Tom's Hardware Verdict

This is the best passive PSU that money can get you today. It is super efficient, its overall performance puts to shame many high-end active cooling PSUs and it can easily support a strong gaming system. The only downside is the stiff price, but you get what you pay for, with this product.

Pros

+
Resilient to high temperatures
+
Efficient
+
Ripple suppression
+
Load regulation
+
Hold-up time
+
Accurate Power Ok signal
+
5VSB performance
+
Dead silent
+
Fully modular
+
2x EPS & 4x PCIe connectors
+
Build quality
+
Warranty

Cons

-
Expensive
-
OCP at 5VSB
-
Distance between peripheral connectors
-
Not top-notch transient performance
-
Inrush current with 230V input

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Features & Specifications

Seasonic recently announced the Prime Ultra series, which will eventually replace most of its vanilla Prime PSUs. The biggest difference between them is the newer line-up's more relaxed fan profile. Naturally, that helps reduce noise output.

But even as the Prime Ultras displace many overlapping Prime power supplies, Seasonic intends to keep some of its newer Prime models around. We think this is going to create confusion. The company should phase out the Prime name altogether and start transitioning to Prime Ultra across the board. But Seaconic's marketing department seems to disagree. Moving forward, then, there will be three Prime models: two 1300W PSUs and one 600W version without a fan. That's the power supply we're reviewing today.

For reference, the table below shows the major differences between older Primes and the new Prime Ultras.

As you can see, only the Prime series includes a fanless model. Beyond their relaxed fan profile, the Prime Ultras don't employ in-line capacitors on their modular cables, they include a tester for jump-starting the PSU without the motherboard's help, they come with a SATA 3.3 adapter and flexible SATA connectors, and most Prime Ultras feature compact dimensions, measuring just 14cm-deep.

Seasonic's Prime Fanless 600W (or SSR-600TL) is currently the highest-capacity fanless PSU you can buy. Thanks to high efficiency (80 PLUS Titanium and ETA-A+ in the Cybenetics program), it has low energy losses, allowing it deliver more power without a need for active cooling components. A power output of 600W under tough operating conditions, without a cooling fan, is an impressive achievement indeed. Really, it showcases the true capabilities of Seasonic's Prime platform, currently considered the best analog platform out there. The Prime design is so good, we've found, that in some disciplines it even challenges fully digital platforms. After so many years in the field, Seasonic's engineers are able to push analog circuits at levels that were once thought out of reach.

Specifications

The SSR-600TL's $190 price tag is high. Then again, that's the case for all fanless PSUs, which typically command a premium. As mentioned, this model boasts high-end efficiency certifications from 80 PLUS and Cybenetics, is fully modular, and sports a maximum operating temperature of 50°C, indicating that it's able to cope with tough operating conditions.

Seasonic arms this fanless PSU with a complete suite of protection features. The lack of a cooling fan might even benefit its reliability over time, since active components are often the ones that wear out and cause failures.

Power Specifications

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Rail	3.3V	5V	12V	5VSB	-12V
Max. Power	Amps	20	20	50	2.5	0.3
Watts	100	600	12.5	3.6
Total Max. Power (W)	600

The minor rails aren't particularly strong, offering up to 100W of combined power. Fortunately, modern systems only utilize the 5V and 3.3V rails lightly. Conversely, the +12V rail is plenty capable with a 50A maximum current output rating. Seasonic's 5VSB rail has a fairly typical capacity.

Cables & Connectors

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Modular Cables
Description	Cable Count	Connector Count (Total)	Gauge	In Cable Capacitors
ATX connector 20+4 pin (600mm)	1	1	18-22AWG	Yes
4+4 pin EPS12V (650mm)	2	2	18AWG	No
6+2 pin PCIe (680mm+80mm)	2	4	18AWG	No
SATA (450mm+110mm+110mm+110mm)	1	4	18AWG	No
SATA (350mm+110mm)	1	2	18AWG	No
Four-pin Molex (450mm+120mm+120mm)	1	3	18AWG	No
Four-pin Molex (350mm+120mm)	1	2	18AWG	No
AC Power Cord (1350mm) - C13 coupler	1	1	18AWG	-

At long last, we have a passive PSU with two EPS connectors and four PCIe ones. The number of peripheral connectors is high as well, given this model's efficiency. Cable length is adequate, though we would like to see 15cm between the peripheral connectors.