Alphacool NVXP-G8 waterblock Page: 1

It is a well known fact that in the quest for faster processors and the subsequent increase in performance, there is an unfortunate by-product...heat! Heat is the absolute enemy of the overclocker and performance enthusiast, period! Heat not only reduces the effective overclocking headroom of a particular component, but it also, if left unchecked, can lead to failure in the long run.

With the introduction of ATI/AMD and NVIDIA's latest generation of graphics cards - the 2900 and 8800 series particularly, heat has now become a real issue for graphics card manufacturers and no longer remains a problem exclusive to CPU's. There is a clear need for better cooling.

Subsequently water-cooling is really beginning to become a viable mainstream alternative to traditional air-cooling measures. No longer is water-cooling purely the domain of the hardcore overclockers, but increasingly, it is beginning to make its way into more and more regular users homes.

The thirst for for faster graphics hardware, and consequently, the said hardware having to play catch-up with software developers (read: next gen games); alternative cooling methods are needed to tame the heat. So how do we look towards cooling these GPU's more efficiently...With water-cooling of course!

Alphaccol webpage

Alphacool is a name synonymous with water-cooling hardware. The German based company made a name for itself by producing quality, well-performing hardware for the PC enthusiast. However, in recent times it seemed that they simply dropped off the radar, allowing competitors to muscle in on their hard-earned market share.

Today, a revamped Alphacool seeks to restore itself back to the position that it held in the past, and continue on with manufacturing high-quality hardware as a commitment to both their current dedicated fan base and you, the prospective customer. The effort being made by Alphacool to regain lost ground is evident. From the fresh and enticing web page, through to the updated product lines, Alphacool is on a mission!

Alphacool NVXP-G8

Today I have been given the opportunity to review the new Alphacool NexXxoS NVXP-G8 8800GTS full-cover water block which promises considerably higher flow and performance over its older sibling the NVXP 3. During the performance review today the Alphacool NexXxos NVXP-G8 will be going head-to-head with another full-cover water block - the EK FC8800 GTS.

Anyway enough of my rambling, let's get acquainted with the review specimen...


The Alphacool NVXP-G8's specifications were taken from SpecialTech's website, due to Alphacool not having the product information on their own site.

Dimensions (L x W x H):       
 180 x 89 x 26mm
G 1/4" 
Flow Through:                       
4.2 to 4.3 l/m (252 to 258 l/h)

The NVXP-G8's specifications certainly look ok on paper, however, there are 2 areas that really stand out. Firstly, the NVXP-G8 weighs in at a smidge under 800 grams. That is one weighty water block especially when compared to the 600 gram EK FC8800 GTS...someone needs to go on a diet!

Secondly, the NVXP-G8 boasts an increase in achievable flow over the previous generation of the same block. It'll be interesting to see how this equates to real world performance when pitted against EK's best.

Let's head over the page and have a closer look at the Alphacool NexXxos NVXP-G8 8800GTS water block to see what you get for your money...

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Packaging and Contents

When I received the new Alphacool NVXP-G8 water block it came in a bubble pack reminiscent of those used by memory manufacturers, but just a little deeper to accomodate the water block. The packaging in its current format offers no protection what-so-ever from over-zealous couriers. The water block itself is kept in a zip-lock plastic bag and features a silica gel sachet to minimise the effects of tarnishing or oxidation.

Alphacool NVXP-G8 packaging front

Chris Banks (International Sales and PR Manager for Alphacool GmbH) has told me that they are currently in the process of renewing all the packaging for their product lines, and when the new packaging is available it should look something like this.
New Alphacool packaging format

I'm sure that you will all agree that the new packaging should provide significantly more protection.

Included in the packaging is everything that you need to water-cool your GPU, with the exception of barbs. Alphacool doesn't supply barbs with their hardware simply because they like to allow their customers to make a choice. All reputable retailers should provide a choice of barbs with the NVXP-G8, so bear this in mind.

