USB 2 disconnections on B550M MORTAR and Ryzen 5 5600x (Zen 3)

GreyFox

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Nov 28, 2020
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Hello,

I'm getting random disconnections of devices connected to internal and external USB2 ports on my B550M MORTAR WiFi mobo and Ryzen 5 5600x system.
System runs flawlessly and no issue happens with USB 3 devices. I was able to move my peripherals on my USB3 ports, but some internal components (such as my AIO, my power supply unit) all have USB2 internal header connections, and these keep happening. All devices will disconnect then reconnect in a second. I was able to clearly spot this using USBLogView from Nirsoft (www.nirsoft.net)

I've opened a ticket with MSI support, which tells me to initiate an RMA. Given that this is a new motherboard received a few days ago from Amazon, I would probably just swap to another one then. The issue, is that I was coming from a Gigabyte B550M AORUS PRO-P motherboard which was also showing USB 2 connectivity issues.

Note: running on the latest non-beta BIOS available on the board support page.
Version
7C94v14
Release Date
2020-11-04

Is anyone else running in issues with USB 2 devices and their Zen 3 CPU and this motherboard?
 

graycorgi

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Dec 25, 2011
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Similar problem on MSI X570 Tomahawk and 5900X. My Corsair headset drops audio often when the system is under load unless I use a USB 3.0 port. My AIO also occasionally disconnects and reconnects (maybe once every couple days) - it's connected to an internal USB 2.0 header. Seems to be a lot of people with X570 / B550 boards from various vendors having this problem to some degree with Zen 3 CPUs.
 

graycorgi

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Dec 25, 2011
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I was able to "Solve" my specific problem by forcing PCIe to Gen 3 even though this will lose some performance. Not sure if that will solve it for everyone else, but it is apparently a widespread issue. If you google PCIE 4.0 USB 2.0 Stuttering there are tons of results dating back to a year ago with multiple board vendors. I guess not enough people have reported the problem for it to be fixed.
 

GroundRod

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Dec 6, 2020
Messages
378
Is your system grounded properly?
Is your wall outlet wired properly?
Have you tested the outlet?
Check screws for power supply for continuity to the case, the paint on the case can insulate the case and screws from making a solid electrical connection of the PSU to the case.


Cheers
 

graycorgi

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Disabling Global C states did not fix it for me. It was the first thing I tried since a popular youtuber suggested it. The only thing that has fixed it for me is manually setting PCIe to 3.0.

And yes my system is grounded properly, my outlet is wired properly, the outlet is fine, the power supply is fine, none of that changed at all from my old Z370 board which had none of these issues. Based on the volume of people reporting the issue and the fact that I have a really nice power supply, I'm extremely doubtful this would be a power issue.

Here are a few reports of this issue (one of which dates back a full year!). There's tons more I could link too, it seems to be fairly widespread. Since there have not been a lot of people using PCIe 4.0 GPUs it has probably been under-reported.
https://www.reddit.com/r/AMDHelp/comments/e598ho https://www.reddit.com/r/MSI_Gaming/comments/k026eo/_/ge8q5bo
 

graycorgi

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Dec 25, 2011
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Did disabling Global C states fix it for you? If so, then yes that's the issue they're talking about in that thread.
 

GroundRod

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Dec 6, 2020
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Excluding the mouse, keyboard, and monitor disconnect everything else and try the usb device again and see if that works.
 

GroundRod

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Dec 6, 2020
Messages
378
Most powered USB devices are not grounded and can cause a ground loop.
One trick that sometimes works is to reverse the AC plug, and if that fails, you would have to mod it.
 

GreyFox

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Nov 28, 2020
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What USB devices are you using?
I have already listed the USB2 devices (being AIO and PSU). This also does not change regardless of the number of devices connected, nor which devices. So again, I don’t see how this can be a grounding problem.
 

GroundRod

Master Builder
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Dec 6, 2020
Messages
378
I have already listed the USB2 devices (being AIO and PSU). This also does not change regardless of the number of devices connected, nor which devices. So again, I don’t see how this can be a grounding problem.
Clearly your upset and I can understand how frustrating it can be when something is not working, but I look at these problems as an opportunity to learn, and not get mad.
Just so you know, I am an electronics engineer with 40 years of experience at the component level, with both analog and digital circuits and have built many computer systems.
From your description, this problem seems to be very obscure and PCIe4 is working for 99.9%, so the cause, in my opinion might be a build issue.

Can you please tell me what case you are using?
 
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