Cooler Master 550W "Real Power" Power Supply

Interior of the CM 550W Real Power:

The inside of this power supply is really packed with components. Instead of a single main transformer there are two (as shown in the picture below), plus a smaller one (presumably for -12V & 5Vsb) hidden underneath an air duct (it's above the transformer in the center). The brown wire in the top-left area I believe is part of power meter setup, the wire loops through a sensor that detects the amount of current passing through it. Overall the design & assembly is really quite nice. There are a couple pots well hidden from plain sight (presumably for voltage adjustment), so it may be possible to fine-tune the rails for your PC setup. Opening up a power supply is dangerous and will void your warranty, any risk is assumed by you.

Curious about having three 12V rails, and wanting to figure out which connector was on which rail, I pulled the PCB out of the chassis and took a look for myself. I came to discover (and Cooler Master confirmed this) that 12V1 & 12V3 are connected together as one output at the PCB, and 12V2 as another output. This was done as a compromise between EPS12V & ATX12V standards to allow maximum utilization. The logic is that there are a couple EPS specific connectors which are not on ATX motherboards, thus one of the 12V rails would have been completely unused on consumer level ATX motherboards. Don't worry, this PSU still meets all UL and other safety requirements (they were even nice enough to send me a PDF copy the signed approvals). The design still fully conforms to the ATX12V v2.01 guidelines with the split 12V rail usage.

In reality you could say this PSU was designed to conform more to ATX12V v2.01 specs, with the enhanced power output (and connectors) for EPS12V v2.1 requirements, so you get the best of both worlds. The connectors are wired up properly as per ATX12V v2.01 guidelines and are as follows:

• 12V1 + 12V3
  • Main Power (24pin)
  • SATA Power
  • PCI Express (6pin)
  • Peripherals (4pin & floppy).
• 12V2
  • ATX +12V (4pin)
  • EPS Processor Power (8pin)
  • EPS Workstation (6pin).