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MP 1,1-5,1 CPU A runs hotter then CPU B

MrRedfield

macrumors member
Original poster
Jul 8, 2019
30
4
Hello,
I just upgraded my processors to dual Xeon X5690's. It seems that CPU A is running about 10 degrees hotter than CPU B. Is this normal? Sadly, I never looked at the temps before upgrading the CPUs.

Thanks!

BTW. My system is a 5,1

 

tsialex

macrumors G3
Jun 13, 2016
8,356
8,867
It's normal. CPU B gets the cooler outside air, CPU A gets the already warmed air from CPU B. Most people delta is around 6ºC or 7ºC, but there are some reports of 4ºC to 11ºC.
 
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chrfr

macrumors G4
Jul 11, 2009
10,185
3,897
my 12 core 2.66 is sitting here with about an 8ºC difference between the two. It's totally normal.
 
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MIKX

macrumors 68000
Dec 16, 2004
1,786
662
Aussie in Japan
My 4,1>5,1 has a 5°C difference. Normal.
It would seem that increasing Exhaust fan speed might reduce the difference slightly.


Off topic :
I would love to learn how to wire up new Noctua Intake & Exhaust fans original Apple cables to work with Apple thermal sensing.

Possible ? All ideas more than welcome !

I have already bought ( for my PSU ) a Noctua 120MMx120 NF-A12x25 fan kit
NF-A12x25 PSU 120mm fan kit.png


. . . .along with the Noctua NA-FX1 fan controller fan kit
Noctua Fan controller NA-FC1.jpg


- I have both a passive thermal sensor along with a Laser Thermal gun to monitor PSU temps so I don't need Apple Thermal monitoring. Anything under 40°C for the PSU in summer will please me.
 
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startergo

macrumors 68030
Sep 20, 2018
2,710
1,148
This is normal. What is not normal is CPU B hotter than A. Which I have seen in the thread where people try redirecting the fan flow towards the Northbridge diode.
 
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Alex Sanders74

macrumors 6502
Nov 26, 2013
272
61
Toronto, Canada
My 4,1>5,1 has a 5°C difference. Normal.
It would seem that increasing Exhaust fan speed might reduce the difference slightly.


Off topic :
I would love to learn how to wire up new Noctua Intake & Exhaust fans original Apple cables to work with Apple thermal sensing.

Possible ? All ideas more than welcome !

I have already bought ( for my PSU ) a Noctua 120MMx120 NF-A12x25 fan kit
View attachment 848879

. . . .along with the Noctua NA-FX1 fan controller fan kit
View attachment 848880

- I have both a passive thermal sensor along with a Laser Thermal gun to monitor PSU temps so I don't need Apple Thermal monitoring. Anything under 40°C for the PSU in summer will please me.

Very curious how this works out for you. These kits are really nice and have been looking at them for a while now....
 
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MIKX

macrumors 68000
Dec 16, 2004
1,786
662
Aussie in Japan
This is normal. What is not normal is CPU B hotter than A. Which I have seen in the thread where people try redirecting the fan flow towards the Northbridge diode.

EDITED :
As it stands, the Intake fan & Booster A fan direct airflow to the 4 front RAM slots and seeing that the Northbridge is basically (EDIT) almost under CPU A then diverting said airflow to the Northbridge ' should ' give extra cooling to both the NB AND CPU A.

Last April I tried the ' airflow diversion panel ' technique but the results were minimal, disappointing.

Instead, I installed USB fans to address the Northbridge chip and it stays at around ( EDIT ) 55 ~ 58°C / around 136°F if ambient temp doesn't go over 35°C / 95°F. Admittedly my Intake & Exhaust fan speeds have been set a bit higher in summer.

I also have a 16.4 CFM USB fan installed for the CPU A's front, four RAM slots, so I've got that covered for extra airflow.
 
Last edited:
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MIKX

macrumors 68000
Dec 16, 2004
1,786
662
Aussie in Japan
Very curious how this works out for you. These kits are really nice and have been looking at them for a while now....
Bear in mind that my main plan is to use a Noctua PSU fan without Apple thermal control but as I posted before, I can easily monitor and control that.

