As one of the best-known companies in the high-end PC peripherals business, SilverStone needs little introduction. The company has made a name for itself with its variety of boutique products, especially off-beat and compact designs. And, even though the company has diversified over time into several other segments of the market, their unique cases and assorted power supply units (PSUs) remains their most defining product lines to this day.

It's a field that SilverStone has become so entrenched in that although other companies produce compact PCs and related peripherals as well, none of them are really trying to be SilverStone's peer. As a result, SilverStone is one of the very few companies with a true variety of small form factor power and cooling solutions, rather than just a token device or two. Even with relatively standard, ATX-compliant equipment, SilverStone’s power products tend to have great power-per-volume ratios.

For today’s review, we are taking a look at the FX500, a very different PSU than the typical ATX fare that we typically cover. SilverStone’s FX500 is a Flex-ATX format PSU, with the tiny physical proportions that entails, and yet can output up to 500 Watts while meeting 80Plus Gold efficiency standard. Few OEMs – let alone retail companies – bother to develop advanced PSU platforms that are smaller than the full ATX format, making compact PSUs an underserved market. All told, we have seen a few high-end SFX units in the past couple of years, but nothing smaller or even different than that. This makes the the Flex-ATX FX500 a very rare product, as one of the only high-power Flex-ATX PSUs on the market.

Power specifications ( Rated @ 40 °C )
AC INPUT 100 - 240 VAC, 50 - 60 Hz
RAIL +3.3V +5V +12V +5Vsb -12V
MAX OUTPUT 14A 17A 41.67A 2.5A 0.3A
90W 500W 12.5W 3.6W

Packaging and Bundle

SilverStone supplies the FX500 PSU in a simple cardboard box that is half the size of boxes designed for ATX products. The artwork on the box is simplistic, with a plain blue/white color theme and a picture of the PSU itself on the front side of the box. Inside the box, the PSU is merely wrapped in a bubble bag, with SilverStone betting that its small proportions and low weight are enough to prevent damage during transport.

Inside the box, we found only the basics that come with any retail PC PSU. Altogether, the PSU comes with four mounting screws, an AC power cable, and basic instructional leaflets. There are no cable straps, cable ties, or other accessories of any kind.

SilverStone FX500
Connector type Hardwired Modular
ATX 24 Pin 1 -
EPS 4+4 Pin 1 -
EPS 8 Pin - -
PCI-E 6+2 Pin 2 -
PCI-E 8 Pin - -
SATA 4 -
Molex 3 -
Floppy 1 -

The SilverStone FX500 Flex-ATX 500W PSU

External Appearance

A mere glance on the FX500 once unpacked is enough to leave most experts wondering how a designer managed to fit a platform with 80Plus Gold efficiency at 500 Watts inside such a small chassis. The body of the FX500 is merely 81.5mm/3.21" (W) × 40.5mm/1.59" (H) × 150mm/5.91" (D), occupying barely a quarter of the volume of a typical ATX PSU. Even its own cables take up more space than the body of the PSU itself.


The sticker with the unit’s electrical certifications and specifications covers most of the top surface, with intake airflow vents on the rest. Despite the very limited design options, SilverStone’s engineers did try their best to make this PSU aesthetically appealing. As a result, the FX500 has an all-black chassis, cables, and connectors. The cables are of “flat” type, without external sleeving, in an effort to minimize their volume as well.

SilverStone’s engineers managed to fit a switch next to the AC receptacle at the rear side of PSU. Concerning the tiny proportions of the unit, even the presence of a switch must have been a design challenge. The tiny 40 mm cooling fan of the PSU covers the rest of the rear side’s surface and is supplied by YS Tech, whose products we frequently encounter into middling-to-premium range PSU products.

Internal Design

The OEM behind the platform of the FX500 is Channel-Well Tech (CWT), a company that developed and marketed several Flex-ATX platforms for 1U systems in the past. Yet none of those were as powerful as this variant. The textbook filtering stage is crammed and shielded right behind the AC receptacle, which comes as no surprise due to the lack of space.


There is only one significantly-sized heatsink inside the PSU, which is used to cool the two transistors that form a typical half-bridge primary inversion stage. The primary APFC capacitor is a 400V/220μF electrolytic capacitor made by Nippon Chemi-Con and is supported by a very sizable coil that takes almost as much volume as the main transformer of the PSU does.

