First off this data is preliminary and does not yet include multiple runs on each block.  We are also waiting on XSPC, Bitspower, Watercool, Swiftech and Alphacool to finish/deliver their blocks. There are three facets to our performance roundup. The first and most important is cooling of the GPU core itself.  The main GPU core chip is what kicks out the most heat on the board and is where the cooling engine design work is concentrated.  These blocks are tested at various pump speeds to show performance vs flow rate.


Testing is performed with a “normal” overclock. +100mV Core, +100mV Aux are run on a reference R9-290, while the core is clocked at 1175MHz and the memory at 1465MHz. This provides a sizeable heatload as will be evidenced by core temperatures being significantly higher at high flow than was the case with the Titan/780 waterblock testing. GPU temperatures are logged by GPU-Z, Dallas one wire temperature probes are used to measure coolant and ambient temperatures and are logged by wintest through a CrystalFontz CF-635. Loading is provided by furmark and a 40 minute warm up is allowed before 20 minutes of data logging is initiated. The warm up occurs before each data point is data logged. MX2 TIM is used and is allowed to burn in over night in order to remove any time-related “curing” effects. The motherboard is a Maximux VI Impact with a 4770K clocked at 4.4GHz and cooled by an EK Supremacy water block. Cooling is provided by an XSPC EX 560 radiator with 8 low speed yate loon fans. Flow rates are measured with a King Instruments rotameter. Multiple high flow QD4/VL4N quick disconnect fittings are used to quickly replace blocks. Here is how the testbench looks without the GPU:

Core Cooling Performance

As expected cooling performance increases as flow increases. There may be a point at which high flow may hurt performance but this is not shown to be within the normal expected flow rates that users normally run.

While the shape of the data is therefor expected there are some points to note. The data is extremely close and there is little difference in performance between the three blocks. In addition in the Titan/780 waterblock testing we saw the EK block to have significantly worse performance at lower flow rates. This has been improved. In addition AquaComputer’s block was significantly higher in restriction and therefore operated at lower flow rates for a given pump speed. This also has been fixed as evidenced by the AquaComputer block having similar flow rates to the EK and Koolance. Flow restriction numbers will be available soon.

VRM Cooling Performance

In our Titan/780 water block testing we measured VRM temperatures by measuring the temperature on the rear of the circuit board under the VRMs. Although this gave an indication of VRM temperature, it really measured the PCB temperature which was greatly affected by how well the neighbouring chokes were cooled. However AMD included VRM temperature probes that can be monitored by GPU-Z. There are two VRM probes. One is located close to the memory on the DVI/HDMI/DP end of the card, while the other is located in the main VRM section near where the 12V power cables will be connected. The first never gets particularly hot. In fact in one case the thermal pads were forgotten that would enable the VRMs to be cooled. The VRM only hit 20C over coolant which is very good. The other VRM temperature sensor on the other hand gets significantly hotter as can be seen in the following plot:

Taking the first three lines that are grouped together we see that VRM performance is spread a little more than core temperature was. Koolance uses the thickest thermal pads (1mm thick) and unsurprisingly has the worst performance. EK decided to use thicker pads for the VRMs than on the 780/Titan block and therefore loses ground to AquaComputer who has the thinnest pads so far. In addition the AquaComputer backplate provides a significant boost in VRM cooling. This was surprising and initially attributed to the “active” heatpipe. My expectation was that the active backplate was somewhat gimicky – a cool feature but one that might not prove to actually affect VRM temperatures much at all. Removing the heatpipe and running with just the “passive” part of the backplate shows this to match expectations. However the large effect of the backplate is mysterious right now. There are two theories – one that it’s providing extra pressure to the block to cool the VRMs, and the second is that there are thermal pads on the backplate that cover more area than the EK for example.

Flow Rate & Restriction

Coming soon!


Like the CPU Block roundup Koolance again proves it’s supremacy in core cooling, but drops the ball with it’s thick thermal pads. However it’s lead is not really enough. 1C is a small gap, however AquaComputer shows that it’s backplate can really make a surprising difference in VRM cooling. As the roundup is not complete then awards can not yet be issued but it would seem that AquaComputer is making a very strong case with it’s all round performance! XSPC’s block is on the bench right now!


  1. Hi stren,
    Great review as always, although I’m curious about the huge VRM-temp improvement with the aquacomputer backplate. What I was thinking, is that possibly just the effect of only a backplate pressing against the back of the card is already enough to get this temperature drop without the need to actively cool it.
    It shouldn’t be too hard to test this since you could just disconnect the heatpipe from the backplate and then look at the VRM temps again after letting the temps settle.
    If you could test this that would be awesome!

    • Hi Jelle

      Yes that would be a good test – I suspect that it is the heatpipe simply because the EK backplate which cools the VRM area similarly does not perform nearly as well. Of course I haven’t taken the numbers of the EK block without the backplate yet so it’s not quite an apples to apples comparison. I’ll try and get that data taken 🙂

      • Awesome, thanks!
        I don’t know about the EK backplate though, it might even be that it just doesn’t contact the VRM area and that it therefore doesn’t give more pressure against the waterblock.

        Will be following this closely, this review has definitely changed my mind about getting a backplate (reversed atx-build) all that’s left now is to decide whether or not I want the active one 😀

        • The EK backplate definitely has thermal pads that contact the VRM area, although the Aquacomputer has slightly more coverage. Also they are different thermal pads 🙂 I was very surprised about the active backplate results 🙂

          • I did not know that about the EK backplate, definitely makes it a little bit more of an apples-to-apples comparison.
            Still curious about the results though, as well as the restriction numbers. Just for fun modeled the AquaComputer block in solid works and let it calculate the pressure drop at 1GPM which was only 10kPa which isn’t that restrictive at all. Might be quite a bit off since I don’t have the block yet and only modeled by looking at pictures. Guestimating the depth of the water channels was the hardest part, and sadly this also has the biggest impact on restriction, but still was pretty promising!

    • Hey Jelle – I did actually test this and the results are up – you were right the heatpipe itself does little, it’s something else about that particular backplate 😉

      • Not that surprising really. Too bad the heatpipe-less backplate is exactly the same as the one with the heatpipe, so you’ll end up with a few extra holes and the cutout for heatpipe. This will most likely push me towards the version with heatpipe even though it doesn’t give a performance boost (although one might wonder how much you get to see the backplate in a reversed-atx build)

        The heatpipe might do something though in a case where the GPU sits in a badly ventilated case. If the surrounding air is as hot as the water-temperature the heatpipe might start to do something, but to measure this you’ll need an insane amount of heatup-time since very little power, if any, will be transferred to the backplate since only the PCB touches the backplate and not actual powered components (like on the titan with it’s VRAM)

  2. Good write up. looking forward to see where the XSPC ranks in this list. From my own experience, running 2 xspc razor blocks, Core temps are 45 under load while VRM 1 is at 55 with an ambient of 25. Pretty close to the the performance of the Aquacomputer blocks = ]

  3. Thanks for the review..I have the Koolance Full Cover block on a Sapphire 290, and am going to be adding a second one in the future. Since you have these blocks, is there anyway you could tell me if it would be possible to use the AquaComputer backplate with the Koolance blocks? The massive drop in VRM temps are very welcome, especially in a mining setup.

    I appreciate any information and look forward to your updated testing.

    • I believe most backplates are compatible but you’ll have to buy aftermarket screws as screwthreads and length of screws are most likely different. My gut feeling is that the AC backplate is so good because it adds thermal pads to a specific area that others don’t. For the retest with the new 290 card I’ve added my own temp sensor to the VRMs and so this should give a clearer picture of actual temperatures 🙂