The PSU can yield 744 out of its maximum 750 watts across the +12V power rail. This rail is monolithic, i.e. not split up into multiple "virtual" rails.
Cables and Connectors
The following cables are included with the PSU:
- Mainboard cable with a 20+4-pin connector (57 cm)
- CPU cable with a 4-pin connector (58 cm; it goes into the 4-pin connector of the PSU)
- CPU cable with an 8-pin connector (58 cm; it goes into the PSU’s 8-pin connector)
- CPU cable with an 8-pin connector (58 cm; for the PSU’s 12-pin connector)
- Two dual graphics card cables with two 6+2-pin connectors on each (58 cm)
- One cable with three PATA power connectors (55+15+15 cm)
- One cable with three PATA power connectors (45+15+15 cm)
- One cable with two PATA power connectors (35+15 cm)
- One cable with three SATA power connectors (45+16+16 cm)
- One cable with three SATA power connectors (55+16+16 cm)
- One cable with two SATA power connectors (35+15 cm)
- One adapter for two floppy drive plugs
This is a good selection of cables. There are as many as three different CPU power cables. And there are peripheral cables of different length.
Compatibility with UPSes
Working with my APC SmartUPS SC 620, this power supply was stable at loads up to 403 watts when powered by the mains and up to 375 watts when powered by the batteries. The pair switched the batteries normally; the UPS was stable.
Output Voltage Stability
Like any other model with dedicated DC-DC converters, the X-750 boasts near ideal output voltages. The voltage on the +5V rail is the only one to deflect more than 3% from the nominal value, but only at near-maximum loads.
Output Voltage Ripple
The output voltage ripple on the 12V rail can hardly be seen at all although its load is almost as high as 700 watts! The ripple on the +5V and +3.3V rails is only one half or one third of the allowable maximum.
Contrary to the current trend to use large fans, this PSU is cooled by a San Ace 120. As the name suggests, it is a 120mm model. The quality is high as the fan is manufactured by Sanyo Denki. Take note that it uses a 4-pin connection.
The fan did not rotate at all at loads up to 150 watts. And then it started up at a speed of only 200 RPM. The PSU was silent at loads up to 450 watts (900 RPM) and comfortable at 550 watts. At a load of 600 watts the fan accelerates to 1500 RPM and the noise of the air becomes rather loud. However, that was a uniform and not irritating sound, probably because the roomy interior of the PSU poses but a minimum of aerodynamic obstacles.
Efficiency and Power Factor
As promised by the manufacturer, the efficiency is very high, reaching a maximum of 92%. The PSU is more than 80% efficient even at a load of 50 watts or 7% of its max output power!
The standby source of the X-750 is rated for a current up to 3.0 amperes and copes with its job well.
Seasonic has come up with a very appealing power supply unit. While the M12D with DC-DC converters used to represent but minor modernization of a well-known series, the X-750 is a completely new model that differs in its interior design not only from other Seasonic products but also from other makers’ models. Featuring new technologies and a new component layout, this is a modern, high-quality, stable, efficient and quiet PSU.
And it looks like Enermax with its Revolution 85+ and MODU87+ has got a serious competitor. Seasonic won’t stop after releasing one or two premium-class models but wants to expand its X series with PSUs of different wattage ratings, ranging from 400 to 1200 watts and including fan-less models.
The X-750 is going to be a good choice for configurations with a quad-core processor and one top-end graphics card, especially if you want to have a quiet and stable computer. According to our measurements, even GeForce GTX 480 and Radeon HD 5970 cards consume less than 500 watts together with an overclocked Core i7-920 under more or less realistic load. The X-750 Gold is going to be one of the quietest components in such an advanced gaming machine!
In conclusion we would like to award Seasonic X-750 with our Ultimate Innovation title: