Keeping Dual 7950's Cool

R

REDYOUCH

Supreme [H]ardness
Joined
Mar 17, 2001
Messages
4,521
Just setup my mining rig and am having a hell of a time keeping two 7950's cool.

The case is a Lian Li PC-A04B (http://www.newegg.com/Product/Product.aspx?Item=N82E16811112316) with dual 120's in the front. I have removed the filters to increase airflow and hard-set them to full speed.

Motherboard is an ASUS Maximus V Gene MicroATX. Because of that form factor, there are two PCIe x16 (4 total slots). The two 7950's take up all of the slots. With one card, I can mine all day and keep cool, but as soon as I put in a second one, the temperature quickly increases to almost 100*C.

Any thoughts on how to achieve this? I was thinking some ducting from the front fans directly to the cards, but I think the very small amount of space between the cards may be the root cause. Both cards are MSI R7950 Twin Frozr's (which are very thick).
 
open your side panel and put a box fan at full speed directly :rolleyes:.. (out of sarcasm that work xD).

move to water cooling.. you can try with those GPU bracket for AIO Water cooler Kits or move directly to a custom loop exclusively for the GPUS.. of course the cheaper option its the box fan.. if you have AC in your room then you can make a conduit directly from the AC to the GPUs with the help of a small fan in the conduit that work flawlessly for a friend he used a flexible aluminum duct like This one with a 140mm fan at the start of the conduit and one high speed 120mm fan at the end of the conduit.. it worked perfect for him.. but of course it have to keep the AC 24/7 or during mining periods..
 
As you've found, custom cards are not good for crossfire or SLI unless you have a motherboard which allows for a lot of spacing, and great case cooling. Honestly, your choices are to keep the side panel off and use a box fan or tons of case fans, or going water. Or you could use the cards on a test bench, but you'll still need more cooling and air flow on top of that.

Reference is better for sandwiched CF, although I don't think 7950s are really available anymore....
 
The gene-v is absolute bullshit for SLI/Crossfire. I don't know what the fuck those idiots at Asus were thinking, they should have put that PCI-E 4x slot in between to give more space, but logic doesn't exist with them. I tried pretty much everything, i put some small pieces of wood in between the cards, had a noctua fan blowing in that tiny gap, and still the upper card would have to be downclocked, and kept in a freezing room(Even when the air was close to freezing point the top card was hitting the 70's easily). The only way you can mine is with a riser(remember though the second slot will NOT work with an x1 riser, must do it in the first or x4 slot) or if you water-cool them.
 
Have you undervolted your 7950s? What model cards do you have? honestly blowers are the best for Crossfire setups. If you could feed the fans cool air via a side fan (can you remove the side panel?) that would help a lot. Remove the coolers and apply some aftermarket paste.
 
The cards are MSI R7950 Twin Frozr 3GD5 in non-CrossFire setup. Voltage shows 1087mV in Afterburner. CGMiner 3.7.2 configuration file below:

Code: 
"gpu-platform" : "1",
"intensity" : "20",
"vectors" : "1",
"worksize" : "256",
"kernel" : "scrypt",
"lookup-gap" : "2",
"thread-concurrency" : "24000",
"shaders" : "1536",
"gpu-engine" : "1000",
"auto-fan" : true,
"auto-gpu" : true,	
"gpu-memclock" : "1450",
"gpu-vddc" : "1.15",
"gpu-threads" : "1",
"gpu-powertune" : "20",
"temp-cutoff" : "95",
"temp-overheat" : "85",
"temp-target" : "80",
"scrypt" : true,
"temp-hysteresis" : "3",
"kernel-path" : "/usr/local/bin"

Right now I am running just the single card with no issues at about 620Kh/s.
 
Pic of setup (with 1 card):

mining1.jpeg
 
Oh lord tf3 7950's. That cooler is awful in a sandwiched x-fire config. I'd recommend watercooling them, or buying a new motherboard with better spacing.
 
xIronCrossx said:
The gene-v is absolute bullshit for SLI/Crossfire. I don't know what the fuck those idiots at Asus were thinking, they should have put that PCI-E 4x slot in between to give more space, but logic doesn't exist with them. I tried pretty much everything, i put some small pieces of wood in between the cards, had a noctua fan blowing in that tiny gap, and still the upper card would have to be downclocked, and kept in a freezing room(Even when the air was close to freezing point the top card was hitting the 70's easily). The only way you can mine is with a riser(remember though the second slot will NOT work with an x1 riser, must do it in the first or x4 slot) or if you water-cool them.
Click to expand...