Alphacool NVXP packaging contents

Included in the packaging is the following items:

* 1 x Alphacool NexXxos NVXP-G8 8800GTS water block
* Mounting hardware
* Thermal pads for memory, mosfets and VRM's
* Thermal adhesive
* 1 x allen key

A Closer Look

There's a saying that first impressions are usually lasting ones...and the Alphacool NVXP-G8 is very stylish to say the least. Again like the Alphacool NexXxos X2 Bold CPU water block that we recently reviewed, it even allows for the insertion of coloured/UV LED's into the sides of the perspex top if you are so inclined.

Alphacool NVXP-G8 top view Alphacool NVXP-G8 top view reversed

Alphacool NVXP end-on Alphacool NVXP end-on_2
Alphacool as a company are very commited to producing water-cooling hardware that does the job well. Further, they use thermal-imaging technology to assess the hotspots on a particular piece of kit, and design their cooling solutions around alleviating them. Although the NVXP-G8 looks very nice and the water channel routed inside the perspex looks very cool, it's a sure bet that it concentrates on the high-thermal areas of the 8800 GTS graphics card. Particularly the 8800GTS GPU core, memory and the voltage regulation modules (VRM's).
Alphacool NVXP-G8 underside Alphacool NVXP-G8 underside_2

Alphacool NVXP underside_3 Alphacool NVXP side-on shot

The quality of the lapping on the base of the block is exceptional. The only real marks that can be seen at the points of contact are the feint circular marks of the lapping machine. I'd even go as far as saying that the lapping on the NVXP-G8 is better than that of my EK FC8800GTS. Nice work Alphacool!

However, there is one feature of the Alphacool NVXP-G8 water block that I find just a little odd and it is the fact that you are restricted to having the inlet and outlet in one position/configuration only. I really like how configurable the EK full-cover water blocks are! Whilst it should work perfectly well with a single card setup, those with SLI may be less enthusiastic about the inclusion of some tight, flow-restrictive bends in their loop.
EK FC8800GTS barb configuration
waterblocks compared
Alphacool NVXP-G8 installed

Let's head over the page and see how we're going to test the Alphacool NexXxos NVXP-G8 water block...

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Testing Methodology

For the testing phase of the review I have chosen to test the Alphacool NexXxos NVXP-G8 against another well known water-cooling block - the EK FC8800GTS. A Laing DDC Pro pump with OCLabs alternative top will be used to assist in making a comparison. I shall be looking specifically at pressure drop, flow resistance and cooling performance from within a water-cooling loop. All tests will be run 3 times to ensure the elimination of any oddities. I have included the setup details below:

Pressure Drop

For the pressure drop test I used a 25L portable water container filled with 20 litres of water, with a 1/2" plastic threaded barb placed in the bottom to represent the reservoir. A stop tap was inserted immediately after the 1/2" barb to allow for a faster water-block change. The True-Flow pressure meter was used to record the head pressure per 1 minute testing cycle. The pump was primed and let run for a short period to ensure that no air bubbles were left in the loop. The water was allowed to run back into the container after passing through the pressure meter meter via a 'T' connector in order to minimise wasted time between water block changes.

The first run made was with only the pump and pressure meter included in the loop and the water pressure noted. Then for second run the Alphacool NexXxos NVXP-G8 water block was included into the loop and the drop in loop pressure recorded. The same procedure will be followed for the EK FC8800GTS water block.

* 1 x Laing DDC Pro pump with OCLabs alternative top @ 12v
* 1 x Alphacool NexXxos NVXP-G8 and EK FC8800GTS water block
* 1 x Powertech variable DC power supply (quoted accuracy /- 0.2V)
* 1 x Multi-meter
* 25L portable water container
* 1 x Glycerine filled True-Flow pressure meter. (kPa/psi)
* 1/2" ID XSPC tubing
* 1/2" barbs
* 2 x stop-tap fittings

Alphacool pressure test EK Pressure test


In a similar test to the pressure drop testing above, the flow test will highlight just how much the water blocks restrict the natural flow of the watercooling loop. Utilising a very simple setup consisting of a pump, I/2" ID tubing, water blocks, bucket and a stopwatch we will see how far removed from the absolute flow of the pump, that the water blocks hinder flow.
Running the pump into the bucket for one minute and then measuring the amount of water pumped will be the 'absolute flow' of the pump.

