Friday, October 29, 2010

Corsair H70: Next-Gen Self-Contained Liquid Cooling

Liquid cooling still has the image of being expensive and complicated. Corsair, in cooperation with the cooling specialists at Asetek, now offers the H70 that aims to simplify the step up from air cooling. Can it beat less expensive premium heatsinks?
Liquid Cooling: Pros And Cons
Anyone familiar with the subject of liquid cooling knows that it can be quite a challenging topic with which to deal. What components do you need to buy? Should you buy individual parts or go for a pre-assembled system? Which manufacturer can you trust as you contemplate adding water inside your PC?

These are probably the most frequently asked questions when an enthusiast first contemplates entering the world of liquid cooling. However, things have changed in recent years. Last year, we looked at one of the first self-contained liquid cooling solutions, Corsair's H50, and found it to be comparable to some of the air coolers out there. That's not particularly ideal when you're trying to preach the benefits of liquid cooling. However, the device did successfully fit in environments where larger air coolers simply couldn't.
We now have the company's follow-on to the H50, called the H70, which again demonstrates that liquid cooling doesn't have to involve a complex setup procedure. But does it improve on the H50's performance?
H70: Prefab Liquid Cooling From Corsair
This is where the Corsair H70 liquid cooling system comes into play. It is designed to achieve high cooling performance, low noise levels, and simplify installation by as much as possible. Just like the previous model, the Corsair H50, the Corsair H70 is a complete closed loop cooling system consisting of a radiator, hoses, CPU water block, fan, and coolant, fully assembled from the factory. In addition to making the installation easier, this also saves you the trouble of gathering the necessary components yourself.
The Corsair H50 cooling system was the first result of cooperation between Corsair and the manufacturer Asetek, the company behind the CPU freezer Vapochill that let you operate your CPU at -20°C back in 2003. The challenge, here, of course, is trying to exceed the capabilities of today's greatest air coolers from a liquid-cooled circuit. This isn't something the H50 was really able to do, but our expectations of the improved H70 are naturally much higher.

The Corsair H70 prefab liquid cooling system comes in a sturdy cardboard box. In addition to the already-filled, closed loop cooling system consisting of radiator, hoses, and water block with built-in pump, we find detailed installation instructions and mounting hardware for different computer platforms in the package. The Corsair H70 supports Intel's LGA 775, 1366, 1156 interfaces, along with AMD's AM2 and AM3 sockets.
Additionally, the Corsair H70 cooling system includes two fans that operate at 2000 RPM. The included adapter cables with embedded resistors (~30 ohms) can be used to bring the fans down to 1600 RPM for quieter operation. There is no thermal compound included, which most coolers usually do bundle.
Compact Water Block
Instead, Corsair opts to cover the CPU water block base with a layer of thermal compound straight from the factory. This thermal compound is protected by a solid and easily removable plastic cap that is attached to the underside of the water block, protecting it from damage during transport.
Hardcore cooling enthusiasts would likely remove the compound and replace it with a thin layer of something more expensive, but obviously this is not mandatory.
With a height of just two inches, the water block is very compact. The low profile is even more notable when you consider that the pump is integrated with the water block, driving the coolant through the closed loop system. A cable connects the pump and the motherboard, supplying the pump with 12 V power. The pump is extremely quiet; only in a completely silent environment were we able to hear a faint hum.
Rigid Tubing
The coolant travels through the cooling system via two small and relatively rigid tubes. They have an outer diameter of about 8 mm and a length of about 24 cm. The tubes are attached to the pipes in such a secure way that they can only be replaced with great effort. Except for the water block, the loop also includes the radiator. Due to the short length of the cables, you might not be able to install the radiator exactly wherever you want to if you are using a large computer case.

