Quite expectedly, the specs coincide with those of the 1000W model except for the load capacity of the +12V rail. Following today’s trends, the load capacity of the +3.3V and +5V rails is low but the PSU can yield almost all of its output power via the +12V rail.
This PSU complies with the 80 PLUS Platinum standard which is the highest certification among the PSUs in this review.
Working with our APC SmartUPS SC 620, this PSU was stable at loads up to 430 watts when powered by the mains and could switch to the UPS’s batteries at 340 watts.
Cross-Load Voltage Stability
The main +12V voltage is perfect. It is never even 1% off the required level at any load.
The +5V voltage is immaculate as well. It is only at low loads that it is more than 1% off.
The +3.3V voltage is not that stable. It deflects by more than 2% at minimum loads (although Seasonic promises its Platinum-certified PSUs to keep voltages within 2% on every power rail).
Anyway, the PSU is exemplary in terms of output voltage stability.
Output Voltage Ripple
Although the voltage ripple isn’t strong, we’ve seen Seasonic PSUs perform better in this test. The high-frequency ripple is weak on the +3.3V and +5V rails but conspicuous on the +12V rail. On the other hand, it’s only half the permissible maximum even on the +12V rail.
At the double frequency of the mains the voltage ripple on the +12V rail isn’t that strong, though.
Temperature and Noise
As other top-end Seasonic PSUs, the SS-860XP is cooled by a 120mm fan Sanyo Denki San Ace 120 (model name: 9S1212F404, rated speed: 2200 RPM). You can refer to our earlier reviews for details about this fan’s advantages and special features.
We tested the SS-860XP in both operating modes of its fan.
In the Normal mode the fan has a start speed of about 800 RPM and maintains it until a load of 700 watts. Then the fan accelerates suddenly but doesn’t reach even 1200 RPM at full load, making the PSU virtually silent all the time.
In the Hybrid mode the fan is idle at low loads or turns on but for a little while. This mode doesn’t differ from the Normal one at loads above 300 watts when the fan rotates constantly.
The Seasonic SS-860XP is one of the quietest models in its class. For example, the above-discussed Cooler Master turns out to be noisier at the same speed of the fan because its fan is larger and not as high quality as the Sanyo Denki.
Efficiency and Power Factor
The Seasonic SS-860XP is 90.4%, 92.9%, and 90.5% efficient at the reference loads of 20%, 50% and 100%, which agrees with the 80 PLUS Platinum requirements. The peak efficiency was 94.2% at 395 watts.
The power factor is 98 to 99% at most loads, which is normal for a PSU with active power factor correction.
The standby source copes with its job without any problems.
The Seasonic SS-860XP is a masterpiece with its superb electrical parameters, very quiet operation, handy modular design and stylish appearance. It is priced accordingly, though.