The PSU has an output power of 550W and can provide 492W across its +12V rail. In fact, the 100W addition relative to the VX450W refers to the +12V rail. That’s okay because it is the +12V rail that powers all the heavy consumers of a modern PC system such as processor, graphics card, etc.
The PSU doesn’t have “virtual” +12V output lines with current limiters. The maximum current of 41A is declared for the whole +12V rail.
The PSU is equipped with the following cables and connectors:
- Mainboard cable with a 20+4-pin connector (60cm long)
- CPU cable with a 4+4-pin connector (60cm)
- Graphics card cable with a 6-pin connector (60cm)
- Graphics card cable with a 6+2-pin connector (60cm)
- Two cables with three Molex connectors and one floppy-drive plug on each (40+14+14+14cm)
- Two cables with three SATA power connectors on each (45+15+15cm)
The selection of cables has become richer in comparison with the VX450W: there is now a second graphics card cable with a 6+2-pin connector (the 2-pin part is detachable, so this cable can go into both 6-pin and 8-pin connectors of graphics cards). Therefore you can connect either one top-end or two mainstream graphics cards to the VX550W without any adapters.
The cables and connectors have the same design as those of the VX450W: the cables are sleeved, the SATA connectors are T-shaped in the middle of a cable and straight at the end, the Molex connectors are straight but short, without rubber casings or anything.
The PSU worked normally at any load it is rated for.
The output voltage ripple on the main power rails is twice or thrice lower than the permissible limits. There are no short spikes, either.
The cross-load diagram of this PSU is perfect. None of the three voltages deflects more than 3% from their nominal values at any load distribution, and the +5V and +12V rails always keep within a 2% deflection even! Although I wrote above that the results of the VX450W are quite normal and you won’t have problems with it in a modern PC, the results of the VX550W are impressive nonetheless. With minor differences in circuit design, the senior model ensures stable operation in every mode it is supposed to support without any reservations.
The PSU is somewhat less efficient than the 450W model, especially at very low loads. The difference isn’t big, though. This model reaches an efficiency of 80% at about 100W.
The two PSUs differ more in terms of noisiness. The senior model is somewhat noisier due to the more powerful fan and different algorithm of the fan speed adjustment. The fan is rotating at 930rpm at loads up to 200W, which is somewhat higher than the fan speed of the VX450W. Anyway, this is still quiet enough.
But then the fan accelerates rapidly reaching its maximum speed at a load of 400W (150W below the maximum load). The VX450W had a fan speed of 1800rpm at such a load. Here, the fan speed is 2200rpm.
So, the VX450W and VX550W belong to the same series but have more differences than just their wattage ratings. The VX550W has two graphics card cables, which are going to come in handy for such cards as the single-chip GeForce 9800 GTX or the dual-chip GeForce 9800 GX2 and Radeon HD 3870 X2, and delivers ideally stable voltages at any loads. On the other hand, the VX450W is somewhat quieter in every mode, both at low and maximum loads, so you may want to prefer it if you are not going to assemble a particularly advanced computer configuration.