Compact Radiator With Lots of Fine Fins
At a height of about 15 cm and a width of about 12 cm, you can easily install the radiator inside large-enough cases by attaching it to a 120 mm fan ventilation hole. The depth of the radiator is 5 cm--twice as thick as on the Corsair H50 model. If you use both of the included fans by sandwiching the radiator in a push/pull configuration, you get a total thickness of 10 cm, which could become a problem in more compact cases.
The radiator's fins are quite dense, spaced just 1 mm apart. On the one hand, this provides for a high number of fins, creating a large surface area for heat transfer. On the other hand, this also restricts air flow, so you should definitely use both fans in order for the radiator to work at maximum effectiveness.
As mentioned before, these fans rotate at 2000 RPM, but can be slowed down to 1600 RPM with the included resistor cables. This is necessary if you are aiming for a relatively low-noise kind of setup. The fans have rather short cables, at just 21 cm each. Depending on where in your computer case you install the radiator and where on your motherboard the fan connectors are placed, this might pose a problem.
Installing this liquid cooling system is fairly easy, although you might need to think things through when fastening the water block to the motherboard. You need to use the appropriate mounting hardware that fits your motherboard. Installation instructions are included to help you choose the right one. For our LGA 775 system, we first had to attach four risers on the water block back plate that goes on the rear side of the motherboard, which the screws are fit into later.
You also need to fasten a plastic mounting bracket on the front of the motherboard, and you should take a close look at the instructions so you do not choose the wrong one, as the included mounting bracket fastening parts are confusingly similar.
When the preparations are complete, everything goes quickly. Attach the back plate to the motherboard, then the mounting bracket, and finally put the water block on top of the CPU. With a twist to the right, the water block is securely fastened to the mounting bracket. The final step is to tighten the screws, preferably in a diagonal order so that you do not put too much stress on just one side of the CPU and socket.
Fan Configuration
The radiator can be installed pretty much wherever you want it--within the boundaries set by the length of the tubes, of course. A good choice seems to be in the back of the computer case.
The two fans included provide for a couple of different configuration options. Corsair recommends attaching them both to the radiator in order to achieve maximum cooling performance, but you also have to decide whether you want to have them suck in cool air from outside the case through the radiator, or blow out hot air from inside the case through the radiator. Here you have to take into account maximum CPU cooling versus the risk of heat accumulating inside the case and making the rest of your components warmer. You probably need to play around a bit with this to see what fits your case and fan setup the best.
Also, remember to balance the number of fans sucking air in and fans blowing air out, as axial fans of the kind used in computer cases are less effective when working against large differences in air pressure.

Test System
To ensure test score compatibility with the air cooling products already tested, we reviewed the Corsair H70 liquid cooling system using the same old, proven test system. At its heart, we find an Intel Pentium D840 Extreme Edition CPU with a Smithfield core, manufactured using 90 nm technology and employing a factory clock speed 3.2 GHz. The TDP (Thermal Design Power) is 130 W (the same as an Intel Core i7 CPU based on the Bloomfield core).
The Intel Pentium D840 Extreme Edition CPU is far more inefficient than the current Intel Core i7, of course. But then again, we are measuring temperatures here, not performance. To quite literally turn the heat up some more the CPU is overclocked to 3.6 GHz. Also, we use the thermal compound applied to the water block at the factory.
The ambient temperature was 21° C. Further test system details can be found in the table below.
System Hardware
Intel Platform (LGA 775)Gigabyte GA-G33-DS3R, Intel G33, BIOS: F5 (09/07/07)
CPUIntel Pentium D 840 Extreme Edition (90 nm SmithField core) @ 3.60 GHz
RAM4 x 512MB Samsung M3 78T6553CZ3-CE6 DDR2-667
System Hard DriveHitachi Deskstar 7K250, 160 GB, 7200 RPM, SATA 1.5Gb/s, 8 MB Cache
DVD-ROMSamsung SH-D163B, SATA 1.5Gb/s
Graphics CardIntel GMA 3100 Onboard
Network CardRealtek RTL8168/8111 PCIe Gigabit Ethernet NIC
Sound CardIntegrated
PSUSilverStone SST-ST50EF, 500 Watt
System Software
OSWindows Vista Enterprise SP1
DirectX 10DirectX 10 (Vista Standard)
DirectX 9Version: April 2007
Graphic DriversVersion 6.0.6000.16386 (Vista Standard)
Network Drivers9.0.32.3 (Vista Standard)
Intel Chipset DriversVersion (05/02/2007)
JMicron Chipset DriversVersion (24/03/2007)

Fan Configuration and Speed Control

As mentioned, the Corsair H70 comes with two fans. For our tests, we fit the radiator with only one, and then both fans. The fans only have 3-pin connectors, and therefore cannot be controlled via the pulse width modulation (PWM) features offered by many newer motherboards. However, the motherboard we used for the test had a BIOS setting for automatically controlling the voltage supplied to the fans. We used this setting both with one and two fans, and in the graphs on the following pages this is referred to as “Auto”.
The BIOS did not have a way of manually setting the fans to high or low, however, so we turned off the feature for those tests. Instead we used the included resistor cables to operate the fans at Low speed. For the High speed tests we simply ran the fans with neither resistor cables nor BIOS settings--au naturelle.

