tx850v2The Corsair TX850V2 (CMPSU-850TXV2) power supply is an enthusiast model that we procured for use with the desktop gaming machine. The old AK-680 PSU had dual 12V 20A circuits which limited the use of advanced gaming grade video cards somewhat. The TX850V2 uses a single circuit to eliminate confusion about cables and loading.

The Corsair TX V2 series offers the TX650, TX750 and TX850V2. Having experienced many PSU failures in the past, we went for the highest capacity. The top model has adequate power and cables for a pair of single GPU cards in SLI or CFX configuration.

We noticed that the Corsair TX850V2 V2 is internally identical to the XFX PRO 850W, and the only differences between the 850W and the 750W models are the use of more powerful switching transistors and one additional Schottky rectifier in the 850W models.

The TX850V2 is the standard ATX, 86mm by 150mm at the back panel, to fit the standard ATX screw positions. The TX850V2 is 160mm long which is 20mm deeper than the standard ATX. The longer size allows for the use of a bigger 140mm fan as well as for bigger heat sinks etc. The TX850V2 substantially exceeds the capacity guidelines for the old ATX standard.

The TX850V2 uses a single 12V circuit with 70A of current capacity which is enough to start a small car. The available 12V capacity is almost double the old AK-680 we replaced. The difference between the two PSUs is stark.

There are 4 PCIe 6+2 pin cables to support 2-way SLI and CrossfireX configurations. There is also lots of SATA connectors and Molex connectors to hook up peripherals.

The TX850V2 is really a 12 V PSU and it simply uses DC-DC converters to fulfill the ATX requirements. This is a common design with better quality power supplies as it means lower marginal costs using mass produced modules that can be used across the industry. This design means maximum power is available for any application.

The TX850V2 features an industrial looking paint scheme. Using safety yellow/orange for the trim gives the impression of a safe design. Given the complete set of safety features this seems appropriate.


  • ATX 2.31
  • EPS12V 2.91
  • Yate Loon D14BH-12 140mm double ball bearing fan
  • single 12V rail with 70A capacity
  • sleeved cables
  • automatic input power configuration
  • 80 PLUS bronze
  • 5 year warranty
  • RoHS Compliant

The TX850V2 features complete protection. Over current (OCP), over voltage (OVP), over power (OPP), under voltage (UVP) and short-circuit (SCP, tested and working) protections.

Corsair CMPSU-850TXV2 ATX Power Supply
AC Input: 100V – 240V DC Output +3.3V +5V +12V -12V +5Vsb
Current: 8A Max Load 30A 30A 70A 0.5A 3.0A
Frequency: 50Hz – 60Hz Maximum Combined Wattage 150W 850W 10W 15W
Total Maximum Power: 850W


  • ATX 2.x 20+4 connector
  • Single ESP12V 4+4
  • 4x PCIe 6+2
  • 2x SATA strand with 4 connectors
  • 2x Molex strand with 4 connectors
  • Berg strand

The cable bundle is excellent with long cables to support larger EATX chassis. All of the cables are sleeved properly using a brained sheath. The connectors are also excellent and are easy to attach. The cables seemed to be ideal in length when the TX850V2 was installed in our Corsair Carbide 300R chassis.


The TX850V2 is a very strong performer that is well suited to a modern gaming machine. The cables are sleeved to make it easier to zip-tie cables so that air flow is unimpeded. Sleeves also protect cables from abrasion that can happen with fan vibration.

Even loaded near its rating did not bother the TX850V2 but the fan did run hard when loaded to maximum. Voltages were all far better than the ATX specifications require. Obviously heat is the limiting factor and if the TX850V2 overheats the safety shutdown will activate.

We consider the TX850V2 to be a solid choice for a gaming machine. The single rail for power means any configuration is well provided for. The PSU can connect up anything from an old Pentium machine on up to the latest greatest rig.

We selected the TX850V2 for its competitive value. It has all of the features needed for a leading edge gaming machine. Bests of all it has lots of 12V capacity. 70A of current is enough to start a small car.

The TX850V2 uses DC-DC converters for the 3.3V and 5V circuits to increase efficiency. This design is now very common with better quality power supplies. These are the same the type regulators found on motherboards and graphics cards.

