individual Cores. If Core temperatures increase further to Tjunction Max, then Shutdown occurs. Since Tcase indicates CPU Die temperature only, it is not used for Throttle or Shutdown activation, however, as Tcase Max will be exceeded before Tjunction Max is reached, Tcase Max is always the limiting thermal specification."



... for purposes of setting up some things on work computers, and what I get from it is that Thermal Throttling is automatically activated on Intel processors, even if you disable it in the BIOS as a meltdown-prevention measure. Is this correct?

 

[rge]

According to intel, throttling occurs when DTS=0 (tjmax is reached), though software may indicate a few degrees before DTS=0 due to differences in sampling time between software reporting temp and temp being reached. My E8400 throttles at exactly DTS=0 (95C casing temp by Fluke) if DTS is approached slowly, my E6850 throttles at DTS=0 (95C casing temp).

Quote from intel specs http://download.intel.com/design/pro...s/31873201.pdf
"An external signal, PROCHOT# (processor hot), is asserted when the processor core temperature has reached its maximum operating temperature. If the Thermal Monitor
is enabled, the TCC will be active when PROCHOT# is asserted....The TCC causes the processor to adjust its operating frequency (via the bus multiplier) and input voltage (via the VID signals). This combination of reduced frequency and VID results in a reduction to the processor power consumption."

According to intel shutdown does not occur until tjmax is exceeded by 20 to 25C, ie around 120C. My E8400 shutdown at ~118C casing temp, my E6850 near same point slightly over 115C.

http://download.intel.com/design/pro...x/31873401.pdf
"In the event of a catastrophic cooling failure, the processor will automatically shut down when the silicon temperature has exceeded the TCC activation temperature by approximately 20 to 25 °C. At this point the system bus signal THERMTRIP# goes active and power must be removed from the processor."

Another quote from intel
"PROCHOT# is designed to assert at or a few degrees higher than maximum TCASE (as
specified by the thermal profile) when dissipating TDP power, and can not be
interpreted as an indication of processor case temperature. This temperature delta
accounts for processor package, lifetime, and manufacturing variations and attempts to
ensure the Thermal Control Circuit is not activated below maximum TCASE when
dissipating TDP power. There is no defined or fixed correlation between the PROCHOT#
assertion temperature and the case temperature"

That simply means, if your using intel cooler, and you are at full TDP power, if measuring tcase (casing cpu) with a thermocouple, tcase max (example 72C) should be reached right when tjmax is reached, ie 95C), and throttling should occur at or near tcase max, thus keeping your cpu in specs and protecting itself. But they go on to say this is not guaranteed as this gradient of ~20C at full TDP from core to casing is dependent on many variables...ie they are not responsible if you exceed tcase max and shorten life of your cpu, without it throttling. (Note this gradient is based on casing temps at full TDP, and not your cpu temp, which is between the cores where thermal conductance is still way above 100w/M-K, and the only gradient you will see there is ~5C. TIM1 (between core and IHS) has a thermal conductance 20x lower, and that is where the gradient occurs on high TDP.

EIST does not function on the cpu if you turn it off in the bios. So it is possible the thermal shutdown would not work if you disabled that in the bios...personally I have not tried to know for sure.

 

[Foxery]

I can vouch that this happened to me recently, when I botched a cooler installation. My core temperatures went right up to ~105C, and two out of four cores dropped their multiplier down to the "power saving" level. However, my motherboard was set to shut down long before this level, and it did NOT do so. I would love to know why.

Amazingly, the CPU still works.

 

[eelw]

Well I know throttling works on my E6400. Bored and decided to see how durable the chip was, removed the HSF. Ran the chip at full load for 30 minutes. Reached max temp very quickly, but stayed at 85C and didn't budge above it. Posting from said machine right now. Haven't tried the same test on my Q6600 yet.

 

[VirtualLarry]

Originally posted by: Maverick2002
... for purposes of setting up some things on work computers, and what I get from it is that Thermal Throttling is automatically activated on Intel processors, even if you disable it in the BIOS as a meltdown-prevention measure. Is this correct?

No, if you disable thermal management support in the BIOS, it is in fact disabled.

 

[VirtualLarry]

Originally posted by: rge
According to intel shutdown does not occur until tjmax is exceeded by 20 to 25C, ie around 120C. My E8400 shutdown at ~118C casing temp, my E6850 near same point slightly over 115C.

Well, that shoots down the theory that the solder melts at 73C. Thank you for proving my point (from another thread).