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Introduced in March 2009, The Mac Pro (Early 2009) introduced Intel's Nehalem architecture to Apple's professional desktop line and introduced a subtle redesigned interior that remained through the 2010 and 2012 CPU updates.

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Looking for special fan to improve cooling of NBridge chip Mac Pro 5,1

Can you help me find a suitable fan?

I need a fan for the Northbridge heatsink in a Mac Pro 5,1. Do you know of a source for a suitable fan? Alternatively, do you know of any other solution to the problem. The problem is explained in detail in this post, below.

Incidentally, every owner of a Mac Pro (any of 4,1 and 5,1 models) should take steps to prevent their machines from frying themselves, as I explain below. Read on...

Planned Obsolescence in the Mac Pro 5,1

Overheating of the Northbridge chip on the Mac Pro 5,1 is an endemic problem in these machines. Failure of this chip is responsible for most main board failures. The plastic clips holding the heat-sink down are prone to deteriorate (lifetime of about 5 years) resulting in separation of the heat-sink, rapid overheating of the Northbridge chip and failure. It seems to be planned obsolescence.

Northbridge Heatsink on CPU Board

The image, below, shows the Northbridge Heatsink, visible after the CPU heatsinks have been removed. The image, taken from the Internet, shows one of the clips missing and plenty of dust on the heatsink. Make sure to regularly clean the dust from your machines; its presence reduces the efficiency of heat dissipation from heatsinks and directly from components. Mine is clean and both clips are in good order. Replacement clips can be found from various suppliers on Internet.

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This design fault (from the point of view of the user) can be repaired by replacing the clips with suitable metal bolts fitted with spring-loader washers, or regularly replacing them with standard plastic clips. Regular servicing should include cleaning the occluding chip & heatsink surfaces and applying new thermal paste before refixing the heat-sink. Every Mac Pro 4,1 and 5,1 owner should do this, or have it done with the regular service. However, the Northbridge still gets hot quickly, and races up to 80 degrees Centigrade and higher when the system is under load. I have seen reports of the Northbridge running above 120 C without failing, but we can be pretty sure that this is not a sustainable condition. The cooler you can keep your machine the longer it will last. Macs Fan Control makes it possible to keep the Northbridge cool by linking the Intake and Exhaust fans to ambient temperature and setting the maximum at 40 degrees Centigrade.

Macs Fan Control

The Macs Fan Control is a highly recommended utility. Proper use of this utility will extend the life of your Mac Pro for many years. The screenshot below shows the application interface. In the panel on the left are the fans and user settings. In the panel on the right are the sensors and readings in real real time. With judicious juggling and readjustment of the setting I have found a working solution to the problem desribed above. Below are my recommended settings.

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Recommended Settings

Never set fixed fan speeds. These may be wasteful if set too high, and may cause your computer to fry itself if set too low. The Auto settings adjusts fan speed according to real time temperature measurements.

PCI (Fan for PCIe bus) Use Auto setting and base the speed on PCIe Ambient temperature. Set the fan to start at 20 C., and to run at maximum at 40 C.

PS (Fan in power supply case) Use Auto setting and base the speed on PSM1 temperature for Supply 1. Set the fan to start at 30 C., and to run at maximum at 40 C. This tends to be a noisy fan.

EXHAUST (Fan at the rear of machine) Use Auto setting and base the speed Ambient temperature for main case. Set the fan to start at 30 C., and to run at maximum at 40 C.

INTAKE (Fan at the front of the machine) Use Auto setting and base the speed Ambient temperature for main case. Set the fan to start at 20 C., and to run at maximum at 40 C. The lower starting temperature of the intake fan ensures that there will be a slight positive pressure inside the computer case. This is helpful for keeping dust out of the machine.

BOOST A (Heatsink fan of CPU 1) Use Auto setting and base the speed CPU A Diode temperature. Set the fan to start at 25 C., and to run at maximum at 55 C.

