An update on the battle over Tj max.. worth reading

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GigaByte
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An update on the battle over Tj max.. worth reading

Post by GigaByte »

I thought I'd say so here, for the hell of it. Who knows maybe some changes to CoreTemp will follow.. I know I said I was done with this as the devloper is heart set on the current Tj max values but I can't resist so here goes..

A few of us may be aware of the Core 2 Duo and Quad temp guide @ TomsHardware here: http://www.tomshardware.com/forum/22174 ... ture-guide (Credits to Computronix!)

This guide has recently been updated to March 13, 2008 but you can only see it once you register and account there, and you need to wait for admin to validate it. If you view it while unregistered you will see the old Feb 25, 2008 version and it is NOT accurate. To make it easier for you I will post the important pieces:
Section 4: Thermal Flow

Heat originates within the Cores, where Tjunction sensors are located within the hot spots of each Core. Heat dissipates from the bottom of the Cores through the CPU Case, which creates a thermal gradient toward the center of the Die, where the Tcase sensor is located. Heat then dissipates through the socket and motherboard to air inside the computer case. Heat also dissipates from the top of the Cores through the Integrated Heat Spreader and CPU cooler to air inside the computer case. Safe and sustainable temperatures are determined by CPU cooling efficiency, computer case cooling efficiency, Ambient temperature, Vcore, clock speed and Load.


* Tjunction is always higher than Tcase.


* Tcase is always higher than Ambient.
(E) Many popular software utilities assume Tjunction Max can be as high as 105c, which results in high Core temperatures and high Tcase to Tjunction Delta. Empirical data instead shows that C2Q and C2D variants range from Tjunction Max 85c to 95c, which results in lower Core temperatures and lower Tcase to Tjunction Delta.

(F) Tjunction Max 85c to 95c is validated by Intel documentation which shows Tcase to Tjunction Delta is 5c at 100% Load.
Section 6: Scale

Safe and sustainable temperatures vary according to Spec#. The temperature Scales shown below illustrate the Delta between Idle and Load, and the typical 5c Delta between Tcase and Tjunction among C2Q / C2D variants. Although the Delta between Tcase and Tjunction is relatively consistent, temperatures do not always scale in a precisely linear manner with respect to one another, due to Variables such as Vcore, clock speed, Stepping and Load. Idle at very low Vcore and clock may cause Tcase to Tjunction Delta to indicate as low as 2c, while 100% Workload at very high Vcore and overclock may cause Tcase to Tjunction Delta to exceed 8c.

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.
Scale 1: Duo
E4x00: Tcase Max 73c, Stepping M0, TDP 65w
E2xx0: Tcase Max 73c, Stepping M0, TDP 65w
E8x00: Tcase Max 72c, Stepping C0, TDP 65w
E8x90: Tcase Max 72c, Stepping C0, TDP 65w
E6x50: Tcase Max 72c, Stepping G0, TDP 65w
E6540: Tcase Max 72c, Stepping G0, TDP 65w

-Tcase/Tjunction-
--70--/--75--75-- Hot
--65--/--70--70-- Warm
--60--/--65--65-- Safe
--25--/--30--30-- Cool

Scale 2: Quad
Q9x50: Tcase Max 71c, Stepping C1, TDP 95w
Q9300: Tcase Max 71c, Stepping M1, TDP 95w
Q6x00: Tcase Max 71c, Stepping G0, TDP 95w

-Tcase/Tjunction-
--70--/--75--75--75--75-- Hot
--65--/--70--70--70--70-- Warm
--60--/--65--65--65--65-- Safe
--25--/--30--30--30--30-- Cool

Scale 3: Quad
QX6x50: Tcase Max 65c, Stepping G0, TDP 130w
QX6800: Tcase Max 65c, Stepping G0, TDP 130w
QX6700: Tcase Max 65c, Stepping B3, TDP 130w
QX9650: Tcase Max 64c, Stepping C0, TDP 130w
QX9775: Tcase Max 63c, Stepping C0, TDP 150w

-Tcase/Tjunction-
--65--/--70--70--70--70-- Hot
--60--/--65--65--65--65-- Warm
--55--/--60--60--60--60-- Safe
--25--/--30--30--30--30-- Cool

Scale 4: Quad
Q6600: Tcase Max 62c, Stepping B3, TDP 105w

-Tcase/Tjunction-
--60--/--65--65--65--65-- Hot
--55--/--60--60--60--60-- Warm
--50--/--55--55--55--55-- Safe
--25--/--30--30--30--30-- Cool

Scale 5: Duo
E6x00: Tcase Max 61c, Stepping L2, TDP 65w
E4x00: Tcase Max 61c, Stepping L2, TDP 65w
E21x0: Tcase Max 61c, Stepping L2, TDP 65w
X6800: Tcase Max 60c, Stepping B2, TDP 75w
E6x00: Tcase Max 60c, Stepping B2, TDP 65w
E6x20: Tcase Max 60c, Stepping B2, TDP 65w

-Tcase/Tjunction-
--60--/--65--65-- Hot
--55--/--60--60-- Warm
--50--/--55--55-- Safe
--25--/--30--30-- Cool

Scale 6: Quad
QX6800: Tcase Max 55c, Stepping B3, TDP 130w

-Tcase/Tjunction-
--55--/--60--60--60--60-- Hot
--50--/--55--55--55--55-- Warm
--45--/--50--50--50--50-- Safe
--25--/--30--30--30--30-- Cool


Section 7: Parameters

(A) NO temperatures can be less than Ambient.

