Corsair Hydro Series H70 CPU Cooler Review

Although there were previous entries in the field, Corsair's Hydro Series H50 all-in-one sealed liquid cooling system was one of the first that actually worked, in the sense of being easy to install, reliable, and most importantly offering performance competitive with good air coolers while being quieter than most of them. The H50 became very popular and spurred competition from other vendors. The Corsair Hydro Series H70 improves upon the H50 design with a new pump and a much thicker radiator equipped with dual fans. It should offer significantly better performance than the H50, and Benchmark Reviews puts it to the test against a collection of air and water coolers to see how it compares.

Since all retail CPUs are boxed with perfectly good coolers (which are pretty quiet), the main reason to buy an aftermarket cooler is its performance when your processor is overclocked. (There might be some who buy coolers based on the aesthetics of their appearance through a windowed CPU case, but we'll assume they're in the minority.) But while performance is certainly the main criterion, other factors must be taken into consideration as well, such as noise, size, and price. The ideal cooler keeps your processor at or near ambient temperature, is silent, free, and unfortunately doesn't exist. Manufacturers vary the performance, noise, size, and cost factors of their products to address different segments of the market.

Corsair made their reputation in the enthusiast market with their memory products, which offered excellent performance and impressive visuals (who else sells colored accessory fins for their memory modules?), and has begun branching out into other areas with some notable successes such as the original Hydro Series H50 and the award-winning Obsidian 800D case. They also sell power supplies and USB and SSD drives.

Manufacturer: Corsair
Product Name: Hydro Series H70
Model Number: CWCH70
Price As Tested:$109.99 at Newegg

Full Disclosure: The product sample used in this article has been provided by Corsair.

Corsair H70 Specifications

Closer Look: Corsair CWCH70

The Corsair Hydro Series H70 comes in a rather large box. You know you're buying something impressive, even if exactly what it is isn't immediately obvious.

Inside the box are the neatly arranged components...

...which are the pump and radiator assembly, two 120x25mm fans, a manual, an installation instruction sheet, and mounting brackets and screws. The H70 comes with everything you'll need for Intel Socket 775, 1155/1156, 1366, and AMD sockets AM2/AM2+/AM3. Also included are a 3-pin "Y"-cable that allows you to run both fans off a single motherboard header, and two "step-down" resistor cables that drop the fan RPM from 2000 to 1600.

The H70 is different from its H50 predecessor in several ways: the radiator is twice as thick, there are two fans instead of one, and the pump unit is smaller. A lot smaller, really: compare the H70 pump (on the left) to the H50 pump (on the right). You might wonder if the newer, smaller pump has the same flow rate as the older, larger pump, but since neither Corsair nor OEM Asetek (who manufactures the H70 for Corsair) publish this information, there's no way to know.

The H70 retains the same mounting mechanism as the H50: a thin metal retaining ring with interior notches is secured to a back plate by four screws. The pump has notched edges; after mounting the bracket and installing the screws part-way, you insert the pump from the top and rotate it a few degrees so that the notches on the edge of the pump slide under the notches on the inside of the retaining ring. Tightening the screws will clamp the retaining ring against the pump and press it firmly against the processor. You'll actually have to assemble a bespoke bracket from the components included: four metal screw inserts must be positioned in the correct 4 (out of 12) possible places in the Intel back plate, and the retaining ring requires that 4 screws be inserted into the proper plastic offsets, which are then snapped into the retaining ring. All told, 14 different pieces comprise a complete mounting system, and paying attention and assembling the right parts correctly for your application will pay off.

The original Asetek water coolers used a much more robust mounting system. Compare the older mounting system on the left, which uses a 1/8" steel base plate and a thick plastic retaining ring secured by compression screws, with the current mounting system that uses a plastic base plate and thin sheet metal retaining ring, the "springiness" of which provides the clamping pressure. Clamping pressure is an important part of overall heat sink performance, and the best performing air coolers like the Polimatech Megahalems and Thermalright Venomous X have very substantial mounting systems.

I suspect the older mechanism provides higher clamping pressure that might improve performance, but the side-mounted swivel hose fittings on the H70 pump mean that a little Dremel work would be required to find out.

Corsair CWCH70 Detailed Features

The H70's pump is much smaller than the pump used in the H50, and has another welcome feature: swivel attachments for the hoses, which makes arranging things inside your case somewhat easier. This image shows the pump unit with its plastic protective cap, which you'd remove before installing it.

