Failure observed for USB3.2 Gen 1 5Gbps loopback test

[SIng Yew Chan]

Hi Passmark team,

I observed quite a number of read errors and link errors when running the loopback test on one of the USB3.2 Gen2 type A port.
You may refer the loopback log file as attached.(opps, seem like i am not allowed to upload the txt file)




Could you guys help to analyze what errors it related to ?

[David (PassMark)]

Typically this is hardware failure of some sort.
Bad cable shielding, cable too long, bad electrical connection on the socket, etc..
These type of things also appear more often on the front ports of PC cases as there are extra internal cables, so the signal quality is worse.

Smaller chance it could be a device driver bug or load issues as well.

[SIng Yew Chan]

Hi David,

Could I understand more on the loopback test performed by using the Passmark loopback plug.
Based on the understanding from the log, it seem like there is a buffer at the loopback plug.

When the predetermined data transferred from the host (laptop) to the loopback plug, if there is any error occurred, it will treat it as write error ?
When the data transferred back from the buffer(loopback plug) to the host (laptop), if there is any error occurred, it will treat it as read error ?

Basically, i am curious how will it know they are any write errors or read errors as I am trying to find out the SI issue potentially coming from TX or RX lanes.

Besides that, I also get the USB3 trace using protocol analyzer and I couldn't observe any obvious error in the trace.

Regards,
Jason

[David (PassMark)]

seem like i am not allowed to upload the txt file

Text files of up to 2MB can be attached to a post.

it seem like there is a buffer at the loopback plug

All USB devices have a buffer, at least one big enough for a packet of data.

if there is any error occurred, it will treat it as write error

There are dozens of different errors possible. Errors in Windows itself, errors in the host controller device driver, link layer errors and physical errors. For the last to you can find a summary on this page
https://www.passmark.com/support/usb3loopback_faq.php

But generally speaking, most errors encountered while trying to send data will result in a write error. And most errors encountered while trying to read data from the plug will result in a read error.

The plug can also send error information to the host. So if the plug failed to read the data from the host, it can send an error indication back to the Windows software.

To really get to the bottom of issues like this you need to both,
1) Do some trial and error (different USB ports, different cables, different settings, different plug, different laptop) to narrow down the problem
2) Get a protocol analyser. The "Beagle USB 5000" is a good choice.