Alphacool OTC Flat 8800 Water Block 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!

Alphacool website image
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 site, through to the updated product lines, Alphacool is on a mission!

Today I have been given the opportunity to review the new Alphacool OTC Flat 8800 full-cover water block. During the performance review today the Alphacool OTC Flat  will be going head-to-head with another full-cover water block - the EK FC8800 GTS.

Alphacool OTC Flat

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


Flowrate: 3.4 to 3.5 L/m (204 to 210 L/h)
               4.8 to 4.9 L/m (288 to 294 L/h)

Connections: G 1/4"

Dimensions: 178 x 118 x 4 mm (21mm including connections)

Weight: 0.555kg

The OTC Flat's specifications certainly look good on paper, however, there are 2 areas that really stand out. Firstly, the OTC Flat weighs in at a mere 555 grams. That is one lightweight water block especially when compared to the 800 gram NVXP-G8.

Secondly, the OTC Flat boasts an incredible 4mm thickness which is great if you decide to have 2 of them cooling an SLI setup.

However, according to the supporting literature, it looks as if the OTC Flat really suffers when it comes to overall flow rates. I guess we'll just have to wait and see when it comes time to test.

Let's head over the page and have a closer look at the Alphacool OTC Flat water block to see what you get for your money...

Alphacool OTC Flat 8800 Water Block Page: 2
Packaging and Contents

When I received the new Alphacool OTC Flat 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, and mine when it arrived was badly cracked. As a result I have decided not to include an image of the packaging. 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.

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.

Alphacool new packaging
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 Alphacool OTC Flat, so bear this in mind. I have included my personal favourites, the EK hi-flow 1/2".
Alphacool OTC Flat package contents

Included in the packaging are the following items:

* 1 x Alphacool OTC Flat 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 OTC Flat is very stylish to say the least.
Alphacool OTC Flat Alphacool OTC Flat reverse
Alphacool OTC Flat Alphacool OTC Flat

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. The base appears to have been finished with 'glass balling' to ensure maximum thermal transfer between the graphics card and the water block itself.
Thickness of the water block
At a mere 4mm I still can't believe how thin the Alphacool OTC Flat really is.
Alphacool OTC Flat image showing thickness Thickness again

Unlike the Alphacool NVXP-G8 the Alphacool OTC Flat doesn't restrict you to having the inlet and outlet in one static position only. Whilst the OTC Flat still isn't as configurable as the EK water blocks, it certainly is a step in the right direction. SLI enthusiasts may have another choice for water-cooling now! 
Inlet/Outlet configuration Inlet/Outlet removed
 Inlet and outlet channels Barb direction changed
Changing the direction of the barbs is an absolute cinch. Simply undo the 3 Allen Key screws and change the direction of the barb recepticle and the blanking plate, ensuring that the 'O-rings' are reseated properly, and then tighten. Voila...easy peasy. 
Naked NVIDIA 8800GTS Alphacool OTC Flat installed
Alphacool OTC Flat installed side shot
Installation of the Alphacool OTC Flat was very quick indeed. Faster than the EK FC8800GTS, in fact!
Let's head over the page to see how we're going to test the Alphacool OTC Flat...

Alphacool OTC Flat 8800 Water Block Page: 3
Testing Methodology

For the testing phase of the review I have chosen to test the Alphacool OTC Flat 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 OTC Flat 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 OTC Flat 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

Variable PSU Pressure drop testing
EK FC8800GTS 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.

Assessing flow

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 OTC Flat water block would perform in your system. The Alphacool OTC Flat'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 OTC Flat 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 Q6600 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 OTC Flat 8800 Water Block Page: 4


You can see from the graph below that there is quite a considerable pressure drop for the EK FC8800 GTS water block, but yet, the Alphacool OTC Flat causes the least amount of loss. Subsequently, the Alphacool OTC Flat takes first place.

Head Pressure Loss chart

The Alphacool OTC Flat proved to be the most restrictive block of the two tested, with the EK FC8800GTS facilitating considerably more flow 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 test Graph

You can see from the graph below that the Alphacool OTC Flat suffers a little when compared to the EK FC8800GTS. The Alphacool OTC Flat provided consistently higher temperatures at idle, load and also when overclocked even when you account for the slightly elevated ambient temperature. The OTC Flat also didn't allow us to see the full potential of the 8800GTS graphics card, by falling slightly short and allowing a 650 Core/1009 Memory overclock.

 Alphacool OTC Flat Temps

Ambient Temperature - 26.2 Deg C

Water Temperature

Idle         Load        Overclocked
33.2 Deg C34.1 Deg C35.3 Deg C

EK FC8800GTS temps

Ambient Temperature - 24.6 Deg C

Water Temperature
Idle  Load Overclocked
31.4 Deg C32.3 Deg C33.5 Deg C

Subsequently, the Alphacool OTC Flat gets beaten by the EK FC8800GTS water block in todays performance review. However, in the Alphacool's defence it is an extremely good looking water block and if you weren't looking for the best performance and had a decent pump to counter the restriction,  then it would certainly be a suitable addition.

Let's head over the page to see a summary of the Alphacool OTC Flat's performance today...

Alphacool OTC Flat 8800 Water Block Page: 5
Final Thoughts and Conclusion

So how did the Alphacool OTC Flat perform in our review today?

Well the Alphacool OTC Flat 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. I must admit that I really love the thin profile of the water block, and the black textured top makes a nice change from clear perspex or black Acetal. 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. As evidenced by our broken packaging today.

Alphacool OTC Flat water block

Looking at the Alphacool OTC Flat's performance today there are a couple of areas that need further discussion. The decision to run with what is a phenomenally thin water block, has led to a huge amount of flow restriction. So much restriction, in fact, that I cannot recommend the Alphacool OTC Flat for dual graphic card purposes, but merely as a single card alternative. However, the Alphacool OTC Flat facilitated less pressure-drop than the EK water block.The EK FC8800GTS on the other hand still maintained the better flow-rate, and can certainly be utilised in dual-graphics card setups.

Secondly we can see again that the included thermal pads don't transfer heat as efficiently as regular thermal paste. The EK FC8800GTS again wins the memory overclocking stakes, simply because the thermal paste transfers heat more effectively.  Furthermore; the more efficient EK FC8800GTS was also able to take my GPU's core clock from the default of 513Mhz to 663Mhz. Whilst the Alphacool OTC Flat provided more than acceptable temperatures across the board in todays review, it has been beaten quite soundly by the well rounded EK.

The Alphacool OTC Flat can be purchased from SpecialTech for around £ 54.99, inc VAT 17.5%, whereas the EK FC8800GTS comes in at a couple of quid cheaper and it is the better performer. If you are a dedicated Alphacool fan and aren't looking for the best performing full-cover water block about, then the Alphacool OTC Flat may appeal.

Let's have a look at the breakdown:

The Good
• Gorgeous looks
• Alphacool quality
• Barb configuration can be changed (up or down)
• Acceptable cooling
• Little pressure-drop
• Wafer thin and lightweight

The Mediocre
• Thermal pads perform less effectively
• Pricing when compared to the better performing EK FC8800GTS

The Bad
• Very restrictive

In conclusion, I have decided to award the Alphacool OTC Flat water block the Overclock3D 'Reviewed Award'.

Overclock3D Reviewed Award

Overclock3D would like to extend a thank you to Ayd at SpecialTech for supplying the review item.

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