To calculate the flow-loss or restriction of each water block, they will each be included into the loop (one at a time) and the same procedure followed. The flow rate will be recorded in Litres/ hour. All simulations will be run 3 times each to ensure uniformity of the results and an average then taken.

Variable PSU Flow test setup

Loop Simulation and cooling performance

I have decided to impliment a control setup for the testing phase of this review. In doing so I have replicated a watercooling loop similar to that in conventional water cooled setups, but it will include the GPU alone and should return consistant and unbiased performance results. The open loop that I have chosen to run with should give quite a good indication of how the Alphacool NexXxos NVXP-G8  water block would perform in your system. The Alphacool NexXxos NVXP-G8's performance will be assessed at the Laing DDC Pro's operating voltage of 12 volts. For each seperate run, the pump was allowed to run for 20 mins to ensure the evacuation of all air from within the loop. The temperatures were taken at 30 minute intervals to allow them to 'settle'. RTHDRIBL will be used in order to simulate graphic load. Due to low maximum resolution of my CRT monitor, RTHDRIBL will be run at 1280 x 960...whilst it isn't perfect for stressing the graphics card totally it should still give some comparitive results.

I have recorded temperatures at idle, load and and an overclocked loaded state; all GPU related temperatures will be taken using RivaTuner vers 2.06 and water/ambient temperatures were taken using a common household mercury thermometer. The mercury thermometer was allowed 5 minutes to aclimatise to air and water and then the temperature recorded. The setup used has been included below:

* 1 x Laing DDC Pro pump with OCLabs alternative top @ 12v
* 1 x Alphacool NexXxos NVXP-G8 and EK FC8800GTS water blocks
* 1 x Powertech variable DC power supply (quoted accuracy /- 0.2V)
* 1 x Multi-meter
* 1 x Tribal Overkill reservoir
* 1 x Toyota Camry heater core
* 1 x Scythe Minebea 120mm cooling fan
* 1/2" ID XSPC tubing
* 1/2" barbs.
* 1 x Intel e6600 processor
* 1 x ASUS P5B Deluxe wifi/App motherboard (bios version 1101)
* 1 x ASUS EN8800GTS graphics card (640Mb version)
* 2GB Corsair XMS2 PC2-6400 RAM
* Antec NEO EarthWatts 500W PSU
* 80 GB Western Digital SATA II HDD

Loop simulation

Please follow with me over the page to see the test results...

Alphacool NVXP-G8 waterblock Page: 4

You can see from the graph below that there is quite a considerable pressure drop for both GPU blocks. However, the Alphacool NVXP-G8 takes first place over the EK FC8800GTS, simply because it facilitates the least amount of 'head' loss.

Head pressure comparison

The Alphacool NVXP-G8 proved to be the most restrictive block of the two tested, with the EK FC8800GTS allowing 100 litres/ hour of flow more than the Alphacool. It will be interesting to see how much of an effect the reduced flow has on the actual cooling performance of the water block. The graphs at the bottom of the page best reflect this.

Flow comparison

I was quite impressed with the cooling performance of the Alphacool NVXP-G8. However, the EK FC8800GTS managed to provide a slightly better overall cooling capacity at load, and when overclocked.

My ASUS EN8800GTS graphics card is not a bad overclocker, and both water blocks managed to get the core clock up to 663Mhz from the default of 513Mhz. Which is an increase in core clock of around 29%.  Overclocking the memory on the card proved a little better too with the Alphacool NVXP-G8 managing to get the memory to 983Mhz, and the EK FC8800GTS to 1020Mhz, respectively.

