Jump to content
Corsair Community

CX series, 3.3 V droop/noise @ low power load, NVMe SSD Disappears from BIOS


Recommended Posts

Built 4 systems with:

Motherboard: ASUS PRIME H270-PRO

CPU: Intel i7-7700 w/ CoolMaster Hyper Series 212 EVO

Storage: Samsung M.2 NVMe SSD 960 PRO 512 GB, MZ-V6P512

Memory: Kingston HyperX Savage DDR4 2400MHz 2x8GB HX424C12SB2K2/16

Power Supply: Corsair CX500


Office PCs in engineering environment running Office suites and computer simulations, computationaly demanding, not graphic. For graphically demanding application, will add discrete GPU as necessary.


All 4 have issue, randomly, every so often, upon restart or cold boot NVMe SSD is not seen by BIOS. System will not run.


Samsung took one entire system and debugged, found 3.3 V supply on Corsair CX500 PSU experiencing significant noise and droop, causing issue with signals to NVMe SSD on PCIe bus. As result, BIOS could not initialize SSD. Samsung replaced PSU with their test model and system worked fine, 3.3 V was reliable.


Further study finds 3.3 V has problem when overall power drawn through PSU is <~27 W. As there are few components in this system (MB, RAM, SSD) the overall power draw can be low. Typically, sitting idle, with a watt (power) meter at the AC input of the PSU, can measure 22-23 W. In this state, the 12 V and 5 V rails look very good, at proper voltages, little noise. 3.3 V supply has hundreds of mV of noise and droop, way outside spec. Adding load to the 12 V rail (25 ohms, or ~500 mA added load, ~6 W), bringing power drawn at AC input to ~27-30 W brings 3.3 V supply into proper operation, proper voltage, very little noise.


Operating with this added load, system ran reliably for >24 hrs (cycling restarts every 5 minutes), where before issue would present every half to one hour.


Also tried using CX430 PSU, exact same observations.


One might be inclined to say CX430/500 PSU is not confirmed for Haswell compatibility, low power C6/C7 states, and thus shouldn't be expected to operate under this low/reduced load. But, this is normal operation not like the C6/C7 states. Specifically, this occurs upon start up well before any power reduction schemes are implemented. And, the C6/C7 compatibility issue has to do with the reduced load drawn on the 12 V supply rail that may cause it to lose regulation. In this case, the 12 V and 5 V are solid, but the 3.3 V is having the issue.


Corsair support is reviewing issue through RMA channel.


A VERY simple estimate of the maximum power consumption for this system might be 65 W CPU, 3 W CPU Fan, 20-30 W MB, 7 W NVMe SSD, 6 W RAM = ~113 W. When running PassMark BurnInTest with several components set to 100% it measures ~100 W. Running Prime95 max is ~135 W.


So, the range of operating power for this system is 20 W to 135 W. If, a mid-range discrete GPU were added the maximum power may be on the order of 300 W.


The CX series PSUs have served us well over many years (we have 10+ in service), providing quiet operation, good power factor, reasonable efficiency, not a single issue, all at a reasonable price.


Should the CX work under this lower power application, or are there recommendations that will operating under low/light loads?


Other threads with same experience:

"CX430 can't handle the 3.3v line under low load", http://forum.corsair.com/v3/showthread.php?t=167908

"CX500 - Too Little Load or Bad Unit?", http://forum.corsair.com/v3/showthread.php?t=95283

Link to comment
Share on other sites


This topic is now archived and is closed to further replies.

  • Create New...