The idle temperatures were measured about 30 minutes after booting up Windows Vista. In these 30 minutes the CPU was just idling, and all services that might put a load on the CPU were turned off. The load tests were conducted using Prime95, measuring the maximum temperature after that time frame.
Fan Speeds
Noise Levels
Not surprisingly, the temperature using two fans without any speed limits was the lowest one. The temperature reported was 21° C, the same as the room temperature. The drawback, of course, is that the fans spin at just under 2000 RPM, resulting in a loud background noise measured at 57.3 dB(A). The fan speeds and noise level are the same under full load as well, keeping the CPU at a relatively low 38° C.
The weakest cooling performance is realized (not surprisingly) when using only one fan with the help of the motherboard BIOS fan controller. Here a temperature of 25° C is reached in idle mode, which increased to 47° C under full load. The noise levels in this configuration are 41.2 dB(A) in idle mode and an audible 47.9 dB(A) under full load.
The most balanced mix between cooling performance and noise levels is achieved when using two fans that are regulated by the automatic fan controller on the motherboard. This results in a very low 22° C temperature in idle mode with a moderate noise level of 37.9 dB(A). We also find the temperature of 41° C at full load acceptable, as is the noise level of 45.6 dB(A).

Note: Heat sinks that ship without any included fans were equipped with a standard fan from the 3RSystem Iceage Prima Boss. It has performs similar to a NoiseBlocker Multiframe M12PS.
The Corsair H70 liquid cooling system scores a low 38° C with the fans set to high, about the same temperature as the air CPU coolers Prolimatech Megahalems (Rev. B), or the Zalman CNPS 10X Extreme, and is thus placed pretty high up on the chart.
In our preferred configuration with two fans and automatic motherboard fan control, the Corsair H70 is at about the same level as a Noctua NH-D14--at least in terms of cooling performance. In this chart, the all-in-one liquid cooling system is definitely up there at the top. However, looking at the noise level chart at the next page, things get a bit complicated.

Even in idle mode, the Corsair H70 liquid cooling system is not among the quietest CPU coolers. The most acceptable values are reached with two fans and automatic fan control, and the other configurations show that using this system will not exactly make your computer system a very quiet one.

Under full load the picture changes a little, but even here Corsair H70 is nowhere near the top of the chart.

With the H70, Corsair brings a liquid cooling system to market that strives to address the challenges of liquid cooling while still exemplifying its benefits.
It relieves the user of the hassle of having to assemble individual components, which should appeal to those without much experience in liquid cooling. With a street price of around $110, it is reasonably priced compared to other liquid cooling systems. By pre-filling the closed loop system at the factory, it is ready for use immediately after unpacking, and does not have to be much more complicated to install than some air CPU coolers.
In addition, Corsair offers a two-year warranty, and the producer Asetek indicates that the average lifespan of the liquid cooling system is about 50 000 hours. Installing the liquid cooling system is easy, and the detailed installation instructions for the different supported processor interfaces should simplify the process for less experienced users.

There are a few weak points, however. We would have liked the tubing between the water block and the radiator to be a bit longer than 24 cm. The same goes for the fan cables, which are a bit short at just 21 cm. The fans included created mixed impressions. On the one hand, the radiator with its very dense fin structure requires a certain air throughput--something the fans handle just fine. But on the other hand, these fans are not exactly the most acoustically-friendly. Quieter fans with variable speeds would be something to hope for here. You could look around for alternatives, but then you'd only be adding to the cost of this unit, which already exceeds the upper range of the highest-end air coolers.
However, if you can live with the slightly elevated background noise level that comes with the Corsair H70 liquid cooling system, you get cooling performance in the good to very good range in the upper segment of CPU coolers.
In the light of air cooling alternatives like Zalman’s CNPS 10X Extreme, which costs roughly $69, Corsair’s new H70 remains a premium-priced product. It's perhaps best suited to environments where space around the processor is tight, and you don't have room for a cheaper, comparable-performing high-end air cooler.


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