It is well-known among PC enthusiasts that most hardware companies that sell PSUs do not actually manufacture their products. Instead, they rely on platforms and designs developed and manufactured by the Original Design Manufacturer (ODM). The engineers employed by the various client-brands do perform modifications and/or upgrades to the original design but, more frequently than not, these modifications are limited to aesthetic modifications and the use of a different fan. All of which means that many of these ODM-derived PSU designs are essentially copies of the original platform’s topology and recommended electronic components. In other words, while there are dozens of PSU vendors out there, the PSU industry as a whole is built on the back of a handful of companies.

Over the past decade, several ODMs decided to launch their own retail divisions. The most prominent examples are SeaSonic and FSP Group, whom release new retail products almost every time they upgrade their core designs. FSP Group recently performed a long-overdue update of their retail lineup and presented several fresh products. A few months ago we had a look at their top-end Hydro PTM Pro 1200W ATX PSU, an upgraded version of their tried & true flagship platform that has been around for nearly a decade. In today’s review, we are going to have a look at something significantly different – a very powerful 850W SFX unit, the Dagger Pro.

By traditional metrics, 850 Watts is a lot for a typical small form factor (SFF) PC, but the constantly growing demand for compact--yet-powerful PCs is continuing to drive increasing demand for high-performance SFX PSUs. This is caused primarily by the gaming market, as top-tier graphics cards have substantial power requirements (e.g. 450W for RTX 3090 Ti). On paper, the FSP Dagger Pro 850W is not too impressive by today’s standards, with an 80Plus Gold certification and no extravagant features – but it makes up for that with its tiny dimensions.

FSP Dagger Pro SFX 850W
Power specifications ( Rated @ 50 °C )
RAIL +3.3V +5V +12V +5Vsb -12V
MAX OUTPUT 20A 20A 70.83A 2.5A 0.3A
120W 850W 12.5W 3.6W
AC INPUT 100 - 240 VAC, 50 - 60 Hz

Packaging and Bundle

We received the FSP Dagger Pro inside a relatively large and very sturdy cardboard box that one could easily assume was meant for an ATX unit instead. Inside the box, the small PSU lies inside a very thick packaging foam container. The artwork may be a little excessive but is not really extravagant, with plenty of information printed on all sides of the box.

FSP kept the bundle fairly basic, with just a regular AC power cable, typical mounting screws, and a small manual to be found inside the box. The noteworthy addition to the bundle is the SFX to ATX adapter that allows the Dagger to be installed in ATX-compliant cases, allowing users the flexibility to switch between ATX and SFX cases at will.

With the Dagger Pro being a fully modular PSU, every cable can be detached. This includes the main 24-pin ATX cable. All of the cables are ribbon-like, “flat” type, with black wires and connectors. It is noteworthy to mention that the cables with the SATA and Molex connectors are mixed.

FSP Dagger Pro 850W
Connector type Hardwired Modular
ATX 24 Pin - 1
EPS 4+4 Pin - 2
EPS 8 Pin - -
PCI-E 6+2 Pin - 4
PCI-E 8 Pin - -
SATA - 5
Molex - 2
Floppy - 1

The FSP Dagger Pro 850W SFX PSU

External Appearance

Despite the massive power output of the unit, FSP’s engineers somehow managed to maintain the standard SFX form factor dimensions of 125 × 63.5 × 100 mm / 4.92 × 2.5 × 3.94 in (W×H×D), making the Dagger Pro fully compatible with any SFX-compliant case. The chassis of the Dagger Pro is sprayed with textured black paint.

Stickers with the company and series logos cover both the left and the right side of the chassis. The top side is covered by the sticker with the electrical specifications and certifications of the unit.

One of the major setbacks that SFX PSUs have is that 120 mm fans do not fit into the standard SFX form factor dimensions. As such, FSP had to use a slim 92 mm fan for the Dagger Pro. Regardless, despite the very compact dimensions, FSP somehow managed to place a small on/off switch next to the AC cable receptacle on the rear side of the PSU.


The front side of the Dagger Pro is home to the connectors for the modular cables. A subtle legend is printed on the chassis itself, in the same gold color as the rest of the artwork. The connectors are keyed, so it is not possible to insert any cable into the wrong connector.

Internal Design

The 92 mm low profile fan responsible for the cooling of the Dagger Pro 850W is supplied by Power Logic, a relatively well-known fan manufacturer whose products are frequently found on GPU coolers. It features a simple but very reliable double-ball bearing engine and has a maximum rotational speed of 2500 RPM.

Naturally, there is no third-party ODM behind the creation of the Dagger Pro as FSP designed and built this unit themselves. The interior of the unit is clean but packed to the brim, with the designers clearly having spent many hours trying to make everything fit inside standard SFX proportions. The filtering stage begins at the rear of the AC receptacle and extends over the side of the chassis, with two Y capacitors, two X capacitors, and three filtering inductors total. There are two rectifying bridges that are simply attached to each other, without any heatsink cooling them.


Due to size restrictions, the designers were forced to use three APFC capacitors, the combined total capacitance of which is 420 uF. All three capacitors are supplied by Nippon Chemi-Con. There are two primary side inversion MOSFETs that form the heart of a half-bridge design, feeding a rather small unique transformer.


The secondary side MOSFETs are placed underneath the main PCB and are thermally connected to the chassis of the PSU. This is a common technique in such very compact designs. A vertical PCB on the side of the unit holds the DC-to-DC converters for the 5V and 3.3V voltage lines. Nippon Chemi-Con and Rubycon supply the electrolytic capacitors, while the polymer capacitors are coming from Teapo.

Cold Test Results (~25°C Ambient)
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  • Oxford Guy - Friday, September 16, 2022 - link

    Small form factors and high wattage are generally mutually exclusive, unless you have impaired hearing and no tinnitus.

    'The use of a low-profile 92 mm fan inside such a compact unit with significant thermal losses did have the expected side effect of high audible sound pressure levels.

    Once the fan starts, it quickly becomes clearly audible, with the noise staying within relatively comfortable boundaries up to about 500 Watts.'

    So, maybe these companies should start calling these units 500W models rather than 850.
  • meacupla - Sunday, September 18, 2022 - link

    The only reason to get an 850W for SFX PSUs, is so that the PC won't crash when an RTX 3080Ti, or something as power hungry, causes a massive transient spike.
    You could probably get away with a 750W ATX PSU, but SFX PSUs are known for not handling transient spikes as well as ATX.
  • Harry_Wild - Monday, September 26, 2022 - link

    Looking for a rectangle shape for my Lenovo Workstation SFF desktop! 850W would be great! $170.00 …sold!
  • shamaizas - Saturday, October 15, 2022 - link

  • shamaizas - Saturday, October 15, 2022 - link

    I feel distinctly about it and love adapting also concerning this issue. In the event that conceivable, as you get authority, would you mind restoring your blog with additional data? It is unbelievably huge for me.

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