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Old October 17, 2008, 10:18 AM
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3oh6 3oh6 is offline
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Join Date: Mar 2007
Location: Edmonton, AB
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Default I'll Take Cooling For A $1000 Alex



My biggest beef with motherboards these days is the completely inadequate cooling that these stock heat pipe solutions provide. Sure they give a company a chance to brand a board and wow the average Joe computer buyer with the flash, but they are terrible at what they are suppose to be doing...cooling the chipset. This is the stock cooling that comes with the EVGA 790i SLI FTW Digital PWM.

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The stock cooling on the 790i FTWD is very similar to the reference designed 790i Ultra but the fan works in a completely different fashion. On this board, the fan sucks air in from the CPU socket side and blows it out sideways to the rear of the case. This is a better solution to the reference design in my opinion, but the fact of the matter remains. The cooling is inadequate to maximize the motherboard and the integrated heat pipe mess, like every motherboard these days, makes it a pain in the ass to change. Not only do you have to cool the north bridge, but also the PWM area as well as the SB. Nothing like buying a $300+ motherboard and then another $50+ just to get decent cooling on the chipset so you can maximize the boards capabilities.

Like the 790i Ultra reference design, the heat pipe assembly does use screws exclusively which is better than pushpins. It is still a very weak compensation but better than the alternative I guess. The other thing I would like to touch on is the fact that a Thermalright Ultra-120 does fit in a front-to-back orientation, but as you can see in the second photo, it does touch the heat sink on the north bridge and requires some wrestling to get done. The other negative aspect of this board is again the inclusion of surface mount capacitors on the rear of the board. All large heat sinks and water blocks will use a back plate, if the user is not careful and provides a layer of something between the back plate and the board, those capacitors will get damaged. There were a number of experiences found in forums with people and mysteriously dead 790i Ultra motherboards...after using a back plate. This is un-acceptable from all manufacturers and I will continue to bytch about it until it is changed in future designs, which isn't going to happen so get use to hearing me harp on it :up:.

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Looking at the underside of the heat pipe assembly from the underside, we can see there are stand offs to protect the core and ample thermal paste has been applied. It was nice to again see a moist thermal paste applied as opposed to that hard crusty stuff some manufacturers use. At least with this thermal paste, should the board flex, there won't be a separation of the chipset and the paste that can't be re-created naturally. The PWM heat sink simply uses a thermal pad which is more than adequate for its purposes. The last two photos above are of the actual north bridge and south bridge dies. These are naked and exposed to the world when the stock heat pipe assembly comes off so care needs to be taken not to chip, crack these dies.

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The last set of photos is dedicated to showing alternative cooling options. For the digital PWM FETs, I found Swiftech MC14s to fit nicely between the back of the CPL inductors and the last row of surface mount capacitors at the back. It is a tight fit and you want to make sure the MC14s aren't touching anything else that could cause a short but they definitely fit. Another option would be Enzotech MOS-C1s. Next up was finding a solution for the north bridge and with the Noctua NC-U6, or any tower style north bridge cooler, the Thermalright Ultra-120 will not fit in a front to back orientation. I tried every angle possible but it just won't work, the only option is top to bottom orientation for the CPU cooler. The last piece to the puzzle is a south bridge solution that will still allow for SLI and that is the Thermalright HR-05-SLI. I have used this combination on the 790i Ultra with great success but with triple SLI, you need an alternative south bridge option.

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Above I have demonstrated that the HR-05-SLI works perfectly for an SLI setup, even with dual slot cards like the GTX 280 shown here. For triple SLI setups, you can simply use a low profile copper heat sink that mounts with pushpins. I have used a P5B-Dlx south bridge heat sink in the past that worked well, even without a fan. Enzotech also has a nice solution, the SLF-1.

The last couple photos above depict the Swiftech MCW30 on the north bridge and the entire setup for the majority of air testing except for the initial FSB and memory testing. As I will mention in the memory clocking sections, the stock cooling on the north bridge really hampered memory clocking. It was only after I went to water cooling was I able to get the memory frequencies up to where I was use to seeing them from the 790i Ultra. This next setup is for those that just don't play by the rules, and aparently some think I have been cheating with this board so far...well this next step in SPP cooling definitely won't help my cause.

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The photos are in a somehwat backwards order because I didn't take any during the setup so they are of the tear down. The first photo shows the insulation enclosing the phase change evaporator and as you can see from the perfectly centered circle impression in the insulation, the evap had perfect contact on the SPP...or so I think. The rest of the photos simply show the setup at various stages. Overall, the insulation was quite adequate and the system ran like a champ. Unfortunately, the results weren't quite what I was hoping for but even still, the board responded surprisingly well.

Last edited by 3oh6; November 4, 2008 at 10:21 PM.
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