Alphacool NexXxos NVXP-3 GPU Waterblock Page: 1

Alphacool are one of the major watercooling companies. Especially popular in Europe, Alphacool produce some excellent watercooling gear. We reviewed their Extreme Pro kit in our "Battle of the Water Cooling kits" a while ago and were most impressed.

With today's GPU's becoming faster and faster an despite die shrinks, heat is increasing. Watercooling is also becoming more and more widespread as a way of cooling your PC. With this in mind I purchased an Alphacool NexXxos waterblock for my 7900GTX to see how it performed.


Alphacool have gone down a strange route with the packaging of the NexXxos block. It comes in a retail plastic package, with a piece of paper inside, folded over to contain the smaller parts. The block itself is inside a plastic bag with no padding to protect it at all.

nexxxos block

The rear of the packaging has some blurb about how quiet watercooling can be and is marked with which version of the block is inside.

alphacool nexxxos

There is nothing useful on the packaging about the block at all really apart from which one you have got and what it fits: which one would assume you already knew.

The Package

Alphacool have provided you with everything you need to mount the block onto a graphics card. There is also a decent set of instructions, albeit worded slightly confusingly.

package nexxxos

Not too bad - thermal pads for the RAM and thermal paste for the GPU core, along with allan keys to do up the screws.

However: after I started assembling the block I realised Alphacool had not put in any barbs at all. Now whilst this is most likely because they do not know what size tubing you are using, this is pretty annoying and a sad omission. Companies like Swiftech and Eddie will give you barbs (and usually enough choice to suit any system). A bit of a disappointment in all honestly.

Let's see if Alphacool can make up for it in the design and function of the block...

Alphacool NexXxos NVXP-3 GPU Waterblock Page: 2

The Block Itself

The Alphacool block is made up of a solid copper full cover base that has been milled down to a very nice finish. There is a channel for the water to run over the memory modules and hit the contact area where it is spread out with these channels.

nexxxus flow

The copper base is covered by an acrylic top, which makes the block very nice to look at. This is sealed by rubber "o" rings and seems to be pretty water tight.

nexxus top

The finish of the base is pretty nice in all honestly. It is very flat and even though the packaging the block came in was pretty un-protective, the block seems to be fine.

block finish nexxxos

It is worth noting that Alphacool say that you should clean off the base with some cleaner. This is good advice and I always do this on any block I install anyway. I used TIM cleaner and the finish came up even more impressive than before.

finish #2 nexxxos

That looks pretty impressive to me. I also put the block on some glass and found that it was very flat.

The block has inlets and outlets clearly labelled, making it very hard to get the flow wrong.

inlet nexxxos

These are 1/4" BSP and should let a decent amount of water in.

When I first looked at the block I did wonder how it would fit the inlet and outlets, make contact with the RAM AND the GPU. Here's the answer: it is sloped in design.

nexxxos side view

As mentioned previously - the block does not come with any barbs at all. I am using this with my high-flow 1/2" setup so I acquired some 1/4" BSP to 1/2" Bar connectors.

with barbs nexxxos

Looks pretty nice so far - let's see how it performs

Alphacool NexXxos NVXP-3 GPU Waterblock Page: 3
Test Setup

As I am using a 1/2" ID setup on my watercooling I attached the 1/4" BSP to 1/2" Barbs to the block.

The test rig used is:


Intel Conroe E6600 @ 3379MHz
Asus P5W DH Deluxe
Club3D 7900GTX 512mb


Aquacomputer Evo 360 Radiator
Danger Den 3.5" Bay Res
Laing D5 Pump
Swiftech Apogee CPU Block
Clearflex 1/2" ID Tubing
Jubilee Clips to seal it

I added some Green UV Water Dye and the appropriate amount of Zerex Watercoolant.

The loop was left to leak-test for 12 hours prior to testing.


Idle Tests were performed by leaving on the PC on for 30 minutes and then recoding the temperature using the nVidia monitoring software, getting the average result over a 30 minute period.

Load Tests were gained by first running a loop of 3DMark06, then running RTHDRIBL. The temperatures were recorded over a 30 minute period, and the average result obtained.

All of the tests were performed at an ambient temperature of 25°C.