BOOST B (Heatsink fan of CPU 2) Use Auto setting and base the speed CPU B Diode temperature. Set the fan to start at 25 C., and to run at maximum at 55 C.

The Problem with Fan Overdrive

This works but causes these large fans to run hard, keeping everything cool. This overkill solution takes more power than necessary and is noisy. I measure 60 to 70 dB at one meter from the tower as it ramps up, and above 80 dB when the computer is at full load. Incidentally, one hour of exposure to 80 dB is associated with permanent hearing damage. Since my tower is on a desk one meter from where I sit this noise level is unacceptable. Furthermore, it is unnecessary; only one chip overheats. The heat-sink is clearly inadequate. A larger heat-sink will not fit, as it is partly positioned under one of the main CPU heat-sinks.

An Improved Remedy

An improved remedy would be a small ancillary fan available that can be placed on the exposed part of the Northbridge heat-sink. This could take power from one of the unused power slots associated with the PCIe bus.

I have not been able to source such a fan. Does anyone know from where such a suitable fan can it be obtained? I hope to hear from someone more knowledgable than I.

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@baronbar - Great answer but you first need a question! This would be useful in a guide. I would encourage you to copy it over and post it there.

Sadly we'll need to delete it here as its not a question.


Hello Dan,

I asked a question at the end of this post. However, I have now created an introductory paragraph that starts with the question. Presumably this is what you want.

However, you may be interested in an FAQ type question, such as: How do I keep my Mac Pro ( any of 4,1 and 5,1 models) from overheating?


@baronbar - I think you missed the point ;-} One asks question's when they don't know the answer in 'Answers' so others might be able to help them.

If you know something you want to offer up as far as 'knowledge' thats were the guides come into play! I encourage you to create one with this info!

Here's the start point: it will walk you though it doesn't need to be big and you might even find creating a PDF file that is attached offers a bit more freedom.

Go for it!


I will do that when I have time. I will also make a video of the cleaning process, degreasing of the chip, replacemnt of thermal paste on CPU & Northbridge (perhaps also Southbridge) and installation of the Mac Fans Control. All in good time. In the meanwhile I am hoping someone can source a suitable fan for me.


@baronbar did you find a solution ?

I am about to upgrade my CPU's and my NB / NB Heat sink has a 10ºC Differential so I was keen to see what you experience was in finding a better solution than duct tape diverter

I also found this nice guide


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hello Baron

i am so surprised coz u did describe the problem and the steps that i did , i do have the same problem temperature rise up to 80 on idle , i did check the heatsink both clips are ok so i did ordered a Blower Fan from amazon and it was a bit loud and vibrate , so i got a 5v laptop fan from a local repair shop and connect it with usb cable it work and cooled the northbridge to 50 c .

the picture below my first try

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i just found a USB fan on amazon maybe help someone


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Hello, I have the same heating problem of the NB, the most feasible solution that I see, is to polish the lower part of the heatsink, it has very bad termination, that's why it does not refrigerate properly, that's why there are many degrees of difference between the Diode and the HeadSink.

As soon as I have the right tools to polish it, I will.

I'm sorry for my English.

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What do you mean by polish it? I think you only need to clean the old paste and replace it with new paste once a year when you do your general service.


I agree you don't need to polish it! Proper cleaning of the old thermal paste and applying a good quality paste is the key part! Thermal paste is designed to fill the micro pores of the both surfaces the chip & the heat sink to make the heat transmission better.

Its also possible your board needs a bit of TLC as its possible its developed a few cold solder joints which are adding load (resistance) and the caps may need replacing as they do wear out over time.

The real issue here is the North Bridge chip being used in this system is quite an old design whereas todays chips are much better so they don't heat up to the same degree.

I do think Baron's direction on replacing the heat sink with one with a fan would improve the cooling.


Did ya'll see where Segundo apologized for his English? I'm sure he did not means polish.


@mayer - Você quer dizer que o inglês dele é um pouco áspero


@danj Só precisa de um pouco de polimento


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Baron Bar zal eeuwig dankbaar zijn.

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