Even with the swivel fittings, the pump and radiator assembly is unwieldy. The hoses are short and much stiffer than you'd expect. The hoses, pump, and radiator are all permanently attached to each other.

The base of the H70's pump comes with pre-applied thermal compound, but our testing regimen requires that we use the same thermal compound for all heat sinks. Removing the included compound reveals a base that's flat, with a pronounced texture. This finish is common to all the Asetek-derived water cooling systems I've seem from various manufacturers, and the H70 is a Corsair-labeled version of Asetek's 570LC liquid cooling system.

The thicker radiator, with both fans installed, will take up quite a bit of room in your case. The width of the entire assembly is exactly 3 7/8", and the fans are installed in a "push-pull" arrangement. Corsair recommends that they be oriented so that cool air from outside the case is pulled through the radiator into the case. Corsair H50 owners have added dual fans to their single-fan systems since the the day H50 was introduced, and Corsair even has a configuration guide on this very subject.

Reading the H70's installation instructions will pay off. I didn't, and installed the radiator/fan assembly first. As this picture of the mounted assembly shows, doing so will leave you unable to reach the rearmost two screws that secure the pump retaining ring. Corsair rates the original H50's fan at "about 50CFM"; assuming the two H70 fans are similar to the H50 fan, that means that if you follow Corsair's instructions, you'll have up to 100CFM of hot hair being blown intoyour rig's case. If you have one or two high-end video cards you might want to experiment with orienting the fans to blow air out of the case.

Installing the unit is a little clumsy: first, you must support the radiator/fan assembly while installing the pump, and the relatively short hoses mean that you can't hang it outside the case. And once you have the pump secured, securing the radiator/fan assembly is even trickier: while the inside fan can be pre-mounted to the radiator, the outside fan cannot. You must thread a long screw through the back of your case, through the rear fan, and into a screw hole on the radiator. This is hard to do since you must precisely position the large and relatively heavy assembly while the "springiness" of the water hoses is working against you. A second person helping to support the radiator/fan assembly can make the whole process much easier. And with the cooler is installed, it's time to start the testing.

Heatsink Test Methodology

Benchmark Reviews is obsessed with testing CPU coolers, as our Cooling Section has demonstrated over the past few years. We've solicited suggestions from the enthusiast community, and received guidance from some of the most technical overclockers on the planet. As a result, our testing methodology has changed with every new edition of our Best CPU Cooler Performance series. Because of this, each article is really its own stand-alone product, and cannot be fairly compared to the others. Benchmark Reviews continues to test CPU coolers using the stock included fan (whenever applicable), and then replace it with a high-output fan for re-testing.

Manufacturers are not expected to enjoy this sort of comparison, since we level the playing field for all heat sinks by replacing their included fan with a common unit which is then used for every CPU cooler tested. Many manufacturers include fans with their heat sink products, but many 'stock' fans are high-RPM units that offer great airflow at the expense of obnoxiously loud noise levels, or, conversely, quiet fans that sacrifice performance for low noise. By using the same model of cooling fan throughout our heat sink tests, we can assure our results are comparable across the board. This is one of the more significant changes we have made to our test methodology, since many of the benchmark tests we have conducted in the past have compared the total package. Ultimately we're more interested in the discovering the best possible heat sink, and we believe that you'll feel the same way.

For each test, ambient room temperature levels were maintained within one degree of fluctuation, and measured at static points beside the test equipment with a digital thermometer. The Corsair H70 and the comparison coolers used a common Thermal Interface Material of our choosing (listed in the support equipment section below) for consistency. The processor received the same amount of thermal paste in every test, which covered the heat spreader with a thin nearly-transparent layer. The heat sink being tested was then laid down flat onto the CPU, and compressed to the motherboard using the supplied retaining mechanism. If the mounting mechanism used only two points of force, they were tightened in alternation; standard clip-style mounting with four securing points were compressed using the cross-over method. Once installed, the system was tested for a baseline reading prior to testing.