The TX850V2 uses a very good quality set of components to provide excellent correction capacity. This is important with the grid voltage often swinging around depending on the load etc. Here grid voltage swings from about 105V to 123V with an average around 112V. PC power supplies all have to install filters to prevent high frequencies from leaking onto the grid so they are easily designed to handle a wide range of input voltages without the need for a switch.


The TX850V2 uses a 140 mm double ball bearing fan which is very quiet when the load is under 25% and only begins to become noticeable when the unit is loaded hard.  The Yate Loon D14BH-12 has a rating of 140 CFM for airflow and rated 48.5 dB A-weighted noise level. In the typical gaming chassis general fan noise is perfunctory with two extreme gaming video cards installed. Fan noise with a single card is extremely good.

The TX850V2 has thermal controller for the fan which generally leave the fan at a very low operating speed. Its only when the power draw exceeds 50% that we noted the fan start to spin up.


Our Corsair TX850V2 is rated for 850W at 50°C which is very realistic. A PC PSU runs hot so anything that is not rated at 40°C or more is not suitable. We use digital thermometers and these can continuously monitor temperatures. The TX850V2 is clearly designed for use in older style chassis that mount the PSU on the top rear.

The thermometer has showed the exhaust air from the TX850V2 to be between 35°C and 40°C depending on the load. This is typical in a gaming PC with lots of fans installed. Clearly the TX850V2 is a very good performer that delivers full power even in a warm environment.  The motherboard usually ranges from 25°C to 30°C and the PSU seems to be < 15°C above the ambient.

Even powering a pair of overclocked GTX 260s did not appreciably warm the TX850V2. The larger Yate Loon D14BH-12 140mm fan does spin up considerably with games as expected–the video cards spin up too. Fan noise was not as bad as the AMD CPU fan which has a reputation for being very noisy. Larger fans move air more efficiently which is helpful for demanding applications.

When we installed the TX850V2 in our Corsair 300R chassis we noted a significant reduction in the PSU exhaust temperatures. The 300R moves the PSU to the bottom rear and the motherboard is moved up. Loaded temperatures fell to between 25°C and 35°C. With the cooler room air being drawn into the PSU, the thermal load is reduced considerably. The lower operating temperatures also extend the service life. Capacitors are the usual mode of failure of PC PSU failures.


Using the onboard motherboard sensors. They are as good as the digital multimeter we have. The oscilloscope also shows the TX850V2 to be extremely clean and nicely centered on the target voltages.

3.3V (orange) 3.312V < 1%
5V (red) 5.035V < 1%
12V (yellow) 11.994V < 1%

Obviously the TX850V2 achieves precision far beyond the required specifications in the ATX manuals. Its clear that Corsair worked hard to design a quality power supply. Generally enthusiast power supplies are far beyond the old ATX requirements.


Testing the TX850V2 with the P4400 showed the PSU to have an excellent power factor above 99% at all loads. Power supplies all use a simple low pass filter to prevent RF leaking into the grid.


Connecting our handheld oscilloscope to the 12V line show ripple levels were so low we had to zoom in 3 times to see it. The ripple is well under 50mV which is excellent. Clearly excellent quality capacitors and MOSFET’s are needed to achieve such good ripple values. Our low cost oscilloscope costs under $100 and its ideal for PSU testing and general RF use. Agilent oscilloscopes cost over $25,000 and are intended for large engineering shops and are excessive for a PC gaming review.

TX850V2 power at 3200%

Even with 3200% zoom, the TX850V2 does not flinch. This level of quality is why we selected the TX850V2 for the workstation.


The TX850V2 provides 15W of standby power to be able to support USB hubs in the event a keyboard is connected to one. Many power supplies are very inefficient with the 5 V standby circuit. The TX850V2 manages about 75% on the 5V standby which is much better than most rivals. The front USB 3.0 ports are powered when the machine is powered down, so its possible to charge a mobile phone or MP3 player without powering up the machine.


The TX850V2 is also able to achieve the 1W standby when a matching motherboard is used. The M5A99FX supports the latest standards making it a good match.


