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.
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.
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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