On Fri, 27 Jul 2018 12:22:08 +0300
> There is no any external hub or cable between AR9271 usb stick. I > attach it directly to AMD GX-420CA SOC with Radeon(tm) HD Graphics > PC. Firmware does not load when it attached to any of USB2.0 ports. > But when it attached to USB3.0 AR9271 works without any errors. USB3 provides more current than USB2, so this may make sense with the current theory of some USB2 boards not supplying enough power for these devices. USB has to protect against user insertion, damaged ports etc. so surges are filtered more so than required for USB via pci-ex. I wonder if the firmware loading speed can be dialed down so that less power is required (perhaps it saves memory by verifying as received) or more likely the issue occurs after upload completion? Is the open firmware a different size or sets different power settings? Are any power affecting settings available before firmware upload? If the power usage is close to the limit then it may cause micro reset/failure a varying percentage of the time. Sorry if all this has already been considered.
