Gigabyte P550B Power Supply Review

An affordable PSU with mediocre performance.

Gigabyte P550B
(Image: © Tom's Hardware)

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Protection Features

Check out our PSUs 101 article to learn more about PSU protection features.

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OCP (Cold @ 27°C)12V: 47A (108.05%), 11.532V
5V*:19.6A (130.67%), 4.690V
3.3V*: 26.5A (147.22%), 3.265V
5VSB: 4.8A (160%), 4.963V
*Tested with 2A at 12V
OCP (Hot @ 32°C)12V: 46.4A (106.67%), 11.534V 5V*: 20.3A (135.33%), 4.679V 3.3V*: 26.6A (147.78%), 3.266V 5VSB: 4.7A (156.67%), 4.967V *Tested with 2A at 12V

OPP (Cold @ 27°C)

653.81W (118.87%)

OPP (Hot @ 35°C)

641.77W (116.68%)


✗ (>200°C @ 12V Heat Sink)


12V to Earth: ✓
5V to Earth: ✓
3.3V to Earth: ✓
5VSB to Earth: ✓
-12V to Earth: ✓


Accurate but lower than 16ms



Surge: MOV
Inrush: NTC Thermistor

MEIC was wise enough to set OCP on all rails, but 3.3V, at low levels since the bridge rectifier and the rest parts would have a problem keeping up under high loads and with low voltage input. OPP is set reasonable set, as well. 

The 3.3V rail requires OCP tuning to quickly kill the PSU under such high loads and increased operating temperatures.

A major downside here is the lack of Over Temperature Protection (OTP). This protection is essential to any power supply, especially the low-end ones. 

DC Power Sequencing

According to Intel’s most recent Power Supply Design Guide (revision 1.4), the +12V and 5V outputs must be equal to or greater than the 3.3V rail at all times. Unfortunately, Intel doesn't mention why it is so important to always keep the 3.3V rail's voltage lower than the levels of the other two outputs.

The 3.3V rail is very close to 5V, as you can see in the scope screenshots above. Nonetheless, it doesn't go above the 5V rail's level, so it aligns with the ATX spec requirements. 

Cross Load Tests

To generate the following charts, we set our loaders to auto mode through custom-made software before trying more than 25,000 possible load combinations with the +12V, 5V, and 3.3V rails. The deviations in each of the charts below are calculated by taking the nominal values of the rails (12V, 5V, and 3.3V) as point zero. The ambient temperature during testing was between 30 to 32 degrees Celsius (86 to 89.6 degrees Fahrenheit).

Load Regulation Charts

Efficiency Graph

(Image credit: Tom's Hardware)

Ripple Graphs

The lower the power supply's ripple, the more stable the system will be and less stress will also be applied to its components.

Infrared Images

We apply a half-load for 10 minutes with the PSU's top cover and cooling fan removed before taking photos with a modified FLIR E4 camera able to deliver an IR resolution of 320x240 (76,800 pixels).

The secondary side gets quite hot, without any active cooling. The coils on the secondary side also get hot, and these are close to the low-quality filtering caps, so without good cooling, this platform will soon depart from this world. This is why it needs such a strong airflow, and this also explains the PSU’s high average noise output. 

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Contributing Editor

Aris Mpitziopoulos is a Contributing Editor at Tom's Hardware US, covering PSUs.

  • refillable
    Nice one Aris! I have a request for you. Can you test the Seasonic S12III? It has been circulating around a year now and no one seems to be bothered testing it.
  • Aris_Mp
    If I manage to find one, suree!
  • NightHawkRMX
    I second this request for the S12iii. Given the popularity of the S12ii (at least back in the day), I am interested to see a review of the successor. I think the fact its RSY made kind of adds to my interest.
  • NightHawkRMX
    Gigabyte GP-P750GM 750 W Review - With an Explosive Attitude | TechPowerUp
    Well, at least it did not explode.

    Gigabyte should just be banned from making PSUs at this point.
  • Aris_Mp
    NightHawkRMX said:
    Gigabyte GP-P750GM 750 W Review - With an Explosive Attitude | TechPowerUpWell, at least it did not explode.

    Gigabyte should just be banned from making PSUs at this point.
    Yes this one didn't treat me with fireworks :)