jwillis84

This thread looks almost a year old. But chiming in here. The assumption here is that the [boot order] could be resequenced to included a [Hot plug] device in BIOS.. probably never gonna happen. Current USB PXE support depends on the inclusion of a device driver in the BIOS for a specific USB device. The BIOS writers then allocate and make room for that specific device in the boot order if it is present [on power up]. It "appears" hot plug, but in reality the bus is not reenumerated so technically "appearences can be deceiving".. it is definitely "not" hot plug. It is "convience plug" -- if it happens to be plugged in "before" power up it will be added to the boot order. If you have access to a BIOS update and can uncompress and list the "modules" included in the BIOS you "may" find some device driver names that look familar. This is not "hacking" the BIOS or decoding or anything spectacular.. its just looking under the hood to see whats supported because currently BIOS distributors don't really document what they put into the BIOS in the way of firmware drivers very often. Its left to marketing to pickup up on "new sales features". The "Change Log" for a new BIOS update is the most common accidental way of discovering new USB to Network chipset support... and they are "not" Universal at all. Smsc (Smart Mixed-Signal Connectivity, Inc.) for example seems to be a popular device driver to include, after American Megatrends announced a tighter integration with Smsc and then Microchip acquired them in 2012. They also make reference code for a BIOS PXE UNDI driver freely available which tends to wind up in many BIOSs. The same driver for LAN7500 works for the LAN9500 chipset which appears as an Smsc device. As far as I know the StarTech USB21000S2 is the most common Smsc USB2.0 to NIC dongle available. But will only work if your BIOS includes the driver. The LAN9500 chipset tends to wind up in Laptop and Tablet Docks which means its far more common for PXE to work for a Laptop or Tablet -- while it is "Docked" -- than when using a generic USB to Network dongle. The BIOS would have a Smsc device driver and automatically add the Dock ethernet port to the boot order. StarTech and other Dongle manufacturers really have no way of knowing if their devices are PXE capable, because PXE is usually the domain of the boot order in the device BIOS. Anyone could add, remove, or accidentally enable or disable (if using secure boot with efi) the function. Realtek also has a Dongle chipset the RTL8153 which is a USB 3.0 to NIC chipset, IOcrest, Sybausa and Anker sell such a dongle. But its fairly new and unless the BIOS has been updated to include a device driver for this new chipset, it will not PXE boot. If it has been updated to include the device driver, like the Dell XPS 15 9530 BIOS apparently has.. then it should appear in the boot order and should PXE boot. Be forewarned! There are many, many - USB to Network dongles based on the ASIX chipsets, they are fairly pervasive.. and not many seem to be including a device driver in the BIOS for these [yet] some of the Tablets like the Dell Venue line appear to be [starting] to include device drivers for [some] of the ASIX chipsets.. but it is completely at the whim of the BIOS designer, vendor, ect.. BIOS tends to be highly specialized OS writing and has to fit a lot into a small space so they don't tend to include a lot of device drivers out of the box, or first release. There are also licensing issues to consider when embedding device drivers from hardware vendors. EFI bioses in "theory" will make things better eventually as there should be a flash memory space to "toss" EFI drivers to support additional dongles. But the recursive problem remains, out of box, straight from the factory.. how do you include the device driver to support your USB network device? Probably unless we get universal class drivers for everything.. the best that can be done is for BIOS makers to begin thoroughly documenting the device drivers included in each release.