Articles: Cases/PSU

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The load capacity of the +12V rail is impressive. Having a total output power of 650W, the PSU can provide 642W across its +12V rail. Traditionally for Corsair’s PSUs, this power rail is not divided into multiple “virtual” 18A output lines. The combined load capacity of the +5V and +3.3V is high at 170W, too. Power Supply Design Guide for Desktop Platform Form Factors requires only 120W from these rails. Well, as we found out once, the real power consumption of a modern PC from these rails is often not higher than half a hundred watts.

The PSU makes all those watts available to you by means of a generous selection of cables and connectors:

  • Mainboard cable with a 20+4-pin connector (60cm long)
  • CPU cable with a 4+4-pin connector (60cm)
  • Two graphics card cables with one 6+2-pin connector on each (60cm)
  • Two cables with four Molex connectors and one floppy-drive plug on each (40+15+15+15+15cm)
  • Two cables with four SATA power connectors on each (40+15+15+15cm)

That’s quite enough for most computer configurations unless you want to assemble a SLI/CrossFire system with two top-end graphics cards each of which has two power connectors. You’ll need power adapters then. The introduction of dual-chips cards from both ATI/AMD and Nvidia has reduced the demand for classic SLI/CrossFire subsystems built out of separate cards, though. Such subsystems are now limited to enthusiasts’ computers which are usually equipped with PSUs of even higher wattage.

This PSU worked without problems at any load from 50 to 650W.

The output voltage ripple is within the norm even at full load although there are accidental short spikes like we have seen with the VX450W model.

Although the PSU features dedicated voltage regulation, it cannot match the superb result of the VX550W because its +5V voltage sags suddenly when there is a high load on the +5V rail. Interestingly, the VX450W, another PSU manufactured by Seasonic, has the same problem.

This problem is not serious from a practical point of view, though. The +12V voltage, the main voltage in a modern PC, is ideal. The +3.3V voltage deflects by slightly more than 3% (while a 5% deflection is considered allowable). And even the +5V voltage remains within 3-4% from the nominal value at load distributions typical of modern PCs.

The PSU has good efficiency: 82% at a load of 100W and a peak efficiency of 87%.

It is partially due to the high efficiency and partially to the large heatsinks, but the results of the fan speed measurement shocked me somewhat: the fan speed is only 500rpm at loads up to 300W!

This is not just a record-breaking result. It is actually unique. The quietest Seasonic S-12 produced more noise even. The Enermax MODU82+ we have reviewed recently may be the only opponent to the Corsair TX650W in terms of noisiness.

Well, the fan accelerates rapidly at loads above 300-350W, making the PSU just good, rather than ideal, in this respect. Its fan is audible at a load of 500W. On the other hand, hardware components that can load the power supply at 500W are not going to be silent, either.

The odd jumps of temperature in the graph above are partially due to the weakness of the air that was flowing out of the PSU because of the low speed of the fan. The horizontal stretch at a load of 200W is obviously a measurement error.

Comparing the TX650W with the earlier-tested TX750W, these PSUs are manufactured by different companies (Seasonic and CWT, respectively) and differ from each other noticeably, even though belong to the same series. For example, the fan of the TX750W was as fast as 1100rpm even at minimum load, making that PSU not really quiet.

The Corsair TX650W is not just quiet. It is actually silent at loads up to 300-350W because you can hardly hear the sound of its fan even in a quietest room. This PSU becomes noisier at high loads but you need a serious PC configuration to achieve such loads. One CPU and one graphics card won’t be enough, for example.

Thus, the TX650W proves to be competitive to the above-discussed VX450W, at least for people who know the value of a silent PC. These two PSUs do not differ much in terms of noisiness but the TX650W costs about two times as much as the lower-wattage model.

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