Original Link: https://www.anandtech.com/show/16844/the-silverstone-sx1000-sfxl-1-kw-psu-review



For better or worse, the amount of power required by top tier PC gaming systems has been on the rise over the last few years. Lead in large part by a leap in video card power consumption – gone are the days where a flagship video card would draw just 250 Watts – the required and recommended wattages for high-end systems have started encroaching on the kind of power that dual GPU systems required barely half a decade ago. So although dual GPU configurations themselves have all but died, their high power requirements have been replaced with even more energy-hungry video cards and CPUs.

All the while this has been going on, it's created something of an usual side benefit of dual GPU gaming systems going the way of the dodo: you can get true flagship-level performance in an impressively small system. Small form factor PCs are of course hardly new, but previously there was always some trade-off in the total amount of stuff you could, well, stuff in such a system. A second video card, another 2.5-inch SSD, etc. The death of dual GPU systems has done away with that issue, but now it's created another issue: powering a modern dense, high wattage system.

For a typical ATX system this isn't a problem, as there are myriads of products available and users can easily find very powerful and reliable PSUs at reasonable prices. However, this quickly becomes an issue with small form factor systems, where the availability of high output PSUs is relatively low. And this brings us into the realm of more specialty form factors.

Over the past couple of years, several of the larger PSU manufacturers released compact SFX and SFX-L PSUs that were designed to match the power requirements of powerful gaming systems. With power output ratings reaching 700 Watts or more, some of them could even power flagship-level PC gaming systems. This was quite the feat considering that finding a quality SFX PSU even for a mainstream gaming system was a very difficult task until a few years ago.

But, for some customers, even 700 Watts isn't going to be enough. Especially as you start blending over into the high-end workstation space – think multiple Radeon Pro workstation cards here – even more power is required. So to fill that role SilverStone has rolled out a 1000 Watt SFX-L form factor PSU, the SX1000.

Already well-known for products like their SFX design-pushing SX800-LTI 800W PSU, the company has gone back to the drawing board in an effort do one better. We did not expect that the company would easily manage to squeeze even more power out of an SFX PSU, and yet nearly three years after the release of the SX800, here we are: SilverStone has an SFX-L PSU with the frightening output of 1 kW. This currently is the most powerful SFX-L PSU on the market, so of course we need to take a look at it to see how it stacks up.

Power specifications ( Rated @ 40 °C )
AC INPUT 100 - 240 VAC, 50 - 60 Hz
RAIL +3.3V +5V +12V +5Vsb -12V
MAX OUTPUT 25A 25A 83.3A 3A 0.3A
125W 999.6W 15W 3.6W
TOTAL 1000W
 

Packaging and Bundle

SilverStone supplies the SX1000 into a fairly large cardboard box that could easily fit a regular ATX unit in it. The box is very sturdy and we found the PSU sandwiched between thick polystyrene foam pieces inside, providing ample shipping protection. The artwork is relatively simple, with a blue and gold visual theme, and mostly limited to pictures of the unit itself.

Inside the box, we found a fair bundle for a good PSU. Aside from the manual and datasheet, there is a typical AC power cable, a few cable ties, a few plain cable straps, four black thumbscrews, and four black M3.5 mounting screws. Strangely, SilverStone does not supply an SFX-to-ATX adapter with the SX1000. The company used to do so in the past with models that had almost half the power output of the SX1000, making it a noticeable and strange departure, especially as these powerful units are far more likely to find their way into ATX-compliant cases than low-output models.

The SX1000 is a fully modular PSU, meaning that every cable can be detached, including the 24-pin ATX cable. Making the 24-pin ATX cable detachable usually does not make any practical sense, but it does in this case: allowing the user can replace the short 12” ATX cable with a longer version if the PSU is going to be installed inside an ATX case. Without any exception, all of the cables are “flat” type cables, with black wires and black connectors.

SilverStone SX1000
Connector type Hardwired Modular
ATX 24 Pin - 1
EPS 4+4 Pin - 2
EPS 8 Pin - -
PCI-E 6+2 Pin - 6
PCI-E 8 Pin - -
SATA - 8
Molex - 3
Floppy - 1

The SilverStone SX1000 1 kW PSU

External Appearance

The SilverStone SX1000 is an SFX-L unit, meaning that it is based on the SFX standard but it is 30 mm deeper. Its chassis measures 125 (W) × 63.5 (H) × 130 (D) mm (4.92 x 2.5 x 5.12 inches), which does limit the compatibility of the PSU, as several SFX-compliant cases do not provide that kind of clearance. Nevertheless, cases meant to hold SFX PSUs and multiple/oversized video cards should all be providing enough clearance for an SFX-L PSU.

SilverStone is not a company that designs visually extravagant products and the SX1000 sticks to that tradition, with the designer sticking to a classic all-black design. The chassis is sprayed with satin black paint but most of its surface is covered by stickers. The stickers on the sides of the unit only display the company and product logos, whereas the sticker that covers the entirety of the unit’s top side hosts the basic electrical specifications and certifications of the unit. At the bottom side of the unit, we can see the black fan and the finger guard, with a metallic crest featuring the company’s logo covering the fan’s engine.

Despite the very cramped space requirements, the designer still managed to fit an on/off switch next to the AC receptacle. The front side of the unit is covered by numerous cable connectors, along with a sticker that hosts a basic legend. All of the cable connectors except those of the ATX cable are covered with plastic protective caps.

 

Internal Design

A major advantage of the SFX-L form factor is that it allows for 120 mm fans to be installed, a necessity for the cooling requirements of such a powerful unit. Globe supplies the low profile 120 mm fan, which is a double ball bearing model with a maximum speed of 2400 RPM at 12 Volts. This is a strange choice by SilverStone, as the company usually prefers to use sleeve bearing fans because of their lower noise output, even for their top-tier products.

Although the SX1000 externally reminds us of the older SX800-LTI, they are nothing alike internally. The OEM behind the creation of the PSU remains the same with Enhance Electronics, the company behind most of SilverStone’s PSUs. That is where the similarities end though, as the SX1000 is based on a newer, different platform.

 

The filtering stage of the SX1000 is slightly beefed up, as it begins at the rear of the AC receptacle and continues onto the main PCB, with four Y capacitors, four X capacitors, and two filtering inductors. There are two APFC capacitors, supplied by Rubycon, rated at 400 V / 470 μF each. A large filtering inductor sits right next to them. The heatsinks are rather basic for a PSU with that kind of output, with relatively little mass and surface area. We would not expect to see such heatsinks in ATX units rated above 600 Watts, yet the limited space in the SX1000 requires certain sacrifices. That does not mean that the temperatures of the components should skyrocket but does hint the use of special very low loss parts that will generate minimal amounts of heat – which also are relatively costly.

The primary inversion circuit is a proven with an LLC resonant full-bridge topology. Eight MOSFETs generate the 12 V rail on the secondary side of the unit. The minor rails are being generated via DC-to-DC converters. The strange part here is that the topologies of the SX1000 are a step up compared to the half-bridge topology of the SX800-LTI, yet the unit still failed to receive an 80Plus Titanium efficiency certification. The capacitors on the secondary side are a mix of electrolytic and solid-state products, with most of them supplied by UniCon. There are a couple of small Rubycon electrolytic capacitors in there as well.



Cold Test Results (~25°C Ambient)

For the testing of PSUs, we are using high precision electronic loads with a maximum power draw of 2700 Watts, a Rigol DS5042M  40 MHz oscilloscope, an Extech 380803 power analyzer, two high precision UNI-T UT-325 digital thermometers, an Extech HD600 SPL meter, a self-designed hotbox and various other bits and parts. For a thorough explanation of our testing methodology and more details on our equipment, please refer to our How We Test PSUs - 2014 Pipeline post.

