Is 10mm from VGA card enough room for fans to draw in air?

[Scott J]

I'm working on a video card heatsink/fan problem, where two 5850s are run in crossfire, each with its own aftermarket heatsink and fans. The PCI-E slot spacing on the EVGA Classified motherboard makes it possible, but it's still going to be a tight/cramped fit. If my measurements are correct, a 25mm deep fan (120x120x25mm) will leave just slightly less than 10mm of space between the intake side of the fans (on the heatsink for the first video card in PCI-e slot 1) and the back side of the next video card in PCI-e slot 3.

Before I make this any more complicated than it might need to be (i.e., slim 120x20 or 120x12 fans), is roughly 10mm (.39") enough "space" for regular size 120x120x25mm fans on the first VGA heatsink to get adequate air intake for cooling?

[MikeC]

It sounds really tight.

You could mount the fan/s blowing down towards the motherboard; straddling the two cards. If you have a side panel intake vent next to the video cards, this might work well.

Kind of like this solution from an article I wrote an eternity ago (by web years).
http://www.silentpcreview.com/article14-page5.html
See the bottom pic.

[Scott J]

Hi Mike, thanks very much for the reply.

It sounds really tight.

In my favor (from an airflow/thermal standpoint), I am using the new Silverstone FT02 case which has three 180mm bottom case fans blowing upward, and the MB is rotated 90° so the video cards hang down lengthwise from the case 'ceiling'. This should provide some positive cool airflow to the VGA heatsink fan intake, straight up the 10mm (.39") gap between the fans and the back of the next video card in PCI-e slot 3, but I don't know if it would be enough.

You could mount the fan/s blowing down towards the motherboard; straddling the two cards. If you have a side panel intake vent next to the video cards, this might work well.

No side panel intake, just a window panel, but if necessary, I think your solution will work. I measured the distances, and if a 120x120x25mm fan was mounted across the edges of the video cards, a 1/2" above the video cards blowing down toward the MB, it would leave about 1.0" of space to draw air between the fan and the case wall (or window, in this instance). If I understand correctly, one of the fan mounting options for the Prolimatech MK-13 is designed to work in a similar configuration as you described.

I would like to try to make the 'standard' method of mounting the fans directly to the width of the VGA heatsink work first, but I think there are too many variables to figure out if that arrangement would work without experimenting. That leads to my next question about fans and modifications to fans, but I should probably start a different Thread for that.

Thanks again,

Scott

[Scott J]

...I think your solution will work. I measured the distances, and if a 120x120x25mm fan was mounted across the edges of the video cards, a 1/2" above the video cards blowing down toward the MB, it would leave about 1.0" of space to draw air between the fan and the case wall (or window, in this instance). If I understand correctly, one of the fan mounting options for the Prolimatech MK-13 is designed to work in a similar configuration as you described.

On second thought, I don't think the 'edge-mounting' idea will work after all. I forgot about the conflict this solution will have with the Thermalright 5850 VRM add-on heatsink. The Prolimatech approach has the same problem.

Many of the various aftermarket VGA heatsinks (Accelero units, T-Rad2GTX, Musashi, Setsugen, MK-13, etc.) do a better job than the stock cooler, EXCEPT for the VRMs, where the aftermarket heatsinks seem to do poorly and the stock cooler beats them all. The best solution I have found so far to the VRM overheating problem for aftermarket VGA coolers used in conjunction with the ATI/Radeon 5850 (or 5870) is the Thermalright VRM-R3 and/or VRM-R4. Both of these VRM-specific heatsinks (designed for the 5850 & 5870 only) go up over the edge of the video card's PCB board, and this will almost certainly conflict with any fans mounted such that they blow down toward the motherboard. The VRM-R3 radiator in particular (nearly the size of an 80x80mm fan itself) would block the air from an 'overhead' mounted fan, preventing it from blowing air onto the main VGA heatsink.

I think there will also be a problem trying to use any combination of two Thermalright VRM 5850 heatsinks in a two-card 'crossfire' set-up. I have an idea about how to work around it, but I'll cross that bridge when I get there.


Back to square one, trying to find a way to mount fans directly to the heatsink on the first VGA card, while leaving enough room between the fan and the back of the second VGA card for air to get to the fan(s).