ASUS its not guilty that people are enough dumb to mix 2 non-blower style cards in crossfire/SLI.. thats a great Motherboard one of the few iATX boards that support SLI/Xfire setup in a iATX Form Factor.. people know since the times of Methuselah that custom cooled cards are no good for SLI/Xfire.. its always better reference or non-blower even with the x1 Slot between X16 to have a extra breathing room for the cards, also even with the 2 cards with blower style cooling the top card will always be hotter than the lower ooh and if you remember most iATX case do not have enough expansion slot to allow that kind of extra room between PCI-E X16 cards, most have just 4x Expansion Slots.....

also +1 for riser preferably a good powered riser..
 
You literally get less than 1mm of space between cards, not even a reference card is going to do well with that. It's design could have been done way better, because that PCI-E4x slot is useless anyways if you use a second card. It shouldn't be advertised as SLI/Crossfire capable without specifying you need to water-cool at least 1 card to be able to take advantage of it.

Everything else is fantastic on the Gene-v, don't get me wrong I love the amount of features they packed in it at the price point, but the PCI-E layout is shit.

A powered riser probably isn't needed though, it's just 1 riser. Generally you only get issues when you use 2+ unpowered risers.
 
Just tried again with two cards, open side panel, fans on 100%. It hit my 95*C threshold in about 4 minutes... :-(

I even flipped the PSU and spread the two cards as much as possible (almost 1CM) with hopes that would help...

mining3.jpeg


mining2.jpeg
 
You can run .925 or even .90 volts for the stock 880/1250 settings. I have no idea why your second card is getting so hot though. How hot is the ambient temperature? You can also try taking the coolers off, cleaning off the cores and applying new thermal paste, it can help with temps a bit.
 
Just tried .925 and hit the same result. It looks like the stock settings are 1188mV, 960MHz core, 1250 MHz memory.

I think I may just get a 140mm fan and cut a hole in the case side.

I am leaning towards it not being a thermal paste issue, as single cards run perfect for days on end. Only when two are installed do I encounter issues.
 
small case.

how are you getting rid of the heat in the case? I see all your fans are set to intakes. Do you have a side panel fan?

I would put the Side Panel fan to intake, and the other 3 fans to exhaust. This way Cool air enters where the gpu's are then the hot air is pulled away from the cards. Remember 7950's use more wattage than your cpu, so with dual 7950's that is a lot of heat to get rid of. Having most of your fans set to intake will not help reduce the temperatures if the 500 watts of heat is trapped in your case.
 
I just checked and found that one of the upper 80mm fans was set to intake (I swapped it to exhaust). Now, the PSU, rear, and top fans are now exhaust, and the front two 120mm are intake.

I reapplied TP and at 1.15v, 900/1250, the temps are hovering around 90*C (which I think is very high). Ambient temp from motherboard is 31*C. The lowest I can get the 7950 with 0 load and 100% fan is 44*C (that also seems high to me).
 
1.15 is way too high I think. Try 0.900 and 800/1100 core/mem.
 
xIronCrossx said:
The gene-v is absolute bullshit for SLI/Crossfire. I don't know what the fuck those idiots at Asus were thinking, they should have put that PCI-E 4x slot in between to give more space, but logic doesn't exist with them. I tried pretty much everything, i put some small pieces of wood in between the cards, had a noctua fan blowing in that tiny gap, and still the upper card would have to be downclocked, and kept in a freezing room(Even when the air was close to freezing point the top card was hitting the 70's easily). The only way you can mine is with a riser(remember though the second slot will NOT work with an x1 riser, must do it in the first or x4 slot) or if you water-cool them.
Click to expand...

I understand how the problem is frustrating, but the Gene V is a mATX board with the Z87 chipset isn't it? mATX boards in general are horrible for custom cooled crossfire or SLI, and it doesn't help at Z87 has fewer PCI express lanes which prevents motherboards from having flexibility with slot choice.

One thing that can be done is getting an x79 platform - x79 motherboards have more pci express lanes and therefore you can use whatever slots you want for crossfire or SLI which can help the problem a lot. Or you can get a Z87 motherboard with PLX, but those motherboards cost way too much (450$+).

