900W to 1100W PSU Group Test

Seasonic X-900 Results

Only at 100 percent load does one of the 12V fall to the one percent region but they all still remain within the ATX specification. The 3.3V and 5V at full load seem really very low, but that's because the unit is only capable of outputting 72 Amps (864W) through the 12V rails which leaves 36W for the rest of the system?

The 3.3V and 5V rails top out at 24 and 30 Amps respectively, of which we get close to at 75 percent load and you can see the 5V drops 0.06V from 50 percent so we can only estimate that it'll drop another 0.6 percent meaning it'll within one percent of the ATX specification.

Rarely are PSUs setup so that you can run every rail at its maximum, and you reach the peak output through a combination of them far earlier, but just two amps out of 24 or 30 is an extreme case. Our results are far better than the previous ones of the Seasonic M12 700W Modular, which failed on the 5V rail at both 50 and 75 percent.

The efficiency is really very good throughout but drops off from a superb 84 percent to just over 80 percent as we go from 50 to 100 percent load. The PFC rating on the other hand is phenomenal, getting better as the PSU is loaded to having a massive 99.5 percent. A higher power factor represents a more effective use of electrical power and at around 1kW even a small amount of extra PFC should rack up the saved pennies.

Warranty

Nothing on the box or in the manual tell you how long your warranty is three years, with the first year being returned to the point of sale and subsequent years are returned to Nanopoint in the UK.

Value

At the intended £152.73 (inc. VAT), the Seasonic is about the right price, slightly above the many 850W models but still quite a bit lower than the 1000Ws. It'll still be slightly cheaper than the 850W Enermax Galaxy DXX, and likely much quieter, but the Galaxy comes with 8-pin PCI-Express connectors and partial modularity. You could argue an extra 50W isn't much, but then again is another 100W above that?

If we review the PSU on being a truly silent and excellent 500-750W then its value is going to massively plummet since that's the performance-mainstream market which provides the best value at the moment. I know there are a few of you who'll only buy a certain brand and in that respect the Seasonic M12 700W Modular we previously reviewed is £135 (inc. VAT) and unless you absolutely require a modular PSU go for the X-900 any day.

Conclusion

At typical usage values of 50-to-75 percent you'll get a very quiet to silent PSU, but if you're really hammering it the fan will really crank up to compensate for the elevated heat output. You'll be unlikely to hear it at its loudest and even though it's a 900W model, the design of the cabling and power output, as well as inherent ethos for silence at Seasonic implies that this isn't a 900W PSU. Instead it's more of a truly silent performance-mainstream product that is capable of sustained 900W load.

This is a difficult situation because you can't compare its value to mainstream products which are clearly cheaper, but it's not really designed to compete at the very high end either. If you are looking for a 500-750W PSU that is truly silent along with having a massive PFC rating and great efficiency, the Seasonic 900W is without a doubt the one to invest in. But for a true 900W PSU it is capable of it delivering the power, but at very elevated noise levels and it doesn't supply the inherent capability as the provided cables are very limiting.

Seasonic makes Corsair's PSUs and the HX620 is actually a 750W model that's underrated because Corsair want to guarantee silence. This is exactly what Seasonic should do with the X-900, but unfortunately because the company brands it as a 900W unit, it doesn't score as high as it should.

• Performance
• x
• x
• x
• x
• x
• x
• x
• x
• -
• -
• 8/10

• Features
• x
• x
• x
• x
• x
• x
• x
• x
• -
• -
• 8/10

• Value
• x
• x
• x
• x
• x
• x
• x
• x
• -
• -
• 8/10

• Overall
• x
• x
• x
• x
• x
• x
• x
• x
• -
• -
• 8/10

What do these scores mean?