The TX850V2 is certified 80 PLUS bronze. This means it must be 82% efficient at 20%, 50% and 80% loads. As the graph shows the TX850V2 is a very well designed and efficient model. The top curve shows 220V while the bottom shows 115V service.

The curve shows that the TX850V2, like all power supplies, is more efficient with 220V. Its also is most efficient at around 50% load which is also very typical.


Corsair provides a 5 year warranty on their TX series power supplies. This can be done due to the very high quality components used.

Because Corsair rated their PSU at 50°C  we are confident in the quality of the product. 50°C  is much more reflective of real world conditions. We would like to see the whole industry use 50°C as a standard for testing.

Most gaming machines run cooler due to good air flow, but many machines have few fans so the overall operating temperatures are higher.


Many PSU vendors claim that their model is 850W but these vendors include 3.3  and 5V capacity in duplicate. Corsair and other respectable vendors only state the important 12 V capacity which is what matters to a PC gaming rig. After all the 3.3V and 5V are drawn from the 12V line. This is why 12V matters.

Because Corsair only states the realistic power capacity, we strongly recommend them. This way when selecting a video card and when the power requirements are checked, the rating of the Corsair PSU will be consistent with the gaming video card requirements.

Corsair has earned a reputation for better quality power supplies. They are more expensive, but the value is stellar.


We have installed the TX850V2 into the Corsair Carbide 300R chassis. The PSU is bottom mounted right-side up so that the cable bundle easily fits the slot. The cables easily reached the various connections suggesting this PSU cable set was designed for a mid-tower chassis. The TX850V2 also fits the larger 750D which has more room for water cooling.

The M5A99FX motherboard has enough fan headers that Molex cables are not needed. Fan controllers are a popular option with machines that lack adequate motherboard headers.

We have a pair of GTX 260 video cards and that is the load we intended when considering PSU capacity. The extra capacity provides lots of room for overclocking. The GTX 400 series reinforced the expectation that graphics power consumption was still growing. It was not until 2012 when the GTX 600 series became available that power consumption started to ease. Our GTX 660 Ti uses less than 150W of power.


Assuming that the old AK-680 is 60-70% efficient and the TX850V2 is 85% efficient we can develop a table of savings at all power levels. Saving 100W of power load amounts to 438 kWh in savings assuming 24/7 operation.

The state of California has much higher electric costs compared to us (14 cents per kilowatt hour) and the payback period would be far shorter. Hawaii has brutal electric rates of around 32 cents per kilowatt hour magnifying the savings even more. The EU pays very high electric rates and and as rates get higher the payback time get shorter and shorter.

Power plants are expensive and sometimes hard to place. So power companies work with the EPA to develop solutions and over the decades the work has saved the need for hundreds of power plants. Consumers also benefit with reduced energy costs.


The TX850V2 has continued to deliver clean power after more than 2 years of service. Corsair has expanded the replacement RM series ranging from 450W to 1000W. This new range will replace several other series in addition to the TX. Older 80 PLUS bronze models now make up the low end of the market. Rising energy costs put some pressure towards upgrading, but this makes more sense with rates above 25 cents per kWh.


The TX850V2 has demonstrated excellent service. In 2014 new models with 80 PLUS platinum are now widely available at up to 1500W. Over time the EPA 80 PLUS program has exceed expectations in reducing the number of power plants needed for personal computers. The fan on the TX850V2 has continues to be quiet with the dynamic fan control, the load is low enough at idle to warrant the minimum fan power.

With 2 more power hungry video cards the load in the TX850V2 has varied considerably. The use of 3 yellow wires for even the 6-pin power means extreme cards are well provisioned. Our HD 6970 uses both 6-pin and 8-pin power with a maximum 250W power rating.


Intel introduced the Z170 chipset 2015 and we noticed some motherboards now have a pair of EPS12V connectors. The AXi series PSU come with a pair of EPS12V cables to be able to cope with the increased motherboard demands. The TX850V2 is still practical for a dual video card setup, the more extreme 3-way and 4-way boards are more demanding.

We noticed that older obsolete model power supplies are still widely available. Power supplies are durable and are usually only replaced when they fail. At least modular cable models are widely available.