At the start of each test, the ambient room temperature was measured to track any fluctuation throughout the testing period. AIDA64 Extreme Edition is utilized to create 100% CPU-core loads and measure each individual processor core temperature. It's important to note that software-based temperature reading reflects the thermal output as reported from the CPU to the BIOS. For this reason, it is critically important (for us) to use the exact same software and BIOS versions throughout the entire test cycle, or the results will be incomparable. All of the units compared in our results were tested on the same motherboard using the same BIOS and software, with only the CPU-cooler product changing in each test. These readings are neither absolute nor calibrated, since every BIOS is programmed differently. Nevertheless, all results are still comparable and relative to each products in our test bed (see The Accuracy Myth section below).

Since our test processor reports core temperatures as a whole number and not in fractions, all test results utilize ADIA64 to report averages (within the statistics panel), which gives us more precise readings. The ambient room temperature levels were all recorded and accurate to one-tenth of a degree Celsius at the time of data collection.

When each cooler is tested, Benchmark Reviews makes certain to keep the hardware settings identical across the test platform. This enables us to clearly compare the performance of each product under identical conditions. Benchmark Reviews reports the thermal difference; for the purposes of this article, thermal difference (not the same as thermal delta) is calculated by subtracting the ambient room temperature from the recorded CPU temperature.

Please keep in mind that that these test results are only valid within the context of this particular test: as the saying goes, your mileage may vary.

Intel Test System

• Processor: Intel Core i7-950 Bloomfield 3.06GHz LGA1366 130W Quad-Core Processor Model BX80601950, core voltage set to 1.35V
• Motherboard: ASUS Sabertooth X58 Intel X58-Express chipset) with BIOS 0603, BCLK set to 175MHz for a processor speed of 4025MHz

Support Equipment

• AIDA64 Extreme Edition version 1.50.1200
• MG Chemicals Heat Transfer Compound 8610-60G
• Stock fan (for heat sinks without fans): Thermalright TR-FDB-12-1600 (63.7CFM advertised)
• High-speed fan: Delta AFC1212D (113CFM advertised)

All of the tests in this article have been conducted using vertical motherboard orientation, positioned upright in a traditional tower computer case. Air-cooled heat sinks are positioned so that heatpipe rods span horizontally, with the fan blowing air out the top of the chassis. The radiators of water coolers are mounted as per manufacturer instructions. In both cases, fans are connected directly to the power supply (rather than motherboard headers) and run at full speed during the test. At the start of our test period, the test system is powered on and AIDA64 system stability tests are started with Stress CPU and Stress FPU options selected. AIDA64 loads each CPU core to 100% usage, which drives the temperature to its highest point. Finally, once temperatures have sustained a plateau (no observed change in average temperatures for 5 minutes), the ending ambient room temperature and individual CPU core levels are recorded thus completing the first benchmark segment. The time to reach stable temperatures varied between 10 and 20 minutes for the heat sinks in this test; larger heat sinks typically take longer to stabilize.

The second test segment involves removing the stock cooling fan and replacing it with a high-output 120 mm Delta AFC1212D cooling fan, then running the same tests again.

Note: The Coolit Vantage A.L.C. is designed to drive its own PWM-controlled fan directly, and an alarm will sound continuously if the fan is disconnected. Since I don't believe anyone would ever run the cooler this way, I left the fan connected to the cooler (with the cooler set to "Extreme" mode) for stock fan testing. For high speed fan testing, I connected the Delta fan directly to the power supply, and ignored the alarm.

The Accuracy Myth

All modern processors incorporate an internal thermal diode that can be read by the motherboards' BIOS. While this diode and the motherboard are not calibrated and therefore may not display the actual true temperature, the degree of accuracy is constant. This means that if the diode reports 40°C when it's actually 43°C, then it will also report 60°C when it's truly 63°C. Since the design goal of any thermal solution is to keep the CPU core within allowable temperatures, a processor's internal diode is the most valid means of comparison between different heat sinks, or thermal compounds. The diode and motherboard may be incorrect by a small margin in relation to an actual calibrated temperature sensor, but they will be consistent in their margin of error every time.

Testing and Results

For this test, I used the following heat sinks in addition to the Thermaltake Jing:

• Thermalright Venomous X
• Cooler Master V6 GT
• Prolimatech Super Mega
• Corsair Hydro Series H50
• Corsair Hydro Series H70
• Coolit ECO A.L.C.
• Coolit Vantage A.L.C.

For heat sinks without a stock fan, I used a Thermalright TR-FDB-12-1600 fan, which puts out 63.7CFM at 28dBa according to Thermalright. This mid-range fan provides good air flow and reasonable noise levels. For "apples to apples" testing, where each heat sink is tested with the same fan, I used a Delta AFC1212D. This high-performance PWM fan is rated at 113CFM at a claimed 46.5dBa at full speed...which means that while it moves quite a bit of air, it's very loud.