True to its specifications, the SilverStone SX1000 easily reached 80Plus Platinum efficiency levels while operating with a 115 VAC input. The increase in efficiency that switching to a 230 VAC input offers is measurable, but it would not be enough to grant the SΧ1000 an 80Plus Platinum certification, as the efficiency at 50% load did not surpass 94% as required by the protocol. Nevertheless, the efficiency figures are very good by any standard.

With that said, there is still significant room for improvement on the lower end of the curve, as the efficiency drops very sharply when the load is lower than 7-8% of the unit’s rated capacity. This is a small fraction of the PSU's total output, but still a significant amount of power on an absolute basis thnaks to the unit's high output.

SilverStone designed the SX1000 to be semi-fanless, i.e., the fan only spins when the load or temperatures are high enough to necessitate it. 80Plus Platinum units are efficient enough to operate in fanless mode until the load reaches several hundred Watts. The SX1000 was true to that rule, starting its fan when the load reached 300 Watts and remained this high for a few minutes. That is high enough to ensure that the fan will never spin when the system is idling or performing simple tasks.

Because the thermal circuit only starts the fan when the load is 300 Watts or greater, there's a fairly narrow window where the fan remains relatively quiet. If the load exceeds 500 Watts, the tiny heatsinks of the SX1000 cannot cope with the thermal losses and the demand for cooling falls upon the low-profile fan, which will keep increasing its speed in order to maintain the internal temperatures of the PSU within safe levels. The fan reached its maximum speed with a 90% load, while the SX1000 was operating unobstructed and in a room temperature environment.



Hot Test Results (~45°C Ambient)

For the testing of PSUs, we are using high precision electronic loads with a maximum power draw of 2700 Watts, a Rigol DS5042M  40 MHz oscilloscope, an Extech 380803 power analyzer, two high precision UNI-T UT-325 digital thermometers, an Extech HD600 SPL meter, a self-designed hotbox and various other bits and parts. For a thorough explanation of our testing methodology and more details on our equipment, please refer to our How We Test PSUs - 2014 Pipeline post.

The SX1000 is designed to deliver its advertised performance with an ambient temperature of up to 40°C, a bit cooler than our standard 45°C hotbox. Although the unit did operate inside the hotbox without significant issues and did not shut down even at maximum load, there were significant signs of thermal stress. Naturally, the energy conversion efficiency takes a hit, dropping an average of almost 1% across the load range. The drop, however, is not equally distributed, as the SX1000 is almost just as efficient as it was outside the hotbox until the load reaches 40%, then the efficiency degrades as the load increases, and the efficiency drop is almost 1.7% at maximum load. This suggests that the components are getting significantly thermally stressed – which is to be expected, looking at the internal temperatures of the unit.

Rarely ever we see temperatures greater than 100 °C inside a PSU, either because their cooling is sufficient or because their thermal protection circuitry will shut them down. Neither was true for the SX1000, as the temperature did surpass 100 °C under maximum load with the unit operating inside our hotbox. Still, the SX1000 stayed in operation and performed within the expected parameters, even though it was clearly on the verge of shutting down due to thermal overload.

Even though we would expect the fan of the SX1000 to start almost immediately inside our hotbox, it actually did not. The thermal circuitry started the fan when the load reached 100 Watts, meaning that the SΧ1000 should stay dead silent with the PC idling even inside a very hot enclosure. Still, once the load increases even slightly above that point, the fan will start and its speed will start increasing sharply, as the SX1000 is trying to cope with the thermal load in these adverse conditions. It reaches its maximum speed when the load is just 400 Watts, with the sound pressure levels being very high at this point. With the fan unable to do anything more for the cooling needs of the SX1000, the internal temperatures reach uncomfortably high levels when the PSU is heavily loaded under such operating conditions.



Power Supply Quality

As part of our testing, we also check output parameters are within specifications, as well as voltage ripple and line noise.

