Dual Sapphire Radeon 7990 cooling

[Deleted member 156785]

I've built myself a sweet mining rig but I'm finding it near impossible to cool using fans alone. I would also like the option of overclocking. I'm powering the system with an EVGA 1300W Supernova G2. I'm not interested in water cooling the CPU, since it generally won't be doing much, though I may add it in later. Here's my part list so far:

2 x EK Radeon HD 7990 SE VGA Liquid Cooling Block - Nickel + Acetal (EK-FC7990 SE - Acetal+Nickel)
1 x XSPC Dual 5.25" Bay Reservoir - Laing D5 / MCP655 w/ Blue LED Light - Clear / Silver / Black
1 x Alphacool VPP655 Variable Speed Pump w/ RPM Monitoring - Single Edition
1 x EK Terminal Block - Dual Parallel 3-Slot - Black Acetal (EK-FC Terminal DUAL Parallel 3-Slot)
1 x Alphacool NexXxoS Monsta Quad 120mm Radiator - 80mm Thick!!
6 x XSPC 1/2" x 3/4" Compression Fittings with G1/4" Threads
1 x PrimoChill PrimoFlex Advanced LRT 1/2in.ID x 3/4in.OD Tubing- Crystal Clear (10ft pack)

I already have a bunch high flow/pressure fans 120mm fans. Anything I'm missing? Is the radiator sufficient for two 7990s (technically four GPUs)?

 

[GTXJackBauer]

Welcome to OCFs!

Have you figured how much heat will be generated and how much heat surface will be needed? What Delta temps are you aiming for as well as if you're going for a silent system? I believe that rad is 10 FPI as I know the 60mm version is.

If you're not too familiar with what delta temps you're aiming for, please take your time and read some of our yellow water cooling stickies.

Your choice of hardware is pretty spot on except you lack heat surface to be honest to help you out. You are cooling 4 GPU's total and our usual rule of thumb is 120.2 per chip. If you really want to get some good temps and have a silent system, I would grab another one of those rads or just get 2 60mm quad versions. The more heat surface you have the cooler it will be, ambient permitting of course. If you use those 80mm make sure you do push n pull since its such a thick rad.

One of our members (AJay57) had a similar setup where he had 2 GTX 690s + CPU for his 24/7 and benching rig. He had great temps with them both and still does with his changed setup now. I am sure he will jump in as well.

 

[Deleted member 156785]

I don't care much about it being silent. I have a few of bgears b-blasters, which are supposed to be high pressure/airflow, so I would think push would be enough with that radiator?

I can't actually adequately cool the cards now at stock speeds; I've turned down the frequency/intensity on two of the GPUs by 30-40%, which gives me load temperatures of 90-93C. I'm looking to maintain those temperatures, but at least be able to run at stock, hopefully overclock a bit. I don't care about idle temperatures, since these cards will never be idle. CPU usage will typically be low (with the stock cooler my core temperatures when running cgminer are 60C), so I'm not planning to add it to the loop, and even if I did, I guess it wouldn't need much cooling.

 

[Deleted member 156785]

Ah, I found AJay57's thread. He's using two Monsta 360mm radiators, which is what I was originally going to use (in two separate loops), but was told elsewhere this was unnecessary. The GTX 690 has a 300W TDP while the Radeon 7990 has a 375W TDP. On the other hand, AJay57 was also cooling his CPU.

 

[GTXJackBauer]

Ah, I found AJay57's thread. He's using two Monsta 360mm radiators, which is what I was originally going to use (in two separate loops), but was told elsewhere this was unnecessary. The GTX 690 has a 300W TDP while the Radeon 7990 has a 375W TDP. On the other hand, AJay57 was also cooling his CPU.

He's actually using x3 Alphacool 360 UT60 Rads. More than enough cooling for anything literally you throw it at for years to come.

Can I ask what case this is all going into and what existing system you have running? Curious to see what you have in store for rad locations.

I myself would love to get into bitcoin farming but don't have any AMD GPU's here. Only Nvidia. heh

 

[Deleted member 156785]

This is going into an old Antec 300 that I upgraded from. I had to remove the disk drive bay to accommodate the 12.5" cards! The system has an entry-level Pentium G2020 with 2x4GB RAM. The radiators will be external, positioned horizontally on the ground.

I've really found it confusing researching radiators and heat dissipation. Some sites claim ~150W/120mm fan, others say 200-250W/120mm. On martinsliquidlabs.org they claim 300W@2000RPM dissipation for the 360 UT60. From what I can tell, the Monsta performs 10% or so better than than the UT60. Using the latter figures, that would give me heat dissipation around 660W, which is definitely too little.

On the other hand, the ASUS ROG 7990 has a single 120mm radiator in push/pull, with an additional smaller fan (80mm?) on the card, and is reasonably quiet even at load (37 dB), with load temperatures in the mid 50's. I would be more than happy with mid 80's, let alone mid 50's.

*sigh*

 

[GTXJackBauer]

I don't know nor would I trust a 120mm rad on a 7990. Someone in their design department isn't familiar with watercooling and I would advise THEM to read our yellow intro sticky section.

Martin'slab is the best place to find H20 info. Honestly you need 120.2 per GPU. So 2 of those quads would be enough or even the UT60s. Slap some AP-15s on them and you're off to the races. Only changes I would make is switching the pump to a MCP-35x. Has better head pressure.

 

[Deleted member 156785]

So, I've read about delta-T's, and how 10C is a good delta-T, but how does that translate into CPU/GPU temperatures? Lots of people post how their CPU/GPU are now quite cool under load, but I tend not to care about that. Should I instead shoot for delta-T of 15C? 20C?

 

[Zoinks]

Your water cooling solution should be driven by your own needs. If higher deltas/more noise are acceptable to you then less radiator area and louder fans will get the job done. It all depends on what you expect from your system.

I'll give an example. I am currently running three EVGA GTX 570 Superclocked cards in triple SLI. They are on a dedicated loop with one 480mm radiator and four 2,000 RPM 120mm Cooler Master Sickleflow fans rated at 70CFM. Under full load my GPU temps get to about 56C. The fans are noisier than perhaps a lot of systems built here but it is absolutely fine for my needs. My temps are miles lower than they were on air, and when I put this rig together that is all I really cared about. A few extra DB of noise made no matter to me at all. If, however, you really want an uber quiet system and the lowest temps possible, well then it becomes important and the only way to get that is with quiet fans at lower RPM that move less air combined with lots of radiator surface area.

I don't know what TDP is for the 7990 (I checked the AMD and Sapphire websites and gave up after that), but I imagine that two of them is a lot of heat. My three GTX 570s have a combined TDP of 663 watts, and I have to imagine that two 7990s is a truckload more than that. Based on that alone I think you are going to need more than 480mm of radiator, even if more noise and higher temps are ok with you.

That's my 2 cents.