(B) Normal Ambient temperature is specified at 22c.

(C) Vcore Load should not exceed 1.4 volts on 45nm processors.

(D) Vcore Load should not exceed 1.5 volts on 65nm processors.

(E) All temperatures increase as Ambient, clock and Vcore increase.

(F) Tcase Idle is always higher than Ambient, even if less than 0.5c.

(G) Tjunction Idle average Core should typically be at least 2c higher than Tcase.

(H) Tcase to Tjunction Delta is typically 5c +/- 3c during Prime95 Small FFT`s.

(I) Tjunction Load should not exceed Hot Scale for the CPU being tested.

(J) Tcase Load should not exceed Hot Scale for the CPU being tested.

(K) Tjunction Idle and Load Results are average Core temperature.

(L) Idle to Load Delta may exceed 25c when overclocked.
Hopefully you understand the info from the quotes above. One thing people need to understand is Intel generates thermal spec on Tcase not core temps! Core temps are always higher than Tcase, so don't panic that your core temps look like they are above thermal spec because you are not. If you core temps are at 74c your Tcase is at 69c (+/-3c) as the delta is 5c (+/-3c). Still don't believe Tcase is what you watch for thermal spec? Click the Intel link for below, straight answer from Intel people!

http://processorfinder.intel.com/PopUpH ... hermalSpec

So now that you hopefully understand thermal spec is Tcase not core temps and that core temps are always higher than Tcase on IDLE and LOAD, and last but not least NO temp is lower than ambient lets get to the roots of this post.. Tj max.

The answer to Tj max is within Tcase max itself. Don't worry I thought the same thing as you all do right now after seeing I said that. I have not noticed it at all untill the updation of the temp guide on TomsHardware, then boom I saw it instantly. Lets use E2xxx/E4xxx L2 and M0 stepping as an example.

E2xxx/E4xxx L2 stepping has a Tcase max of 61c
E2xxx/E4xxx M0 stepping has a Tcase max of 73c

L2 stepping is believed to have a Tj max of 100c while M0 stepping is believed to have a Tj max of 85c. Well lets take a look at that, first using the common sense method. First of all the L2 stepping's Tcase max of 61c shows this stepping can't tolerate very much heat compared to others, so why on Earth would the Tj max be 100c? (Keep in mind Tj max = shutdown temp.) Thats very far ahead of the processor's maximum rated temp.

M0 stepping has a Tcase max of 73c, we all know this stepping can tolerate 12c more heat, thats quite a bit. Now if this stepping can tolerate more heat, why in the world would the Tj max be at 85c? Comparing these two that is saying the processor that CAN'T tolerate as much heat will shutdown from overheating at a temp 15c higher than the other stepping of the same processor which can tolerate 12c more heat before going over its rated spec? Does that make ANY sense? Plain and simple, NO.

Now lets compare these 2 processors using ever so basic math.. L2 stepping with it's Tcase max of 61c. So lets subtract Tcase max from it's proposed Tj max, you will be shocked.

100c - 61c = 39c - 5c (delta) = 34c (don't forget the 5c delta! Remember we are talking Tcase max and Tjunction max, as Tjunction is always 5c (+/-3c) above Tcase!) So L2 steppings have to go 34c above maximum rated spec in order to shut down? Seems a little much huh? I would say the thing would have already took damage..

Now M0 stepping with it's Tcase max of 73c. Again subtract Tcase max from the proposed Tj max. This one will shock you even more.

85c - 73c = 12c - 5c (delta) = 7c!! Holy.. so the stepping M0 which can take more heat that the L2 stepping while still within safe operating temps only has to go 7c above maximum spec to shut down??? Wow these can't take heat woth $^#%!! So then why don't I buy a L2 stepping?! Surely they take WAY more heat then! But wait.. Tcase max is higher on M0 stepping so.. err what the... *buzz* this is NOT correct... See what I mean?

So whats the Tj max then if these don't work? How about we flip them around, ie; 100c to M0 and 85c to L2? Guess what? That is also incorrect, partially, 85c for L2 stepping is CORRECT. The Tj max for M0 steppings is.. this will be new to many, but it is 95c. Yes 95c, in order to get the correct delta and thermal throttle temps, 95c fits perfectly. Lets redo the comparisions shall we?

Ok L2 stepping with its lower Tcase, clearly means it can't tolerate much heat right? Right. M0 on the other hand can go 12c before out of spec right? Right. That was simple. Now for some more basic math.. same as above, with the "new" Tj max. L2 first M0 second.

85c - 61c = 24c - 5c (delta) = 19c So L2 steppings core temps have to go 19c higher in order to shutdown, that seems much more within limits!

