Final Words

SilverStone’s FX500 sits on a unique pedestal in the retail market, as it is one of the only high performance and high output Flex ATX power supply currently available. Still, if we do not count 1U server applications, the demand for Flex ATX units is low, limited to just enthusiasts and modders who want to build very small (and frequently custom) systems. For those situations, the proportions of the PSU allow for the easy design and fabrication of 3D printed enclosures using widely available consumer FDM 3D printers.


In terms of quality, the SilverStone FX500 is a well-designed and made power supply. Channel-Well Technologies is a reputable OEM whose designs we frequently encounter in advanced PC PSUs, and SilverStone ensured that the FX500 is assembled with fine quality components, the combination of which should result in a highly reliable product. Considering that these platforms were originally intended to power 1U servers 24/7, the longevity of the FX500 is pretty much assured.

The performance of the SilverStone FX500 left us with mixed feelings, however. On the upside, the electrical performance of the PSU is very good, especially after taking into account the massive space restrictions that the designers had to deal with. It delivers good power quality and the efficiency is just as high as advertised. However the thermal performance is practically incomparable to that of more typical ATX PSUs and, as one would expect for such a compact PSU, thermal stress became an issue while the unit was operating inside our hotbox. This is an edge case for most users, as few people enjoy hanging out in rooms that are over 40 degrees Celsius, but it goes to show how the PSU's cooling is right on the knife's edge. Nevertheless, the FX500 was able to perform normally even when its internal temperature was very high, only finally stopping once forced to shut down by its protective circuitry.

Unfortunately the counterpart to thermals – noise – proved to be a bigger concern, and we believe that this is the the Achilles' heel of the SilverStone FX500. Put simply, the PSU is noisy, which generally rules out using it in any kind of household computer. Most people will find the noise generated by the 40 mm fan intolerable even while the system is idling, and under high loads it is noticeable even through headphones.

Ultimately, this kind of noise would not a problem for server applications, but it is one of the prime deciding factors for home users. Which is why we believe that it greatly limits the market potential of the FX500; there just aren't very many scenarios where a loud PSU is okay in the consumer space. In the meantime, we are hopeful that SilverStone can learn from the FX500 and future Flex ATX implementations will be able to better balance their power output with their thermal performance, and ultimately offer home PC builders quieter power supplies.

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  • RealBeast - Thursday, November 12, 2020 - link

    Doh, this looked promising for a small custom HTPC build until I read the sound issue.
  • Lucky Stripes 99 - Thursday, November 12, 2020 - link

    If you are looking for a nearly silent PSU for a SFF HTPC, good luck finding one. Almost all of the FlexATX PSUs use little 40mm fans that struggle to move air quietly. Even the 160W unit in my Inwin Chopin case was noticeable when using it as a HTPC. So I pulled the original PSU and replaced it with a fanless 12V DC-DC ATX pico-PSU style board paired with a 220W 12V laptop brick. Since the majority of the work is being done outside of the case, the Noctua HSF atop my AMD 3400g is enough to keep the DC-DC board cool. The downside of a pico-PSU style board is that it is a tight fit near my memory modules, but since nobody makes a FlexATX sized DC-DC supply outside of some stupidly expensive ($200+) industrial models, it was the route I was stuck with.
  • rabw - Friday, November 13, 2020 - link

    If you have room for a SFX PSU, the Corsair SF750 is passive up to 300W.
  • Valantar - Friday, November 13, 2020 - link

    There are options, but you need to abandon traditional form factors. I just built a silent, semi-fanless Renoir HTPC using a MeanWell RPS-200-12C AC-12VDC PSU plus a plug-in DC-ATX board. The PSU can run on convection cooling up to ~150w, which far outstrips the needs of my 4650G.

    Still, the market for this Silverstone unit is more for the people buying SFF cases off TaoBao - there are dozens if not hundreds of designs there for FlexATX PSUs and relatively large GPUs, and until now the only real PSU option has been refurbished server units. I'm expecting a lot of these will get Noctua fan swaps in short order though.
  • DanNeely - Thursday, November 12, 2020 - link

    There's no way to move a meaningful amount of air with a 40mm fan that's not going to be loud.

    Sadly, it doesn't appear to have a low power fanless level. At least 50-100W should be doable (maybe a bit more); that's a mainstream laptop power brick, and if being inside a case means this won't have as easy passive cooling it's also several times larger than a brick.
  • MenhirMike - Friday, November 13, 2020 - link

    If you only need 50-100W, then a PicoPSU is a great option. Looks like they have models that go up to 160W, I myself have an 80W Model (only with a 60W laptop power brick though) and it does what it needs to do.
  • DanNeely - Friday, November 13, 2020 - link

    If you never need more than that much power, then yes something like this would always be the wrong choice. ~100W before the fan came on would be for an SFF system with a discrete GPU that was near silent at idle and only made noise under load.
  • Lucky Stripes 99 - Friday, November 13, 2020 - link

    There are now numerous PicoPSU clones on the market with much higher peak wattage. HDPlex has 200W models, RGeek has 250W models, and G-Unique has 450W models.
  • meacupla - Friday, November 13, 2020 - link

    You can add an 80mm fan to the side if you cut a hole into the side of it.
    Of course, it's no longer Flex ATX sized at that point, but it's still smaller than an SFX PSU.

    There are also TFX PSUs, but they tend to lag even further behind than Flex when it comes to higher power output.
  • Spunjji - Friday, November 13, 2020 - link

    If you're after something quiet and don't need high power output then FSP make a 150W fanless model, the FSP150-50FGBBB. It doesn't have a lot of connectors, though, so you'd need to plan a build accordingly.

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