Cooler Master Real Power 550

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Feature Highlights of the Cooler Master Real Power 550 RS-550-ACLY


Compliance with the newest Intel standard ATX12V v2.01 and the newest SSI standard EPS12V v2.1

No longer the newest of either standard, but changes to the newer revisions are minor.

Super silent operation with intelligent fan speed control (<23dBA)

We measured the 450W model at 23 dBA/1m. Can the 550W match this number?

Power consumption management by human computer interface (HCI)

I'd call it monitoring, not management. Use Cool 'n' Quiet if you really want power management.

PCIe connector satisfy high end graphic card requirement

Almost mandatory on power supplies of this size.
Support +12V1, +12V2 and + 12V3 outputs for higher power usage
In compliance with the EPS12V requirements.

Green power design to meet energy star and blue angel requirement

A guaranteed maximum power draw in standby, but these certifications do not address efficiency at idle or load.
More than 75% efficiency at typical load operation A conservative claim. Most modern PSUs can do better than this, including Cooler Master's 450W version.
Higher reliability (MTBF > 400,000 hours) Eight times the EPS12V recommended MTBF.
OVP / OCP / OTP / OLP / Short / Full protection All the usuals plus over temperature protection.
Active power factor correction (PF > 0.99) Required by EPS12V, but uncommon on ATX12V power supplies.
Real power capacity satisfy high-end system operation More than enough room for any desktop system.

The Real Power is aptly named: It is rated more realistically — make that honestly — than most other power supplies on the market. Both the peak and the continuous output capacities are specified. The majority of power supplies list only their peak capacity, but cannot deliver their rated capacity indefinitely.

The peak ratings of the Real Power are in line with the ratings of other power supplies of this capacity: 30A apiece on the +3.3V and +5V rails and close to 20A on each of the +12V rails. In fact, the additional +12V3 rail puts the combined +12V rating at a whopping (and completely unnecessary) 48A. If the Real Power was rated in the way that most other power supplies are rated, it would be sold as a 650W power supply. However, Cooler Master's decision to rate it properly drops its capacity down to "only" 550W.

The more reasonable continuous ratings put the combined +12V amperage at 30A, which is still a very hefty rating. It is almost impossible to think of a combination of components that actually requires this amount of power.

SPECIFICATIONS: Cooler Master Real Power 550 RS-550-ACLY

AC Input

90-264V @ 47-63 Hz

DC Output








Peak Output Current








Continuous Output Current








Continuous Output Capacity


Peak Output Capacity


The trio of +12V rails are specified by the EPS12V form factor, and deserve a little explanation for those who are only familiar with ATX12V. Like ATX12V, the CPU is isolated from the rest of the system on its own +12V rail (+12V1). In addition, the motherboard and workstation connector (+12V2) are separated from the rest of the peripherals (+12V3), which usually means the drives. This allows a large number of drives to be spun up simultaneously without starving either the CPU(s) or a powerful video card for power.

It's not entirely clear how this three-rail EPS12V design is adapted to meet the ATX12V specifications. Neither the 4-pin Auxiliary ATX connector nor the PCIe connector are a part of EPS12V, so the specific rails for these connectors are unknown. However, so long as these connectors are kept on separate rails there should be no problems. The most logical and most likely configuration would be to put the Auxiliary ATX connector on +12V1 and the PCIe connector on +12V2. This would keep the two connectors isolated from each other while still keeping the weaker +12V3 line free to power any drives.

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