Alphacool performance chart

Ambient Temperature - 24.3 degC

(Water Temperature)
30.8 DegC31.4 DegC32.9 DegC

EK cooling performance

Ambient Temperature - 24.6 DegC

(Water Temperature)

31.4 DegC32.3 DegC 33.5 DegC

All things considered the Alphacool NVXP-G8 provides solid cooling performance. Let's head over the page to see how it performed as a whole...

Alphacool NVXP-G8 waterblock Page: 5

Conclusion and Final Thoughts

So how well did the Alphacool NVXP-G8 perform in todays review?

Well the Alphacool NVXP-G8 is certainly a quality made product...something that we've come to expect from Alphacool. The attention to detail and dedication to producing a well-performing product is evident from the very moment that you cast your eyes on the product. Admittedly, the look of the water-block may not appeal to everyone, but  hardware aesthetics can be a personal thing. When the new line of packaging is introduced by Alphacool GmbH instead of the plastic blister pack we received, it will both compliment and protect a little better.

It is a well known fact that 'GPU only'  water blocks tend to perform better than their full-cover counterparts. However; quite a few enthusiasts tend to prefer full-cover water blocks over the alternative simply because they compliment their chosen setup better. Personally I like the look of a full-cover water block and therefore accept the cooling performance hit that comes along with the owning one. That being said, the Alphacool NVXP-G8 performed more than admirably in our review today and would be well suited to any high-end water-cooled rig.

Alphacool NVXP-G8

Looking at the Alphacool NVXP-G8's performance today there are a couple of areas that need further discussion. Alphacool's decision to run with thermal pads for the 8800GTS' memory IC's admittedly makes it considerably easier and potentially cleaner (when installing), but in the end proved detrimental to the resultant memory overclock. The EK FC8800GTS on the other hand requires the application of Arctic Silver Ceramique to the memory, which today provided the best result by taking the memory overclock from the default of 792Mhz to 1020Mhz. Perhaps this is something that Alphacool can look at further. The included thermal pads definitely don't transfer heat as efficiently as thermal paste. Furthermore; to Alphacool's credit, the NVXP-G8 was also able to take my GPU's core clock from the default of 513Mhz to 663Mhz; an increase in core clock performance of 29%.

Secondly, the weight of the Alphacool NVXP-G8 is an area of particular interest. Weighing in at around 800 grams the NVXP-G8 is certainly a meaty piece of water-cooling hardware, and although it cooled my GPU almost as well as the EK FC8800GTS, the EK water block does so at around 200 grams lighter. Whilst the NVXP-G8 didn't cause any bowing of the graphics card pcb, I can't be sure that the weight of the block wouldn't cause bowing due to stress in the future if given a longer period of usage.

The NVXP-G8 also exhibited slightly more flow restriction when compared to the EK FC8800GTS, so you will need to factor this into the equation when planning your water-cooling loop. If you were going to utilise the NVXP-G8 as well as a CPU block and/or NB block, then you would do well to include a high flow pump like the Laing DDC Ultra into your order, to offset the restriction.

Pricing for the Alphacool NVXP-G8 is extremely competitive, and you can get your hands on one from the lads at SpecialTech for  £54.21 , inc VAT 17.5%.

Let's have a look at the breakdown:

The Good
• Solid performance
• Quality build from a trusted name
• Attractive looks and appeal
• Facilitates less pressure loss than the EK FC8800GTS
• Ease of installation

The Mediocre
• Weight
• SLI users may baulk at the static positioning of the barbs

The Bad
• Nothing to report

Today I have decided to award the Alphacool NVXP-G8 water block the Overclock3D Recommended award based on its excellent performance today. I believe that if Alphacool can address the issues that I highlighted today, then the NVXP-G8 could be the full-cover water block of choice for many enthusiasts.

Recommended award

Thanks to SpecialTech for supplying the Alphacool NVXP-G8 8800GTS water block for review.

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