I'm going to contact Noctua regarding pinouts for their 80mm fans for the CPU Tray ( Intake & Exhaust ) to make them Apple thermal control compliant. It's all about the cable pinouts ( hopefully ).

Seeing that there are still literally millions of working, aging cMPs out there it could be good for Noctua to come up with a "Mac Pro Noctua fan adaptor cable kit". It is certainly worth considering and their fans are excellent and well crafted.

NOTE : The 4,1 & 5,1 's PSU fan cable runs UNDER the motherboard= a time consuming pain in the arse to remove.
example :
 
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Alex Sanders74

macrumors 6502
Nov 26, 2013
272
61
Toronto, Canada
Bear in mind that my main plan is to use a Noctua PSU fan without Apple thermal control but as I posted before, I can easily monitor and control that.

I'm going to contact Noctua regarding pinouts for their 80mm fans for the CPU Tray ( Intake & Exhaust ) to make them Apple thermal control compliant. It's all about the cable pinouts ( hopefully ).

Seeing that there are still literally millions of working, aging cMPs out there it could be good for Noctua to come up with a "Mac Pro Noctua fan adaptor cable kit". It is certainly worth considering and their fans are excellent and well crafted.

NOTE : The 4,1 & 5,1 's PSU fan cable runs UNDER the motherboard= a time consuming pain in the arse to remove.
example :

The thermal control aspect is what's deterred me from going further. Cable routing does sound like a royal pain... I'll keep my eyes open for what developments you discover on this front. Time and money are something I don't have a lot of to invest in this area right now. Appreciate your efforts!
 
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tsialex

macrumors G3
Jun 13, 2016
8,356
8,867
The thermal control aspect is what's deterred me from going further. Cable routing does sound like a royal pain... I'll keep my eyes open for what developments you discover on this front. Time and money are something I don't have a lot of to invest in this area right now. Appreciate your efforts!
Mac Pro fan RPM measuring is completely different than what PC fans use and the signals are not compatible at all.

If you connect an oscilloscope at the sense pin you will see that you can't replace a Mac Pro fan and make the SMC read the RPM of the PC PWM fan. Years ago a user here, sorry I don't remember who see edit below, did all the investigation needed and posted all the signal differences. You would need a micro controller to do the translation from one to the other. At the time seemed doable, but if no one did it already…

You can use the +12V and ground from the Mac Pro connections, but you can't use the management.

Edit: this post have more info about the difference between Delta fans used in the Mac Pro and common PWM PC fans:

https://forums.macrumors.com/threads/quieter-case-fans.1115475/#post-12708222
 
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MIKX

macrumors 68000
Dec 16, 2004
1,786
662
Aussie in Japan
That Austrian ? guy's video is spot on - he is truly bi-lingual but I cringed when he picked up the CPU Tray by the heatsink ! Definitely a NO NO with 4,1 & 5,1's trays.

CPU Tray by HAND.png


At the moment, in my De-dusting & cooling the Northbridge epic, https://forums.macrumors.com/thread...mp-reduction-in-dual-cpu-cmp-4-1-5-1.2179729/ the PSU temps are the only thing that concerns me, especially as I'm in humid, fiercely hot Japan. Yet due to Climate Change JP's Summer has been peaking about two weeks earlier since I first arrived here in 1994.

I'll report any developments re: CPU Tray area Intake & Exhaust fans.
 
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Alex Sanders74

macrumors 6502
Nov 26, 2013
272
61
Toronto, Canada
That Austrian ? guy's video is spot on - he is truly bi-lingual but I cringed when he picked up the CPU Tray by the heatsink ! Definitely a NO NO with 4,1 & 5,1's trays.

View attachment 849001

At the moment, in my De-dusting & cooling the Northbridge epic, https://forums.macrumors.com/thread...mp-reduction-in-dual-cpu-cmp-4-1-5-1.2179729/ the PSU temps are the only thing that concerns me, especially as I'm in humid, fiercely hot Japan. Yet due to Climate Change JP's Summer has been peaking about two weeks earlier since I first arrived here in 1994.

I'll report any developments re: CPU Tray area Intake & Exhaust fans.

That heatsink makes a great carry handle! :eek:
 
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