I guess the main thing though, is that the Geve V not working well in this case really isn't a problem with the design, it's more related to the fact that Z87 has limited PCI express lanes which necessitates the upper two slots as being the only usable slots for crossfire. This is also compounded by the mini ATX design which forced asus to use that slot positioning from what i'm guessing.

All in all though, I really feel that custom cards are a horrible choice for SLI or crossfire. I used lightnings in SLI and it was just....an evening of pain to get working. I have a full ATX motherboard and EATX case though, and I was only able to get it going with tons of case fans, although I *was* able to get it working. I don't think a mini ATX board would work at all, though. I think the best answer in the OP's case is to get a riser, switch to a full ATX x79 platform (if cost is no issue) or switch to reference blower cards. Perhaps a test bench with box fans pointed at the setup could work as well.
 
xIronCrossx said:
1.15 is way too high I think. Try 0.900 and 800/1100 core/mem.
Click to expand...

**AWESOME**

Good call, that appears to have fixed much of the issue. Now hovering at 60-75*C on with both cards at full load.

CGMiner.conf configuration:

Code: 
"gpu-platform" : "1",
"intensity" : "20",
"vectors" : "1",
"worksize" : "256",
"kernel" : "scrypt",
"lookup-gap" : "2",
"thread-concurrency" : "21712",
"shaders" : "1536",
"gpu-engine" : "800",
"auto-fan" : true,
"auto-gpu" : true,	
"gpu-memclock" : "1100",
"gpu-vddc" : ".9",
"gpu-threads" : "1",
"gpu-powertune" : "20",
"temp-cutoff" : "90",
"temp-overheat" : "80",
"temp-target" : "70",
"scrypt" : true,
"temp-hysteresis" : "3",
"kernel-path" : "/usr/local/bin"
 
Whoa. Not bad. Glad you got it working OP, and a tip of my hat to xironcross! I didn't think of undervolting.
 
xoleras said:
Whoa. Not bad. Glad you got it working OP, and a tip of my hat to xironcross! I didn't think of undervolting.
Click to expand...

The gene-z we have is a z77, but I know I am going a bit over the top with my rage but it's just frustrating. And the Twin Frozr is one of the weirdest 7950's I've ever seen. That thing's power usage and heat goes down the drain when you under volt it a little bit. The hash rate for mining does take a hit, but it actually isn't as bad as I thought. The max I ever got out of it was around 600 kh/s, if you under volt and under clock it you can lose up to 100 kh/s or even 150kh/s, but the power usage goes down over 70 watts on one card and the temps also do.
 
I might have spoken too soon. GPU 0 is still hitting 85-86*C, which is not terrible, but not something I would want long term. Ugh... I might need to sell one of the GPUs and put the money towards a Butterfly Labs card...
 
I would suggest you just get an x1-x16 riser, powered if you'd like. Run your case open, get some pieces of wood and just put the top card on that. Temperatures will plummet I bet :)
 
I'd sell the cards and try to find 2 reference 7970's. Reference coolers are fine when sandwiched but non reference style just get desperate for air and obv overheat.
 
Hate to revive an old thread, but thought it would be good to give you guys a final update.

One of the cards was a dud. It would overheat on stock speeds with the lowest intensity no matter how good the cooling situation was.

I'm returning it to Amazon and only buying from trusted [H] members in the future.
 
xIronCrossx said:
The gene-v is absolute bullshit for SLI/Crossfire. I don't know what the fuck those idiots at Asus were thinking, they should have put that PCI-E 4x slot in between to give more space, but logic doesn't exist with them. I tried pretty much everything, i put some small pieces of wood in between the cards, had a noctua fan blowing in that tiny gap, and still the upper card would have to be downclocked, and kept in a freezing room(Even when the air was close to freezing point the top card was hitting the 70's easily). The only way you can mine is with a riser(remember though the second slot will NOT work with an x1 riser, must do it in the first or x4 slot) or if you water-cool them.
Click to expand...

I switched to a a GENE IV to an MSI M-POWER board so I had more room to crossfire. Unless you have a ATX case, most M-ATX cases will have only 4 PCI-E slots. Putting that x4 in between would force your solution to take 5 PCIE slots, which nulls the compact design of a lot of M-ATX boards
 
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