95c - 73c = 22c - 5c (delta) = 17c And M0 steppings core temps have to go 17c higher in order to shut down, this is more like it! Don't let the 2c difference confuse you, remember the 2 steppings have a 12c Tcase max difference between them while the cores have a 2c difference between them. So if you think about it for about 2 seconds you will notice the M0 clearly takes more heat by a fair ammount, just like Tcase shows.

With all of what I said, here is a list of what Tj max would be in the next version if CoreTemp was my program.

L2 Stepping: Tj max 85c
B2 Stepping: Tj max 85c
M0 Stepping: Tj max 95c
B3 Stepping: Tj max 95c
G0 Stepping: Tj max 95c
C0 Stepping: Tj max 95c
C1 Stepping: Tj max 95c
M1 Stepping: Tj max 95c

Yes Q6600 B3 stepping and QX6800 with B3 stepping are still Tj max 95c even though their Tcase max is lower. They need the 95c Tj max as giving them an 85c to "compensate" for lower Tcase max will make their temps INCORRECT as in Tcase higher than cores which is impossible, and remember what the guide said, and because it is correct, Tcase max is always your limiting temp, not the cores. You always hit Tcase max FIRST. If you choose to go beyond Tcase max you will be offically running your processor above Intel's thermal spec and only then the next limit will be PROCHOT# (thermal throttling) at 5c (+/-3c) before Tj max, then shutdown.

This is about it, all I can say now is please reconsider the current Tj max values used in CoreTemp as there is no 100c or 105c Tj max as of yet. As you know I cannot force you to make a change to your program no matter how much proof but I did my best in trying to get you to understand whats correct and whats not. The proof is there but all in the end its up to you. RealTemp is going down into a deep black hole with the next update as the devloper thinks 98% of the processors are all Tj max 85c and everytime I try to open disscussion with him he constantly insists his IR gun is the perferct fail proof way to magicaly find Tj max.. While speaking here I find it a little easier to try and explain such a thing, at least I don't get told the same sheer incorrect answer constantly.. so I figured I'd try to get at least one of the Intel Core temp monitoring softwares to display correctly.

EDIT: It appears that the devloper of RealTemp is even forcing 85c Tj max to quad cores and G0 steppings.. he pretty much put 85c Tj max for every existing CPU... oh well it was a good program at first :(

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Post by Vinas »

I agree with GigaByte.

Why not just put an adjustment for tjmax in options? Still keep the default values but also allow us to choose our own tjmax if desired.

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Post by The Coolest »

Will consider it.
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Post by Doodies »

At this point, I am pretty certain and many others have agreed upon that the tjmax for these M0 stepping cpus is 85c.


Gigabyte you were basing most of your argument on computronix old calibration guide which showed the tcase and tjunction were separated by 10-15c. According to his new guide it should be +/-1c at idle and up to 5c under load, which would make 100c or even 95c tjmax out of the question.


If you look through these you should find enough evidence to support the 85c tjmax.

http://www.overclock.net/intel-cpus/305 ... dts-8.html


http://www.overclock.net/intel-cpus/263 ... ronix.html
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Post by graysky »

The Coolest wrote:Will consider it.
Agreed, this is a must-have feature for CT in order to stay competitive with realtemp.
Version 2.2
March 13, 2008:
-changed TjMax from 95C to 85C for all M0 processors based on an IR temp reading.
-fixed the log file so it can be read correctly in NotePad or WordPad
-added a RealTemp.ini file to the archive that looks like this:

[RealTemp]
TjMax=0
IdleCalibration=0
LogFile=0

The TjMax tag lets you set an offset if you don't agree with the TjMax that RealTemp has selected for your processor. The choices are -3, -2, -1, 0, 1, 2, 3. Each choice provides 5C of adjustment, either positive or negative. If RealTemp says your TjMax=85C but you believe it is really 95C then you would use TjMax=2 in the .ini file to fix things up.

The IdleCalibration ranges from -2 to 2 and will be automatically saved when you close the program.

The LogFile can be set to either 0 or 1. LogFile=1 will turn the log file feature on and this too will be updated when you close the program.
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Post by cpmee »

L2 Stepping: Tj max 85c
B2 Stepping: Tj max 85c
M0 Stepping: Tj max 95c
B3 Stepping: Tj max 95c
G0 Stepping: Tj max 95c
C0 Stepping: Tj max 95c
C1 Stepping: Tj max 95c
M1 Stepping: Tj max 95c



Yep, when I was using RealTemp and it had a 95C Tj max for my M0 2180, the temperature world seemed to make logical sense again.

But then the author put it back to 100C.


IMO, based on the readings I was getting, 95C for M0 is the magic number.
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Post by Vinas »

I can't wait for this to be added. Real temp is ok but I'd really like to go back to core temp. Nobody I know uses core temp anymore because the readings are so far off for 45nm...

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Post by The Coolest »

It has been since 0.98. Check out the homepage
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Post by Vinas »

Sweet! Thanks for adding this!!! (downloading now) :lol:

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Post by Vinas »

Just thought I'd post back and say CT is working excellent for me now. The new logging capabilities put it over the top. EXCELLENT WORK!!!

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