Rightfully, there have been many requests for us to review medium-to-low wattage power supply units. This is more than reasonable, as the average home PC almost never requires a PSU with a maximum output greater than 550-600 Watts. On our end, it is a little difficult to source such units, both because there are few worthwhile models and because manufacturers are more eager to supply samples of their high-end/flagship models than they are their lower-end models. There are a number of assumptions one could make about why the manufacturers prefer to have only their top models reviewed, but we would rather stick to the facts.

One of the very few manufacturers that responded to our call for sub-500 Watt units and immediately dispatched a sample is Corsair. Corsair provided us with a CS450M, the modular 450W version of the CS series. The CS series is a low-to-mid tier power supply – not the cheapest series that Corsair currently offers, but still value-minded – aiming to combine good performance and a high value for money. On paper, the 80Plus Gold certified CS450M appears to be a good deal for the retail price of $80 including shipping. The specifications however rarely ever say anything about the true quality and performance of a PSU, which we will examine in the following pages.

Packaging and Bundle

Corsair supplies the CS450M in a relatively simple, serious cardboard box. It is smaller than the boxes of the higher end models and that is because there are no polystyrene foam pieces protecting the unit, only a bubble bag. The CS450M however is much lighter than a >1kW PSU and the box is sturdy, therefore it should provide enough protection during shipping. The sides and the back of the box are littered with the specifications and the features of the PSU.

The bundle is exactly as we expected it to be - basic but not overly so. Corsair supplies a simple manual, the typical AC power cable, four black screws, and a few cable ties with the CS450M. This is nothing special but it is not that bad, considering that some companies even skip the AC power cable with their low cost models.

The CS450M is a semi-modular PSU, with the ATX and the CPU EPS cables hardwired to the unit while the rest of the cables are modular. There are only four modular cables, two with SATA connectors, one with Molex connectors and one with a single PCI Express connector.  With the exception of the sleeved ATX cable, of the cables are "flat", ribbon-like, with black wires. 

External Appearance

When you are on a tight budget, aesthetics are of secondary importance, but they are rarely ever of no importance at all. Corsair realizes that and they kept the appearance of the CS450M relatively plain but aesthetically subtle. Perhaps even overly subtle, as almost everything on the CS450M is black. The steel chassis has been sprayed with a matte black paint, a standard round black finger guard stands above the black cooling fan and the cables are entirely black as well. Only the side stickers with the company and series logo intrude on the blackness of the CS450M.

Other than that, the CS450M is built inside a standard, ATX-compliant 140 mm steel chassis. A sticker with the electrical and safety specifications of the PSU can be seen at the top side of the chassis. There is virtually nothing of real importance at the rear of the chassis, only a basic on/off switch and an AC power cable receptacle. Four cable connectors for the modular cables can be found at the front of the chassis.

Internal Design

Yate Loon supplies the black 120 mm fan responsible for the cooling of the CS450M. It is a rather basic model, with a sleeve bearing engine and a maximum speed of 1,650 RPM. Considering the small power output and efficiency of the CS450M, this fan should never go anywhere near its maximum speed to maintain low operating temperatures.  

Corsair entrusted the CS450M to Great Wall, a Chinese OEM that we are not very accustomed to seeing. As a matter of fact, no other PSU that we have ever seen uses this particular platform, so either Corsair designed it themselves and Great Wall is just building the PSUs, or Great Wall is allowing Corsair to use it exclusively. It does not matter either way, as the quality and performance of the PSU are what actually matters to the consumer. As far as quality is concerned, CS450M is substantially better than we initially anticipated considering the retail price of the PSU.

The filtering stage is textbook, with four Y capacitors, two X capacitors and two filtering inductors. One of the X capacitors, the one at the back of the AC receptacle, is a little oddly placed, with wires connecting it to the PCB and the body of the capacitor glued on the back of the PCB itself. An effective but very crude solution to the space problem. A NTC thermistor blocks large inrush currents and a simple relay short-circuits it once its job is done. The primary capacitor of this particular unit is relatively small and the inrush current should not reach noteworthy value, but Corsair is using the same platform for many other products, including models nearly twice as powerful, with much higher capacitance.

