B850M Pro-A Shutdown issue
Printed From: ASRock.com
Category: Technical Support
Forum Name: AMD Motherboards
Forum Description: Question about ASRock AMD motherboards
URL: https://forum.asrock.com/forum_posts.asp?TID=113284
Printed Date: 07 Aug 2025 at 10:35pm
Software Version: Web Wiz Forums 12.04 - http://www.webwizforums.com
Topic: B850M Pro-A Shutdown issue
Posted By: brigitta
Subject: B850M Pro-A Shutdown issue
Date Posted: 07 Aug 2025 at 4:39am
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My ASrock B850M Pro-A with Ryzen 5 7600X suddenly started to reboot after shutting down by the OS. I am running Manjaro Linux, latest. First I tried to power down the system by "sudo poweroff" or by "sudo shutdown -h now" instead of the GUI button. But it kept rebooting. Then I watched precisely, at what stage the computer would turn on again and I found out, that the OS is already finished, the fans and the harddisk start to spin down and then the restart happens. I have checked all BIOS items, which could wake up the computer like PCI or LAN etc. but I did not find any setting, which would cause the reboot. Searching the web, I found the hint, that sometimes a PSU could be the cause. But my PSU is a 350 W bequiet! PSU which formerly was used in my older computer, having a total operating time of about 500 hours only. The PSU was never causing any problems. How can I find out the reason for auto-rebooting after shut down? |
Replies:
Posted By: Xaltar
Date Posted: 07 Aug 2025 at 3:38pm
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PSUs can degrade over time and should always be viewed as a possible issue. I have often seen even new PSUs end up being the cause of issues. It's one of the first components that needs to be ruled out during troubleshooting most problems. If you have a means to, try the system with another PSU and see if it resolves the issue. As a side note, I have never been a fan of BeQuiet PSUs, there have been a disproportionately large number of them reported as defective here on the forums over the years. It's not because they are a bad brand but because most of their units are dual rail which require a little more know how when building. The power draw needs to be balanced across both 12v rails or one of the rails ends up overloaded. This is especially true for their sub 600w units. Your unit is no exception, it has 2 12v rails that are only rated at 18A. Essentially, if all the load is on a single 12v rail then you are effectively only using a ~175 watt PSU. In fact, I suspect the PSU may not like being loaded in this way on more than one level, it could well be the cause of your issue. Try identifying your 12v rails and make sure you are distributing the load properly. Determine which rail provides power to the 24pin power connector then use the other 12v rail to provide power to the 8pin CPU power. You can simply swap the 8pin CPU power for the other rail and see if that helps the situation. They should be labeled 12v1 and 12v2 on the unit itself or in it's manual. ------------- 
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Posted By: brigitta
Date Posted: 07 Aug 2025 at 6:20pm
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Thank you for your advice. It is not possible to swap the 12 V plugs, because bequiet! has assembled the both lines with multiple wires in parallel in separate plastic shields. I would have to separate these which is hardly possible. I have used the 24-pin power plug and its 4-pin extension as well as the additional 8-pin plug for 12 V at the top side of the board. But I had no additional 12 V plug available from the PSU to connect to the additional 4-pin 12 V plug at the top side of the board. Could this be the cause for the failure, that I have no additional 12 V supply at this 4-pin 12 V connector? There is a warning in the board manual, to NOT connect a possible available 12 V VGA plug to the 12 V 4-pin-connector at the top side of the board. I have respected this warning. But would this VGA 12 V plug be the 12 V output of "the second rail" you have mentioned? I have another PSU which can deliver 550 W (sorry but it is also manufactured by bequiet!) and I will try this. It has the additional 12 V plug, so that I can supply all 12 V connectors of my board. I will report here again about the results. |
Posted By: Xaltar
Date Posted: 07 Aug 2025 at 10:19pm
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You only need to connect a single 4pin to CPU power on the board. A single 8pin is preferable however. The second 8pin socket is typically only used by power users for overclocking or when the board is fully populated with high power devices. So no, not connecting the additional 4pin 12v is not the cause. If BeQuiet wired your PSU in parallel then the load should be balanced. The problem is that parallel 175w = 175w not 350w. This is why I don't like BeQuiet, their marketing and specs are wildly misleading. Try the 550w unit, I suspect that may resolve your issue. -------------
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