F10 Gets me into Setup/BIOS and gives be access to every BIOS
setting. I've fiddled with booting device settings, and a USB
choice isn't available with this Pegatron Violet3-GL8E
Look at the initial POST screen. If the POST screen doesn't show text,
then disable the BIOS splash screen. Some BIOS have an option to show a
graphical image, which covers the normal text display. Enter the BIOS
and see if it has any options to support no-graphics on the first screen.
Normally, in the text based BIOS display, first page of text, there are
two function keys mentioned near the bottom of the screen. One key,
gets you into BIOS setup. The second key, presents a BIOS "pop up boot menu".
In the pop up boot menu, you'll see hard drives, CD/DVD/drives, and also
USB flash sticks, that are plugged into the computer. You can select
a device there, and start booting.
On my current computer, <Del> enters the BIOS, and F8 is popup boot.
On my backup computer, F2 enters the BIOS, and F10 is popup boot. There's
really no way of predicting what they'll use. But the choices should be
printed at the bottom of the first screen. Even my laptop with the UEFI
BIOS, has such choices, and I've booted USB flash devices there. But
the screen goes by so quickly, it's hard to press the appropriate F key
on that one. You press "Pause/Break" key, to make the screen stand still,
so you can actually read a "fast boot screen".
That's the most likely way you'll get to use USB flash boot devices.
It doesn't make as much sense, to offer a permanent boot option
that way. While there may actually be a means in the BIOS setup screen,
to set a USB device as the default boot device, you're more likely to be
unplugging it after the current session. So it's less important to
make that selection permanent. But at least if there is a "pop up boot"
option, you should have access to USB boot.
In terms of what USB ports support boot, it would be any USB ports
supported by the Southbridge chip. For example, if you had Southbridge
and also a separate NEC USB3 chip, the BIOS is most likely to boot
from a Southbridge port, and it's less likely they'll include boot
support on the USB3 port. That's the trend in the past - the separate
peripheral chips don't tend to get support from AMI. The manufacturer (NEC)
of the chip may write some support code for it, but it's just not
going to be as good as the support for the main chip (Southbridge).
The code written by AMI, ensures the CPU, Northbridge and Southbridge,
support the full feature set. Any add-on chips aren't handled by the main
code. Once you get in Windows, proper Windows drivers ensure all the
USB ports work (and then the nightmare ends).