The primary side heatsink holds the main rectifying bridge, the active PFC components and the primary inversion transistors. The PFC inductor is a sealed type, meaning that the naked large inductor has been replaced by a black plastic block. Theoretically, this could suppress the generation of "coil-whine" noise problems, as that high frequency sound originates from the high frequency vibrations of the inductors under electromechanical stress. Surprisingly, the primary PFC capacitor is supplied by Rubycon and is rated at 400V/390μF. Rubycon is one of the most reputable capacitor manufacturers and we rarely see their products used outside premium products, so finding one in the CM450M is, mildly put, unexpected.

Meanwhile the secondary conversion transistors generate the 12V line, while the 3.3V/5V lines are being derived from it using DC-to-DC conversion circuits. A small transformer is present for the generation of the 5VSB line as well. The secondary capacitors are a very complex mixture of electrolytic and polymer capacitors alike. The electrolytic capacitors are supplied by Nippon Chemi-Con, Teapo and CapXon, while the polymer capacitors are a mix of Teapo and Chinsan products.

Cold Test Results

For the testing of PSUs, we are using high precision electronic loads with a maximum power draw of 2700 Watts, a Rigol DS5042M 40 MHz oscilloscope, an Extech 380803 power analyzer, two high precision UNI-T UT-325 digital thermometers, an Extech HD600 SPL meter, a self-designed hotbox and various other bits and parts. For a thorough explanation of our testing methodology and more details on our equipment, please refer to our How We Test PSUs - 2014 Pipeline post.

The Corsair CM450M makes a borderline pass through our efficiency test, just meeting the standards required for 80Plus Gold certification. The energy conversion efficiency reaches 92.1% at 50% load. An average conversion efficiency of 90.2% is achieved within the nominal load range (20% to 100% of the unit's capacity). It seemingly does not perform very well at very low loads, with a conversion efficiency of just 76.1% at 5% load. That however corresponds to an actual load of just 23 Watts and more powerful units would likely fare far worse at so low a load. With a load of 45 Watts, a fairly reasonable figure for the idling state of an average home PC, the conversion efficiency jumps to 83.5%.

As the power output of the CM450M is low and the conversion efficiency is high, it does not have high cooling requirements. Our testing results are not surprising, as the little 450W PSU maintains very low operating temperatures even when heavily loaded. The cooling fan does remain inaudible across most of the load range but it increases its speed at higher loads, reaching audible (but not intrusive) figures. 

Hot Test Results

Going by the results presented in the following tables, the Corsair CM450M offers good power quality. It is not going to break performance records but the CM450M performed well considering its price range. The maximum ripple on the 12 V line was 72 mV at 100% load, a good figure considering both that the design limit is at 120 mV and that this is a unit rated for operation at 40°C. The same goes for the 3.3V/5V lines, which reached a maximum ripple of 30 mV and 34 mV correspondingly. Voltage regulation is fair, at 2% for the 12V line and just a little higher for the 3.3V/5V lines.

Once again, we need to mention that this is a PSU rated at 40°C and we perform our testing at temperatures higher than 45°C - we could reduce the ambient temperature of our hotbox testing but we chose not to do so as the results would then not be comparable to those of our previous reviews.

High ambient temperatures, even if they are above the unit's rated temperature, do not seem to affect the CM450M significantly. On average, the energy conversion efficiency is reduced by about 0.5%. The efficiency loss is slightly higher as the load increases, reaching a maximum of 0.74% reduction at 100% load. It is nothing short of a miracle for this PSU to be capable of such performance with an ambient temperature higher than 46 °C.

Once again, the low output and high efficiency of the CM450M allow it to maintain fairly low internal temperatures. The maximum internal temperature is just over 71°C at maximum load, with an ambient temperature of 47.2°C. The cooling fan is partially to blame for that, as it now begins to increase its speed faster and reaches a higher maximum speed as well. Nevertheless, the CM450M does operate silently when lightly loaded, even under those adverse conditions. 

Conclusion

When assessing any kind of product, the first task is to determine the targeted audience. In the case of the CS -M series, it is obvious that Corsair is targeting those who are willing to pay a little extra over the cheapest solution possible for a good PSU, yet they still pursue the best bang for their buck. The 450W version that we reviewed today has an output ideal for typical home and office PCs, including medium power gaming systems with a single GPU, which covers a very large portion of the market. The retail price of $80 however is pushing the boundaries of cost effectiveness, as significantly more powerful PSUs can be bought for this kind of money.

