Card air exhaust

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Just noticed that some of the gpus I have, exhaust the hot air through the back (end farthest from the pcie slot or the video connectors). Is this common to most? This changes some of my ideas about how to put the cards in the rig, and point the frame’s fans.

If this is rather common, then it doesn’t help alternating long and short cards. The longer card would then suck in the hot air from the shorter cards. Would need to put together only long with long cards and short with short. Also, shorter cards should be above the longer ones. This is for an open frame rig and not a hanging wireframe

Then the fans should push the air towards the back of the card. Thus moving the air away from the card. I’m doing my first rig, so trying to figure the mechanics of the air circulation.

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Just realized that the frame will probably not have a way to mount the fans (still waiting for it to arrive) on the forward side of the cards, but closer to the back of the cards. Since fans would push the air in a conical way but suck the air from all around the entry side of the fan, there wouldn’t be a way to force the exhausted air from the cards to go the fans.

Probably it will move some of the air but imagine the hot air would dissipate more than move towards the fans. hmmm Might have to try the fans in both directions and see if one works better

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Had some smoke blow into a frame fan, and it does a good job pulling that air from 3-4 inches away, any further and the pattern becomes turbulent. Having the exhaust fan further away wouldn’t allow for proper removal of the air, since it would probably start pulling air from all around.

This was done with the default speed for the fan from the cpu board (50%). Might improve at higher speeds.

Pushing air onto the smoke did remove it, but not enough smoke to see how far the fan could push the air in a smooth pattern.

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Got some extra fans to push air from the forward end of the card (where the connectors are), and inverted the rear (near the pcie power connectors) to exhaust. I left the original fans to pull the air out, to insure air is moving correctly. Wasn’t too sure just blowing air on the cards would exhaust the air towards the rear. In case anybody is interested, I zip-tied the fans to the support where the cards screw on.

I got a two-level open frame similar to the aaawave (but a Chinese version). There are several other vendors selling similar designs.

These frames are poorly designed since the airflow is opposite of what it should be. The cards exhaust the heat towards the rear, so the airflow should pull that air away from the cards. Having air blown towards the card from the rear, causes the card to move that heat back into the card.

Guess the enclosed cases move the air correctly, but was a bit space-constrained, so this frame worked better for me.

Here is a table with my results. Temp1 and fan1 are pushing the air as the rig was designed, and temp2 and fan2 are with both fans (pushing air on the forward end and pulling from the rear)

The temps didn’t change much, but the fan’s speed dropped for most cards. Guess the msi has issues (feels a bit flimsy)

card	temp 1	fan 1	temp 2	fan 2
0	58	69	57	58
1	68	73	58	67
2	56	71	57	50
amd	50	28	43	28
3	58	67	56	59
4	55	42	54	37
5	56	69	56	69

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I was thinking 16 fans are too many lol, so I wanted to try disconnecting some.

Since I have them wired by sections it is easy to turn off some. However, not sure I can turn them off. Strangely enough, sometimes disconnecting one layer’s fan affected the other layers gpus.

The rig has small cards below and large cards on the top layer. All the eth gpus but the second are on the top layer.

Also seems that the air works a bit chaotic, since after perturbing the flow it didn’t quite returned to the same fan speeds. I’m considering the fan speeds to correlate to how well ventilated that card is.

initial state

bottom forward (the side that connects to the video signal cables) disconnected

top forward

bottom rear

top rear

final state

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Continue playing with the airflow, and tried side panels. Cut some cardboard to cover part of the frame. Left part uncovered, on the side of the frame, where the gpu exhausts heat.

If I cover both sides the speed of the fans rises. So I only added it to the side where the heat is exhausted. Interestingly, covering only one side affects cards on both ends!

Changed the flightsheet, so it is hard to compare and added another card. I’m not comparing the numbers I had before.