Main Output
Load (Watts) 202.65 W 505.85 W 753.59 W 1001.78 W
Load (Percent) 20.27% 50.58% 75.36% 100.18%
  Amperes Volts Amperes Volts Amperes Volts Amperes Volts
3.3 V 2.27 3.39 5.66 3.39 8.5 3.33 11.33 3.31
5 V 2.27 5.13 5.66 5.08 8.5 5.06 11.33 5.01
12 V 15.1 12.14 37.75 12.13 56.62 12.05 75.5 12.02

 

Line Regulation
(20% to 100% load)
Voltage Ripple (mV)
20% Load 50% Load 75% Load 100% Load CL1
12V
CL2
3.3V + 5V
3.3V 2.1% 12 20 22 26 18 22
5V 2.25% 18 26 30 34 20 26
12V 0.92% 16 32 46 78 76 30

The electrical performance of the SilverStone SX1000 is good and within our expectations for an Enhance platform. Line filtering could use some improvement, as the voltage ripple figures are relatively high, with our instruments recording a maximum of 78 mV, 34 mV, and 26 mV on the 12V, 5V, and 3.3V lines respectively. These figures are adequate, but top tier units easily halve these values. Meanwhile line regulation is significantly better, with the 12V line maintaining a regulation factor of 0.9%. The regulation of the 3.3V and 5V lines is a little higher than 2%, which is enough for a modern design.

Conclusion

Unlike ATX PSUs, SFX designs have still seen significant development over the past few years. Not only has their power output increased considerably, but their overall performance dramatically improved as well. SilverStone is a company strongly focused on the R&D of small form factor cases (SFF), systems, and other related parts. They have several compact cases and products designed for high-end living room systems, including designs that were designed with gamers in mind. Therefore, their efforts to market the very best SFX PSUs available are not unfounded. The SilverStone SX1000 is a noteworthy milestone as it has a tremendously high-power density, delivering power that it would be difficult for a physically larger standard ATX unit to deliver about a decade ago.

While the SX1000 is, for the moment at least, the most powerful SFX/SFX-L unit on the planet, its overall performance left us with mixed feelings. In some ways it feels as if it is a small step back from the SX800-LTI, a unit that delivered better energy conversion efficiency and power output quality. The electrical performance of the SX1000 is not bad at all – it does meet all 80Plus Platinum certification and quality standards with ease – it is just a little worse than its less powerful predecessors. It also struggles to maintain reasonable noise and temperature levels when the load is very high, even when the operating environment is relatively cool. However, due to the possibility of high internal temperatures, the designer is using very high-quality components so that they will not be thermally stressed. This bodes well for the quality and longevity of the SX1000, as these components will perform very reliably under normal operating conditions.

Much like most top-tier SFX units, the SX1000 is struggling to find its identity in the retail market. Its SFX-L design limits its compatibility with SFX cases and there is no adapter to install it inside an ATX-compliant case either – in which case, the length of the cables could be a problem. It is powerful enough and has enough connectors to power a top-tier motherboard and two graphics cards, yet such motherboards and two cards will not fit in the vast majority of SFX-L compliant cases. Only an SFX case designed to hold a top-tier Micro ATX motherboard and four slots' worth of graphics cards would be a reasonable match for the SX1000.

The creation of a powerful gaming small form factor PC for the living room is the heartfelt desire of every serious gamer. Still, few are determined (and deep-pocketed) enough to be able to justify an aesthetically elegant and compact gaming PC with a flagship graphics card in it. Nevertheless, SilverStone’s latest PSU is designed to specifically target that small, yet existent, segment of the market. More pragmatically, perhaps, it could also be used to power systems with a single high-end graphics card while operating near its half capacity, offering top efficiency and reliability. However, the very high retail price of $366 at this writing severely limits the market potential of the SX1000, as only users who do not care about having a budget when building a PC would purchase it. 

 

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