USB Port Unit Bandwidth and datasheet typo? (Solved)

Autonomous Machines Jetson & Embedded Systems Jetson AGX Xavier
1

Hello,

I have five USB 3.0 devices that ideally, can operate at full bandwidth with the Xavier. The Xavier has 3 available USB 3.1 ports (P0, P2, P3). The datasheet in section 1.9.3.3 says “USB 3.1 port 0 and port 3 share one 10Gbps unit bandwidth, while USB 3.1 is allocated a separate 10Gbps unit bandwidth.”

  1. It looks like there is a typo in the datasheet. I assume it is saying port 2 is allocated a separate 10Gpbs unit bandwidth. Is this correct?

  2. What does it mean that port 0 and port 3 share one 10Gpbs unit bandwidth? Do these ports effectively go into a USB hub on the Xavier?

  3. If I put one USB 3.0 device at 5Gpbs on port 0 and another 3.0 device at 5Gpbs on port 3, can both devices send their full bandwidth data to the Xavier? Or would their data rates be halved like you would expect if they both routed through a USB hub?

Thanks!

2

We need to update the technical manual with all these details, great.

3

Sorry, are you suggesting that the answers are not known at this time?

4

I have similar questions about this. Are there any updates?

5

Hi guys, we are looking into what the correct wording in the datasheet is. Please stay tuned.

6

Great, thanks for letting us know. Please note that the typo isn’t my main concern. Questions (2) and (3) are driving my engineering decisions. Thanks!

7

Hi mark2,

Due to throughput limitations in the xHCI controller, USB 3.1 port 0 and port 3 share 10 Gbps total bandwidth, while USB 3.1 port 2 has the full 10 Gbps total bandwidth.

In case of two SuperSpeed devices connected to the same SuperSpeedPlus hub, which in term connects to a XUSB host port, due to scheduling policy reasons, each SuperSpeed device may not be able to be supported with full SuperSpeed unit bandwidth.