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Corsair CX650M PSU Review

Corsair's CX series consists of both non-modular and semi-modular units. It was recently upgraded with new members and improved versions of older ones. The CX650M is the third strongest member of the line, featuring 650W capacity and a 40°C rating.

Transient Response Tests

Advanced Transient Response Tests

For details on our transient response testing, please click here.

Ιn these tests, we monitor the CX650M's response in two different scenarios. First, a transient load (10 A at +12V, 5 A at 5V, 5 A at 3.3V, and 0.5 A at 5VSB) is applied for 200ms while the PSU works at 20 percent load. In the second scenario, the CX650M is hit by the same transient load while operating at 50 percent load. In both tests we use our oscilloscope to measure the voltage drops caused by the transient load. The voltages should remain within the ATX specification's regulation limits.

These tests are crucial because they simulate the transient loads a PSU is likely to handle (such as booting a RAID array or an instant 100 percent load of CPU/GPUs). We call these tests "Advanced Transient Response Tests," and they are designed to be very tough to master, especially for a PSU with a capacity of less than 500W.  

Advanced Transient Response at 20 Percent

VoltageBeforeAfterChangePass/Fail
12V12.094V11.938V1.29%Pass
5V5.021V4.966V1.10%Pass
3.3V3.287V3.185V3.10%Pass
5VSB5.066V5.030V0.71%Pass

Advanced Transient Response at 50 Percent

VoltageBeforeAfterChangePass/Fail
12V12.048V11.893V1.29%Pass
5V5.007V4.952V1.10%Pass
3.3V3.276V3.157V3.63%Pass
5VSB5.030V5.001V0.58%Pass
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It would be nice if the +12V deviations stayed within 1%, but we can't be that picky with such an affordable PSU. The 5V and 5VSB rails have low deviations, while 3.3V registers the worst performance. In both tests the 3.3V rail drops its voltage below 3.2 V as soon as the transient load is applied.

Here are the oscilloscope screenshots we took during Advanced Transient Response Testing:

Transient Response At 20 Percent Load

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Transient Response At 50 Percent Load

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Turn-On Transient Tests

In the next set of tests, we measure the PSU's response in simpler transient load scenarios—during its power-on phase.

For the first measurement, we turn off the PSU, dial in the maximum current the 5VSB can output, and switch it back on. In the second test, we dial the maximum load the +12V rail can handle and start the PSU while it's in standby mode. In the last test, while the CX650M is completely switched off, we dial the maximum load the +12V rail can handle before switching the PSU on from the loader and restoring power. The ATX specification states that recorded spikes on all rails should not exceed 10 percent of their nominal values (+10 percent for 12V is 13.2 V, and 5.5 V for 5V).    

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The 5VSB slope is perfect. The +12V slopes are pretty good as well, with the last one featuring a very brief period of increased ripple. That's nothing to worry about, though.

  • Dark Lord of Tech
    Thanks for the review on this new CXM platform.
    Reply
  • JQB45
    Looks to be better then the old CX line up.
    Reply
  • Onus
    Good to see that Corsair didn't produce a Turkey with this one.
    Reply
  • turkey3_scratch
    Onus why would Corsair produce me?

    Anyway I think the price/performance page shows all. This thing rocks!

    Also Jonnyguru claims it is a rifle bearing fan that has the same model # as the sleeve variant.
    Reply
  • benedict78
    Does the CX650 perform the same as the CX650M? I'm not interested in modularity anyway.
    Reply
  • turkey3_scratch
    The CX650 is not out yet.
    Reply
  • Aris_Mp
    I have several CM and CX-M units, which I plan to fully evaluate. So far I figured that there are differences (something natural of course) in their performance.
    Reply
  • Dark Lord of Tech
    Could you put the newer CXM 750W OR 850W on deck soon , as they are widely use for DUAL CARD configurations.
    Reply
  • turkey3_scratch
    The 750W and 850W CXM units are basically unchanged except for a bridge rectifier upgrade. Everything else is the same. Only the CX450-650M got the major revisions.
    Reply
  • Dark Lord of Tech
    Yeah I know that , but want to see one reviewed , to compare top older generations.
    Reply