The Intel Core i7-950 I used in this test runs much hotter than the Core i7-920 I'd used previously. At 1.35 volts, with a BCLK of 175Mhz, the 4,025Mhz CPU pumped out enough heat to stress the very best heat sinks. AIDA64 would report throttling once any single core reached 100 degrees Celsius; any throttling resulted in cancelling the test and recording a "FAIL". Although this overclocked and overvolted Core i7-950 represents an extreme, these are expensive, high-end heat sinks.

The chart below summarizes the results with the stock fans (hotter temperatures towards the top of the chart, and cooler temperatures towards the bottom). The twin-fan units (the Cooler Master V6 GT and the Corsair H70) have a real advantage here, since their dual fans move more air than the stock single fan of any of the other units. The Corsair H70's fans at their default 2,000RPM level move a lot of air together, but also generate a fair amount of noise. At the 1,600RPM level achieved with the in-line resistor cables, the noise level is much reduced, with a relatively minor performance hit. While Corsair says the stock H50 fan provides about 50CFM, they do not provide any specifications on the H70 fans other than their dimensions, so the official air flow, static pressure, and noise levels are a mystery, which is annoying if you are considering replacing the fans.

Stock Fan Tests

With its dual, high performance fans (according to Cooler Master, each fan is rated at 93CFM at full speed, for an aggregate airflow of over 180CFM) the Cooler Master V6 GT takes the lead here, keeping the blistering hot Core i7-950 4.1 degrees Celsius cooler than the H70 with its fans running at full speed. The Cooler Master H70 also benefits from dual fans, but perhaps they're not moving quite as much are as the V6 GT fans (we don't really know since Corsair does not provide airflow numbers). Dropping the H70's fan speed to 1,600RPM with the included resistor cables makes the system much quieter at the cost of 2.4 extra degrees of processor temperature.

What's interesting in this chart is the 5.3-degree "break" between the Coolit Vantage A.L.C. and the Corsair H70, which neatly separates the coolers into "lower performance" and "higher performance" groups.

Delta High Speed Fan Tests

With the Delta high-speed fan, our lineup changes. The Coolit ECO A.L.C. moves from the bottom to the chart to just beyond mid-pack, improving by almost 11 degress. The Prolimatech Super Mega and Thermalright Venomous X jump to the to lead, and the Corsair H70 drops back a few places, although its actual performance is very slightly (0.6 degrees Celsius) better. This is something I've seen before when replacing a dual-fan cooler's stock fans with a single fan: the performance advantage of even very noisy, high speed fans is minimal if it exists at all. Note that in this scenario, the Coolit ECO A.L.C. with its much thinner radiator actually performs better than the H70. I think the 48mm-thick radiator of the H70 works best with dual fans to push the air through all those fins. (Again, it would be nice to know the air flow and static pressure specifications of the included fans.)

In this chart, there's a 4.8-degree "break" between the Coolit ECO A.L.C. and the Cooler Master V6 GT. In this "apples to apples" comparison, the three top-performing air coolers are obviously in a class of their own. While all-in-one water cooling kits are making progress, Big Air still has a significant advantage in this scenario.

CPU Cooler Final Thoughts

Although all-in-one water cooling kits existed years before Corsair introduced the H50 in June, 2009, the result of this Asetek/Corsair collaboration provided much better performance than previous efforts. While the H50 didn't compete with high-end air coolers, it provided a quiet alternative to mid-range coolers for mild overclocking, and you could enhance its performance significantly by adding a second fan.

Two of the best ways to increase a heat sink's performance are to increase the surface area of the "heat exchanger" (where heat is transferred to the air), and to move more air over the heat exchanger. Corsair adopted both tactics with the Hydro Series H70, doubling the thickness of the radiator and adding another fan. Doubling the radiator thickness gives the same surface area as would increasing the radiator size to 120x240mm, but the latter solution would severely restrict the number of cases the cooler could be used in.

The thicker radiator and dual fans increase the performance of the H70 tremendously, giving it a solid 7.8 degree lead over the H50 when compared with the stock fans, and a 3.4 degree lead when both are configured with the high-speed Delta fan. Since the pump assembly is obviously different, it's possible that the internal heat plate design has changed or that the pump has a higher flow rate, but if so, neither Asetek nor Corsair are saying.

