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Author Topic: Shroudless GPU Cooling?  (Read 4465 times)
catfish
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September 12, 2011, 12:03:17 PM
 #1

Most of us building open frame rigs are using pretty much identical layouts, albeit in different materials and at massive variations in design quality and aesthetics!

We tend to put the logic board horizontally on the base of the rig, then the GPUs standing vertically with the ports facing you (looking head-on at the rig). PSUs are either behind the logic board, or to one of the sides (or both, with dual PSUs and lots of GPUs).

However, virtually everyone keeps the GPU cards intact, with their built-in fans and heatsink shrouds attached. These cards are, AFAIK, designed to be *inside* a PC case, blowing hot air out of the vents in the back. Since the pressure inside the PC case will be higher (in general, not just due to fan performance but also the higher temperature), the GPU cards should act *as designed* and blow air OUT of the port-end vents.

With open-frame rigs, the pressure around the components is pretty constant - everything is open to ambient. I've noticed that all the shrouded heat-pipe-infested GPU cards end up blowing air out in all directions - especially *UP* rather than out of the port-end vents.

Then, most of us (including me) run desk or box fans to blow AT the frame rig. With air blowing *UP* from the cards, and a fan blowing *down* - perhaps dead zones could occur.


So - how about removing the plastic shrouds (and even the fans) from the GPU cards - so the copper fins and heatpipes are open to the atmosphere? Then use the desk fans / box fans to create a *single* stream of air?

Does anyone know whether this would be idiotic, or could be *better*? There's a fantastic home-brew water-cooled 5770 in another thread, where the shroud and heatsink has been removed, and replaced with small-bore copper water piping. I'm not willing to go to water (I may need to resell the cards eventually) - but removing the plastic shrouds and even the fans would be VERY easy.

Surely with a frame rig, those plastic shrouds are doing *more* harm than good - especially when you can guarantee high air flow from an external big fan?

I can't help but think that the shroud + fan design is optimised for positioning within a PC case. The air blowing out between the PCB and the edge of the plastic shroud when mounted in a frame rig suggests it's not working as designed. I don't get this with my two 5850s that I have in a 'real PC' case.


I'm going to try it out - but has anyone else tried first before I trash a 5850 and a 5830?

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September 12, 2011, 02:27:54 PM
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you said removing the plastic casing should be easy, and i totally agree.
Then you said you don't want to trash your card. How will you trash your card if removing the casing is easy?

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September 12, 2011, 02:33:30 PM
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you said removing the plastic casing should be easy, and i totally agree.
Then you said you don't want to trash your card. How will you trash your card if removing the casing is easy?
If the experiment doesn't work, and some aspect of the shroud cools critical components in a way that an 'open' heatsink does not.

In other words, what I meant was not 'trash the card' aesthetically (the shroud can be replaced, as I'm sure you agree), but potentially catastrophically overheat some component.

It's a long shot, but worth asking. For example, I know nothing about how the VRMs work, where they are, or what they look like. But I know they are critical and they also get very, very hot. When I know I have known unknowns (in Rumsfeld-styleee) then I ask questions Smiley

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Richard Rahl
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September 12, 2011, 02:36:05 PM
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So - how about removing the plastic shrouds (and even the fans) from the GPU cards - so the copper fins and heatpipes are open to the atmosphere? Then use the desk fans / box fans to create a *single* stream of air?

The shrouds direct airflow over critical components of the card. Unless you know what you're doing and going for watercooled, I wouldn't suggest it. They serve a purpose and aren't there just to look pretty.

Take off the shroud, heatsink, and fan.... and you are now the proud owner of a $200-$700 ugly ass paper weight.

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September 12, 2011, 03:04:44 PM
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Don't forget that modifying the GPU could blow your warranty. Warranties have been real handing as I currently have 10 GPUs out for repair / replacement.
catfish
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September 12, 2011, 03:44:07 PM
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So - how about removing the plastic shrouds (and even the fans) from the GPU cards - so the copper fins and heatpipes are open to the atmosphere? Then use the desk fans / box fans to create a *single* stream of air?

The shrouds direct airflow over critical components of the card. Unless you know what you're doing and going for watercooled, I wouldn't suggest it. They serve a purpose and aren't there just to look pretty.