Overclocking was done using nVidia's forceware drivers and using the coolbits registry hack.

Alphacool NexXxos NVXP-3 GPU Waterblock Page: 4

Installation of the Alphacool NexXxoS was fairly easy. The instructions given are pretty detailed, although some parts are slightly unclear.

I started off with this:

club3d 7900gtx

A Club3D 7900GTX 512mb

club3d 7900gtx nexxxus

The first step is to remove all of the screws off of the back of the card. This is pretty easy and you should end up like this:

naked 7900gtx nexxxus

Here you see the back of the excellent copper cooler/aluminium of the 7900GTX. Thermal pads are used on the stock cooler.

The next step is to clean the card off.

clean 7900gtx nexxxus

Then prep the card with Alphacool's included thermal pads. These are backed with sticky stuff to get them to attach to the RAM chips. In the test I used AS5 on the GPU core (so as to keep all of our water-block tests consistent). Alphacool did include something that looks like a silver based thermal paste for the GPU.

alphacool nexxxus prepping

Alphacool include screws that come with springs. You have to use the included hex keys to screw these up. I had to make sure that these weren't too tight and this can bend the board.

lphacool nexxus

Here is the block installed. As you can see, Alphacool include a backplate for the mounting.

front view mounted alphacool nexxus

As you can see this looks pretty damn good on the card. Note that Alphacool does not include anything to cool the PWM parts of the card so I have kept this installed from the stock card. Alphacool do provide a water-cooled PWM block, but this is extra and due to using larger tubing I could not use this.

The card looks pretty good once in place. One bad thing that I noticed was that the fact that the barbs stick up in the case means that you would not have room to close the door in a slim case. My Lian Li PC70b is such a case and I had to remove a case fan to get the loop to fit.

nexxxus installed

This eventually produced the kink in the system that you can see above. Luckily, this happened after the testing was complete.

nexxxus installed close up

nexxxus installed

The block looks pretty nice installed but how does it fair in the testing?

Alphacool NexXxos NVXP-3 GPU Waterblock Page: 5
Page <script type="text/javascript" src=""></script> Posted 12/08/2006
Author: Matthew Kemp (kempez)
Hardware Acquired: Specialtech

Test Results

Here are the idle test results when compared to the stock 7900GTX cooler:

idle temps nexxxos

As you can see the idle temperature does not tend to go down much at all from the stock cooler. This is perhaps due to the stock cooler being able to cope with the idle temperatures pretty easily. A 4°C drop isn't too bad though.

The load results:

nexxxos load temps

Here is where the NexXxoS really shows us what it can do. The temperatures at load only went up 8°C over idle. This is a drop of 16°C over the stock cooling solution.


I did a quick test of the overclocking increase this reduction in temperature would give. I was able to overclock the card to 717/870. This is an increase on the stock cooler of 7MHz Core and 5MHz memory. This gives an indication of what could be achieved for the serious overclocker - if voltages were increased in the cards BIOS you could get some excellent speeds.

Alphacool NexXxos NVXP-3 GPU Waterblock Page: 6

The Alphacool NexXxoS is a great block for watercooling, but I have to say that this is perhaps more suited to smaller-bore systems such as 1/4" or 8mm. Alphacool cooling systems are generally based on this type of tubing so the block would suit a system such as Alphacool's excellent Xtreme Pro kit. This is more due the case size restrictions than anything else. I had a kink in my system after a while due to the angles being tight.

Having said that, the block still performed very well and certainly is a good waterblock for this high-end card. The looks of the block would suit any system with a case window and the clear acrylic would really show off a system with UV glowing water in it.

The water-block can be found for sale at Specialtech at the excellent price of £35.85. This makes it a pretty attractive proposition.

The Alphacool gets the Overclock3D recommended award and the Value for Money Award, with a score of 75%.

oc3d recommended

value for money


+ Great looking block
+ Decent cooling
+ Great price
+ Fairly easy to install


- Lack of barbs with the block unlike some competitors
- Makes the loop stick out a bit
- Bad packaging could easily damage the block surface
- Not suited to larger bore systems
- Instructions need some working on

This was a personal purchase from SpecialTech

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