Overall, Corsair managed to surprise us positively with both the performance and the quality of the CS450M. We did not expect a record-breaking product for that price, but the CS450M performed better than we anticipated. Due to the low power output and very good efficiency of the PSU, the losses are minimal and the necessity for cooling is relatively low. As such, the CS450M can function almost noiselessly under normal operating conditions. The power quality is good as well, as the CS450M suppresses the maximum voltage ripple on all lines at about 60% of the design limit when operating inside a hotbox and presents good voltage regulation figures. Indubitably, these performance figures are inferior to those we are used to seeing from top-tier units lately, yet the CS450M is not a product designed to compete against those in terms of raw performance.

However, what is even more surprising than the performance of the CS450M is the quality. When checking products of this range, we expect to find components coming from "low cost" (or even unknown) manufacturers. Instead, we found components inside the CS450M typically reserved for higher tier products. For example, all of the electrolytic capacitors that are critical for the long-term reliability of the PSU come from very reputable Japanese manufacturers. Even those of secondary importance are supplied by known manufacturers and are rated for operation at 105°C, a figure that it is next to impossible to be reached inside a 450W unit as efficient as this one. Great Wall did an excellent job making this PSU. It is not by chance that Corsair backs the CS450M with a three-year warranty.

There is only one issue regarding the CS450M. It has only a single 6+2 pin PCI Express connector, meaning that it cannot power many high-performance graphics cards currently available, generally topping out at GeForce GTX 960 or Radeon R9 270. In terms of power output, the CS450M should be able to cope with almost any single GPU card, as long as it is paired with a reasonable CPU and there is no serious overclocking/tweaking taking place. For example, a system with a typical four core CPU and a single GeForce GTX980/Radeon R9 280X GPU could be powered by the CS450M without issues. If someone however tries to power a system with the exotic AMD FX-9590 and a Radeon R9 295X2 with the CS450M, that would certainly not end well. Therefore, to reduce the risk of people making "unwise" hardware combinations despite the hardware specifications, Corsair decided not to provide two PCI Express connectors.

This move however will have everyone who wants to build a standard gaming PC, with just a single good CPU and GPU installed, thinking twice before buying a CS450M. This is especially true if someone is on a tight budget and is looking for used cards, as previous generation high performance models generally use two PCI Express connectors. This despite the fact that the power consumption of such a system with a single GPU should be below 400 Watts, well within the capacity of the CS450M.

With all of that said, there are solutions to the CS450M's limitations. 150-225W cards are increasingly using a single 8-pin connector instead of two 6-pin connectors (e.g. GeForce GTX 960/970). So this is likely a bigger problem in the present than the future, as the CS450M is able to drive those newer 8-pin designs. Meanwhile, adapters can be had to convert a couple of Molex connectors to a PCI Express connector for only a few dollars, with several manufacturers throwing in those adapters with their mid-range cards. Alternatively, one can split off the single 6+2 pin connector, though these are potentially risky as the current can surpass the threshold of a single PCI Express connector if used to drive a card designed for over 225W. In either case it is not impossible to build a very good gaming system powered by the CS450M, yet it pushes the user to either select a proper mid-range card or use an adaptor at the expense of two Molex connectors. 

In summary, the Corsair CS450M is a very well made, reliable PSU that offers good overall performance, though without fancy bells and whistles. It has been designed to compete by offering high quality and good performance at a sensible price. However, the simple lack of two PCI Express connectors reduces the potential market of the CS450M, and requires owners of higher power graphics cards to either look into more specialized video cards, or pay a bit more for an adapter. Otherwise, for the out of the box experience, paying $80 for a PSU to power a sub-300 Watts PC is not a very cost-effective solution and is likely to drive the consumers towards lower cost models.

Meanwhile, the retail price of the CS450M is rather volatile, with the unit being on sale twice in the past couple of weeks alone and the retail price going as low as $57 including shipping. For such a price, the CS450M is a steal for users that want to power a home/office PC or do not mind the use of an adapter to power a performance graphics card. At its current retail price however, $80 is not the kind of fantastic deal that would make us to straightforwardly recommend purchasing the CS450M without some consideration.