Take off the shroud, heatsink, and fan.... and you are now the proud owner of a $200-$700 ugly ass paper weight.
They presumably direct air to the correct places when *inside a PC case*. In an open frame rig, air blasts out from everywhere - even the top of the card where the shroud nearly touches the PCB. If the designers intended the airflow to come out *there* then they'd perforate the top of the shroud, no?

My hunch is that the cooling system is designed for cards mounted inside PCs, where the air is hot.

I have no intention of removing the heatsink!!! That'd be crazy. The idea is to remove the shroud so a *big* fan can blow much larger volumes of cool air onto the heatsink itself. If the fan on the heatsink looks like it's doing anything tricky then I won't. If the heatsink is heavily finned (most of my faster cards have heatpipes anyway) then I may try taking the fan off (assuming the card runs without it) and supply ALL airflow from a high-volume fan.

At the moment, it just looks *so* much like there's a row of cards with tiny fans blasting hot air from one card to another, getting trapped in the shroud, and potentially causing turbulent flow with the big fans I've installed over the frame rigs.

I'll give it a shot with a 5830.

...so I give in to the rhythm, the click click clack
I'm too wasted to fight back...


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cicada
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September 12, 2011, 04:14:47 PM
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I'd underclock that 5830 to start off, I think you're going to find that the shrouded sink + fans cools more efficiently, regardless of turbulence from your external fans.

The fins are generally oriented along the length of the card, not the width, so blowing 'down' on the cards - perpendicular to the fins - won't do much.  You'll need to direct air lengthwise across the card, through the fins, instead.  The shrouded HSF arrangement forces this airflow.  Without the shroud, the air you're blowing at the card is going to take the path of least resistance, which is going to be around and over the heatsink instead of through the narrow passageways between the fins.

I've found that blowing 'down' on the cards actually increases my temps.  Instead, I let the cards exhaust wherever they will, and have a high-velocity desk fan pointed at the rear of the cards, blowing this hot air away.  This method keeps my 5830's ~65-70C in a 98F (36C) closet.

Ignore the heatpipes - you'll notice they're connected to the heatsink at the solid base near the GPU (HOT!) and again along the length of the heatsink through the fins (cooler) where they transfer most of their heat - blowing air at the exposed parts of the heatpipes doesn't do much, as there's very little surface area comparative to the heatsink fins.

By all means give it a shot, I could be completely wrong, but I think you'll find it's difficult to keep things cool without the shrouds.

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September 12, 2011, 04:27:59 PM
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I'm currently running 2x Sapphire 5850 Xtreme without the plastic shroud + 2x 12cm Deep Cool Xfan tied and blowing air at them on the side.
The temperatures on the GPU, memory, and the VRM is lower but only by a bit compared when they still have the shroud on.
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September 12, 2011, 05:06:37 PM
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setting up watercooling removes the shroud... so other than the components covered by the cooling block, what are you all talking about as being a potential problem due to changing airflow???

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September 12, 2011, 05:23:06 PM
 #10

I've been thinking lately that creating a air tunnel to get cool air into the center fan intakes is the way to go. If the GPU cards are hanging above the mainboard then feeding air under the cards, guided into the intake fans from the same side as card #1 (which naturally gets fresh air), guiding with cardboard dividers, would give them all fresh air. Then it doesn't matter so much that the hot air blows out all around as long as the intake is some distance away.

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September 12, 2011, 05:27:30 PM
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I suspect the shroud still directs fan air to the extremes of the heatsink, though I'm interested to see the results
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September 12, 2011, 05:29:04 PM
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setting up watercooling removes the shroud... so other than the components covered by the cooling block, what are you all talking about as being a potential problem due to changing airflow???

Catfish isn't talking about water cooling, he's talking about air cooling without the plastic shroud that covers the heatsink.

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September 12, 2011, 05:36:38 PM
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setting up watercooling removes the shroud... so other than the components covered by the cooling block, what are you all talking about as being a potential problem due to changing airflow???

Catfish isn't talking about water cooling, he's talking about air cooling without the plastic shroud that covers the heatsink.

yeah. i know that.  so what exactly is this change supposed to be then?  the heat-sinks for air-cooled are pretty much covering "same" area/components as the water block.
i'm pointing out that this is a myth.

you do need air movement, the shroud seems to provide direction for that and it serves an aesthetic purpose... but any real miner has good airflow, so the shroud IS useless functionally.

