SilverStone loves to make its PSU offerings smaller and smaller, while retaining the power output at the same levels. The ST1200-PTS is the smallest, in dimensions, 1200W unit available on the market today with 140mm depth, with the majority of similar capacity offerings being at 180mm. This is 40mm less meaning that components like the main transformer and the heat sinks that cool down the primary and secondary FETs along with the cooling fan of course, had to be as small as the parts used in 600-750W units. The only way to use smaller heat sinks and a 120mm fan was to increase the platform's efficiency, in order to minimize energy losses, and indeed this is the case with the ST1200-PTS.
The SilverStone ST1200-PTS is not perfect, with its major problems being the low hold-up time and the inaccurate power ok time, with the latter being a real shame for such an expensive PSU. By sending an inaccurate power ok signal to the system's components the PSU actually fools them into believing that its voltages are safe to use, something that is not the case once the +12V rail drops below 11.4V and the 5V and 3.3V below 4.75V and 3.14V respectively. I don't know why Enhance Electronics, the manufacturer of this unit, didn't bother to check the accuracy of the power ok signal but for me it is of immense importance this signal to be accurate, because low voltages significantly increase the stress on the power conversion circuits of parts like the mainboard, the graphics card(s), the drives etc.
Another problem with the ST1200-PTS is its inability to provide full load with 100V input. SilverStone states that the lower voltage input for this unit is 100V, so I expected no problems in this scenario.
It is expected that several compromises in performance had to be made to achieve such small dimensions. Nevertheless, the SilverStone ST1200-PTS achieves a much higher overall performance compared to its predecessor, the ST1200-PT and, above all, it manages to keep the noise low under light and mid loads. Currently there is no other 1200W unit featuring such a high power density score, so the ST1200-PTS is the only choice for anyone wanting a 1200W power supply with only 140mm depth. I would like to see SilverStone address some of the issues I found, though, in the next version of this model.
Photo Credits: Tom's Hardware
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Disclaimer: Aris Mpitziopoulos is Tom's Hardware's PSU reviewer. He is also the Chief Testing Engineer of Cybenetics, and developed the Cybenetics certification methodologies apart from his role on Tom's Hardware. Neither Tom's Hardware nor its parent company, Future PLC, are financially involved with Cybenetics. Aris does not perform the actual certifications for Cybenetics.