The secondary side conversion stage is also simplistic, with just a couple of MOSFETs generating a single 12V line. The rest of the voltage lines are being generated by DC to DC converters that are mounted on secondary boards. Nearly all of the secondary capacitors are solid-state polymer products and are supplied by APAQ, a Taiwanese manufacturer. The cables are soldered directly near the edges of the main PCB. The PSU’s designer clearly had no hope of making this platform into a modular design without increasing the unit’s length – there is simply not enough space for the connectors.

Cold Test Results
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  • Lucky Stripes 99 - Friday, November 13, 2020 - link

    I'm curious how the other cooling components in a SFF case would react to having a passive AC-DC PSU like that running at high loads. You might just be pushing the noise and heat issues to other parts of the case. It may be an acceptable trade-off if they can do the job more quietly, but it may not turn out as quiet as you might hope. For the price, there are better alternatives.
  • plewis00 - Thursday, November 12, 2020 - link

    Is this actually that impressive for size? How does it compare to an HP 1200W server PSU? Yes I know those are loud (at full load but manageable at low load) and 12V-only but they’re capable of 1200W sustained at 240V and Platinum-rated. So is this Silverstone that much of a feat?
  • thecoolnessrune - Thursday, November 12, 2020 - link

    Yes, I would definitely say it's still impressive. The Flex-ATX PSU is around 150mm long. Those 1U Server PSUs are over twice that, usually in the 330mm range. That leaves a lot more room more more circuity to get efficiency up in the Titanium range, and leaves a huge amount of room for heatsinking in the path of the air channel. In addition to that, the server PSU has an edge finger connector vs having to solder wires onto the PCB, further decreasing the real estate needed for functions that don't involve cooling the unit. A last point is that most of these modern server PSUs do not have the further conversion circuity for 5V and 3.3V busses. They outboard that to the Power Management Module. I'd say it's pretty impressive that they were able to cram wiring, low voltage conversion circuitry, and a ~450W power output in a 150mm chassis length. But it definitely came at a cost. An extra 50mm of length would have made a world of difference.
  • plewis00 - Thursday, November 12, 2020 - link

    Where on earth did you get the dimensions from? I just pulled one of the HP Common Slot PSUs from a Proliant in the office and it’s not that large - HP says they’re 3.81 x 8.63 x 19.05 cm which is not a lot bigger - and they can go up to 1200W. Yes they’re a bit larger and they don’t have wires but the edge connector takes up similar space to directly connected wires. They’re missing 5 and 3.3V rails but how much space do they take? A slightly larger PSU that is highly efficient and has a much higher wattage seems to be similar ballpark to me.
  • versesuvius - Thursday, November 12, 2020 - link

    Could you please read what you write at least once before publishing it? This kind of writing is becoming a trend in Anandtech (sign of the times?):

    "As a result, SilverStone one of the very few companies with true a variety of small form factor power and cooling solutions, rather than just a token device or two."
  • ElectroChem - Thursday, November 12, 2020 - link

    The previous sentence is no better.

    "It's a field that SilverStone has become so entrenched in that although other companies that produce compact PCs and related peripherals as well[sic[ , none of them as [sic[ really trying to be SilverStone's peer."

    Would it kill them to hire a proof-reader?
  • justaviking - Thursday, November 12, 2020 - link

    As long as we are on this topic... maybe it's just me, but...
    Page 1, third paragraph...
    You wrote: "making company PSUs an underserved market"
    Did you mean to say... *compact* PSUs...?
  • Ryan Smith - Friday, November 13, 2020 - link

    Thanks guys!
  • Ej24 - Thursday, November 12, 2020 - link

    Wonder if you could easily swap that fan for a 40mm x 20mm noctua? That'd probably move just as much air and be quieter. Don't have a need for such a tiny psu. But I'm sure I could dream of a need lol
  • Lucky Stripes 99 - Thursday, November 12, 2020 - link

    Just be mindful of the static pressure and air movement rating of the original fan and any replacement you purchase. You can probably shave a few db off with a Noctua versus stock, but I wouldn't expect miracles.

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