1 Reply Latest reply on Oct 2, 2011 11:26 AM by Jeff11

    Heat Sink Fan Operation - i7-990X LGA1366




      I am building a system using the i7-990X LGA1366 processor. I know the processor can generate an incredible amount of heat, so I want to make sure I have everything properly set up before powering it up.


      I have searched through this site, as well as several other sites searching for information on cooling.


      In particular, I want to make sure the heat sink fan is oriented correctly over the CPU.


      An Intel video re system integration said to install the heat sink fan toward the front of the computer. That presents a  conflict with the computer case. I am using a Cool Master HAF X type case. The orientation of the motherboard is such that if I would try to orient the fan toward the front of the case, the heat sink thermal interface would not be oriented correctly. (The heat sink copper interface and the chip surface are more rectangular, so ideally, I would think the heat sink mating surface would be mounted somewhat similarly to the orientation of the CPU. I hope that makes some sense.)


      I have also searched in an attempt to determine the direction of airflow through the heat sink cooling fins. (I will be able to determine this once I power the system up; but, I'd like to make sure everything is right before powering the system up.)


      Is the fan mounted to the heat sink assembly "pushing" air through the fins of the heat exchanger, or is it pulling air. (Based on the fact there is no shroud, and the integration video I viewed said that the fan should be oriented toward the front of the computer case, I am thinking that this is probably a pusher type fan arrangement. Being that I understand most air flow would be from the front of the case to the rear, that would make sense having the fan mounted in that orientation on most systems.)


      This Cool Master case actually has 4 fans, plus the power supply fan. Two are supply and two are exhaust. There is a fan immediately above the CPU. It is exhaust, so it would make sense to have the fan/heat sink oriented so that the fan is below the heat sink (with the heat sink between the Intel CPU fan and the exhaust fan on the case).


      This makes pretty good sense as I write the information down. I hope to confirm that the fan on CPU is indeed pushing air (as opposed to pulling it).





        • 1. Re: Heat Sink Fan Operation - i7-990X LGA1366

          The vast majority of CPU heatsinks , including the standard Intel models, all use "push" fans, or more accurately the fans are oriented to push air over the heat sink.  The common "downdraft" or down-flow Intel CPU cooler, where the fan is above the heat sink fins and pushes air down through them, is also meant to cool the components surrounding the CPU, as the airflow spreads out onto the mother board.


          Intel also rarely supplies a CPU cooler that is somewhat similar to the typical "high-end" aftermarket CPU cooler, where the finned heatsink has it's fan mounted to move air across it, with the air flow parallel to the motherboard's surface, rather than down onto or perpendicular to the mother board.  The i7-990X is one of the few CPUs that Intel might include this type of CPU cooler with.  I am uncertain which of the two types I described you have, but I believe you have the downdraft type.


          Your confusion regarding mounting the heatsink fan towards the front of the computer, is caused by the integration video assuming the use of the unusual (for Intel), second type of CPU cooler I described.  Since that cooler moves air across the heatsink fins and the mother board from (for example) left to right, rather than down onto it, the airflow has a direction, such as, from the front of the case, towards the back.  The downdraft cooler has no single airflow direction after passing through the heatsink, and is diffused equally in all directions across the board.


          Traditionally, PC cases had few vents and fans, the only common one being the vent at the top rear of the case, and/or the top mounted power supply and it's fan.  So it makes sense, when using the unusual type of Intel CPU cooler, to mount the fan towards (a better term than near IMO) the front of the case, so that it pushes air toward the rear vent(s), where it is hopefully exhausted with the aid of another fan.  That is the purpose of that suggestion in the integration video, but is inapplicable to the downdraft type of CPU cooler, as you really know.


          You have a modern PC case, far superior to the old designs, and have many more options for removing heat from the case.  Use the fans you have, I recommend the two at the top as exhaust, the others as intake.  If you had a single-direction air flow CPU cooler, you could orient the fan to move air out the back or the top.  The downdraft type can still use the top exhaust style case air flow, since heat tends to rise.


          To much text to explain a simple concept, but does this make sense?