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Discussion Starter · #1 ·

Been just over 2 years that my xfx 7970s arrived at my door and I was bursting with excitement at all the reviews, only to find that the damn things won't clock past 1050Mhz.

So having waited 2 years and the market hasn't really progressed, more just got more expensive (pointless upgrading till I can at least get a single card outdoing both for an acceptable price), leaving me with that "itch".

So alas, watercooling it is, my aim is 1200Mhz, but here's the thing, 1 rad, no cpu in the loop (h100i is doing just fine).

Case: Corsair 650D (for rig check sig)
(you'll notice a lot of alphacool, delivery costs direct from them etc etc)

Radiator: Alphacool Monsta 180mm (tis indeed a monsta)
Fans: push/pull Silverstone Air Penetrator AP-181 (don't like the white 182s)
Pump: Alphacool VPP655 - G1/4 IG incl. Attachment
Resevoir: Alphacool Repack Single Bay 5,25" - Rev. 2
Waterblocks: 2x Alphacool NexXxoS ATXP ATI 7970/50
Thermal Paste: Artic MX-4
Fittings: 8x Alphacool HF Screw connector G1/4 outer thread on 13/10 - Deep Black (4x normal/ 4x angled)
Tubing: Hose Masterkleer 13/10mm UV- reactive blue (3/8'ID)
Coolant: Koolance Liquid Coolant Bottle High-Performance UV Blue

Let me know what you think, particularly with regard to the 180mm Monsta handling 2x7970s all by itself, bare in mind this is an 85mm deep rad with overall volume similar to most dual 180mms.


Premium Member
3,702 Posts
Originally Posted by Severe View Post


anyone got a second opinion on this, or am I just wasting my time by trying to cut corners?
If this Monsta 180mm rad is equivalent to a 240mm rad in terms of cooling then it's not enough for two 7970s clocked at 1200MHz (I'm guessing @1.3v) with acceptable temps IMO.

I don't have numbers to back it up, but in general, a decent loop consisting of a single 240mm rad is good for dissipating around 300w-350w of heat at respectable temps.

With the OC on the 7970s, just one of them could be producing more heat than that; two would cause really high temps.

If you're willing to go the WC route, you'll never go back to stock cooling.

Therefore, I would recommend you invest in a case that is more WC-friendly and keep reusing it in future WC builds.

Premium Member
4,140 Posts
Although Monsta rads are very large in volume and look impressive they really only perform a few percent better than a same size thinner rad. That is because they can only effect the same volume of air as a thinner rad.
Rads work by transferring heat energy from water to air. The greater the volume of air affected and the bigger the temp difference the more energy is transferred. A dual rad effects twice the air volume as a single rad, a triple rad effects triple the air volume. So performance between each makes a big jump.
A thick rad effects the same volume of air as a thin rad, so any improvement is made by how efficiently that heat is transferred. That's why all rads are only small percentages different.

Having said that I did see some rad testing on 200mm rads and it compared quite closely to a 360 rad at the same fan speeds. That was external testing though.
The problem is most large fans are low speed and not really designed for pushing through resistance so it may not match the same way in the real world, especially in an enclosed case environment.

There is certainly no reason not to give it a try though. The worst that could happen is that temps are a little higher than with a different rad.
A rad with water 20C above ambient dissipates twice the energy as it does with water 10C above ambient. So if a good rad keeps the water at +10 then a bad one should have no trouble doing +20. The end result is just a 10C difference to the actual temp of what you are cooling.

If you haven't already just make sure you choose the right version of the Alphacool GPU blocks because there is two and only one fits reference 7970's
Edit: Also, from memory the Alphacool 7970 block does not actively cool the VRM section by passing water directly over it. It is much like the XSPC version. The water passes over the core and memory sections and the VRM section has to transfer the heat over.

103 Posts
I'm using an Alphacool UT60 280 with an MCP35x and two Gentle Typhoon AP-15's (120mm -> 140mm adapters) to cool two 7970's and a 3570k. I have been running the GT's at ~1200rpm and the pump at maximum speed. After 24 hours of ~99% GPU load and ~1% CPU load, the GPUs are around 50-54C (~19.5C ambient).

CPU is at stock clock speed and the GPUs are at 1500 memory, 1030 core, if I recall correctly.

I would advise you to get more radiator height/width. Perhaps ditch the H100i and get two 240mm rads.

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