In previous reviews I've noted how rapidly the CPU cooler market was advancing, with new designs and new performance benchmarks appearing so frequently that it was hard to keep up. We seem to be approaching an asymptote, though: the size of air coolers is reaching the constraints imposed by standard computer cases, and performance is leveling off. Since any retail CPU is shipped with a perfectly good CPU cooler in the box, you might think that the only reason to purchase an aftermarket cooler is performance. While this is certainly the primary consideration, there are others, such as acoustics (how loud the cooler is) and aesthetics (for windowed cases). Also, bear in mind that not every cooler works in every situation: top-performing air coolers tend to be both large and expensive, and are overkill for all but the hottest, most overclocked systems. There's room in the market for many different types of coolers, and the best solution for you is probably not the best solution for me.

While water coolers have improved since 2009, so have air coolers. For $109.99 at Newegg, the Corsair H70 is significantly more expensive than a Prolimatech Super Mega or Thermalright Venomous X, although equipping the latter two coolers with two high-performance fans would narrow the price gap.

Normally, our high-speed fan tests provide a good indication of relative cooler performance, but I think in this case the H70's thick radiator threw the results off a bit, since it probably requires a higher static pressure for good performance than do the air coolers. If you do replace the fans on this cooler, you should stick with the dual-fan configuration...but the stock fans on "low" provide an excellent balance of performance and noise in most cases.

Corsair Hydro Series H70 Conclusion

Please remember that these test results reflect our experience with each cooler on a specific motherboard, with a specific processor, BIOS revision, BCLK and voltage settings, and test programs. The results of this test cannot be directly compared to other tests since many factors will have changed.

Installing the Corsair H70 is relatively easy if you read the directions first and take your time. The "universal" Intel backplate (on AMD systems, the stock motherboard backplate is used) keeps the parts count (and price) down, but I prefer the more robust mounting system design of Asetek's original systems.

The performance of the Corsair H70 was very good, easily beating all the other water coolers in this test, although it was still outperformed by less expensive air coolers. Doubling the radiator thickness enables the H70 to double the surface area of its heat exchanger, which when aided by its dual fans provided a real increase in performance. I'd prefer to see PWM fans like the Cooler Master V6 GT uses, so the computer could control the fan speed. Having to plug in resistor cables to control fan speed seems a crude solution, especially at this price level.

The construction quality of the H70 was also very good: everything fit and worked correctly and the swivel mountings for the hoses pivoted freely. I have seen some water coolers arrive new in the box with bent or damaged fins, but the H70's radiator was pristine. I would prefer to see a more robust mounting system, though, since I think the clamping pressure might be a bit low with the current system.

The main reason to go with the H70 over a top-end air cooler is noise: while the V6 GT kept the processor 6.5 degrees cooler than did the H70 (with its fans on low), it did so at a substantial cost in noise. Also, if you transport your computer, the weight of a high end air cooler (all of which are two or more times heavier than Intel's recommended weight limit) can actually damage the motherboard if the computer is subjected to shocks; the tiny pump of the H70 is a featherweight in comparison to the kilogram or heavier weights of a dual-fan equipped Megahalems.

Cosmetically, the H70's rather dull, with all-black components and the Corsair label on the pump being the only adornment of any kind. While not everyone uses a windowed case, a little extra bling wouldn't hurt, especially in an era where even Intel puts LED lighting on their retail CPU coolers.

If you're interested in exploring water cooling, the Corsair Hydro Series H70 is a good introduction.

Pros:

+ Good performance/noise balance with fans on low speed
+ Included "Y" and resistor cables for fans
+ Easy entry into water cooling
+ No maintenance required

Cons:

- Outperformed by less expensive air coolers
- Installation can be a bit tricky, pump mounting brackets seem flimsy
- Standard installation dumps hot hair back inside your case
- Cannot expand the system with chipset or GPU coolers
- Specifications for pump, fans seem to be secrets

Ratings:

• Performance: 8.50
• Appearance: 8.25
• Construction: 9.25
• Functionality: 8.75
• Value: 7.75

Final Score: 8.5 out of 10.

Recommended: Benchmark Reviews Seal of Approval.

Is the Corsair Hydro H70 on your shopping list? We invite you to comment below or start a discussion in our Forum.

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