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September 12, 2011, 05:43:32 PM
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yeah. i know that.  so what exactly is this change supposed to be then?  the heat-sinks for air-cooled are pretty much covering "same" area/components as the water block.
i'm pointing out that this is a myth.

you do need air movement, the shroud seems to provide direction for that and it serves an aesthetic purpose... but any real miner has good airflow, so the shroud IS useless functionally.

Take the fan off your CPU heatsink, overclock it and blow air at it instead of through it, and tell me if it's still effective.

The directed airflow through the heatsink is tantamount to the asthetics, they make it 'pretty' because they can.

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September 12, 2011, 05:48:15 PM
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yeah. i know that.  so what exactly is this change supposed to be then?  the heat-sinks for air-cooled are pretty much covering "same" area/components as the water block.
i'm pointing out that this is a myth.

you do need air movement, the shroud seems to provide direction for that and it serves an aesthetic purpose... but any real miner has good airflow, so the shroud IS useless functionally.

Take the fan off your CPU heatsink, overclock it and blow air at it instead of through it, and tell me if it's still effective.

The directed airflow through the heatsink is tantamount to the asthetics, they make it 'pretty' because they can.
nobody is talking about removing the fan.  you just feel like spewing hot air here?

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September 12, 2011, 05:54:46 PM
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So - how about removing the plastic shrouds (and even the fans) from the GPU cards - so the copper fins and heatpipes are open to the atmosphere? Then use the desk fans / box fans to create a *single* stream of air?

nobody is talking about removing the fan.  you just feel like spewing hot air here?

The OP is :-P

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September 12, 2011, 05:57:18 PM
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So - how about removing the plastic shrouds (and even the fans) from the GPU cards - so the copper fins and heatpipes are open to the atmosphere? Then use the desk fans / box fans to create a *single* stream of air?

nobody is talking about removing the fan.  you just feel like spewing hot air here?

The OP is :-P

my understanding is that the main point of this post is about the shroud.  "even the fans" does not seem to be the main objective here. but to each it's own.  if that's the main point you see, so be it.

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September 12, 2011, 06:22:00 PM
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Canary, I respect you and I'm not trying to start anything here, forgive me if you read some tone into my responses I didn't intend.

My point was simply to make it clear that removing the fans is a bad idea.

Sez' solution of tying two 120mm fans to the heatsink has the effect of forcing air through the fins while minimizing air restriction - I think this isn't a bad plan, but as sez stated the effect wasn't pronounced.

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September 12, 2011, 06:57:42 PM
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There is one thing you haven't really account for: Pressure. The plastic shroud directs the airflow that comes from the fan attached to the heatsink. The pressure is still high and is able to push itself through the fins and the shroud. If you take the shroud off, some of the pressure is relieved (The air flings out towards the outside of the fan, kind of like when you sit on a playground merry go round and someone spins it really fast, you'll feel like you are about to be shot off the edge), and the remaining air that gets pushed towards the fins will stop earlier due to less pressure while turbulence remains the same. Now if you got something else thats relatively close (maybe up to 3 inches) thats blasting high pressure air onto the HSF assembly, then it may benefit taking the shroud off, but I would still keep the fan attached, unless the airflow from the outside fan is parallel to the fins of your HSF assembly and it's not blocked by something (plastic shroud, or the fins are folded over each other like in blower-type HSF assemblies such as the reference 5870 HSF)

If you have something going on like a wind tunnel going on, like floating video cards with ribbon cables, and the area with the video cards has like 6 120mm fans all blowing air from front to back, that may be high CFM, but it lacks pressure to push cool air between small, hot crevices (turbulence will slow it down to a crawl). Blower-type fans have very high pressure, which is why you see them in many very high TDP cards such as 58xx, 5970, and 69xx radeons.

TL;DR: If you're cooling with many fans but from a distance, don't take anything off. If you're cooling with 1 or 2 fans that are extremely close to the cards and are very high pressure (delta 200+ cfm), take off the shroud. I would not take off the fan though.

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September 12, 2011, 08:08:22 PM
 #20

I tired this with 4 5830 SAPPHIREs because i originally had them smashed together. i removed the shrouds reapplied arctic silver and ran 4 high speed 200cfm 120mm fans in a closed case. 2 in front 2 in back push pull. I though i would be able to drop my temps by 5c or so, but i did not. My temps went up by about 3c. so i removed them from the case created an open frame rig (just like everyone else's) and they still ran hotter without the shrouds. I think the pressure comment is right on. Even if it appears that a heat sink with single air flow direction design appears the be the best method the cards were just not designed that way.
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