bad sector wrote:

Come to think of it there having been very few times when I _could_
enter into BIOS for editing while holding down the 'Del' key, maybe
it wasn't because of the delete key at all but because of some other
hangup.

Since you are using a USB-only keyboard (and likely a USB-only mouse,
too), check the BIOS is *not* set to enable legacy devices (which are
PS/2 input devices).

Another setting in BIOS is how long to wait at the POST screen. In my
BIOS (UEFI), I go there under the Boot tab to configure the timeout for
the Setup Prompt Timetout. Some default to just 1 second which isn't
even enough time for you to notice it's time when you can hit the hotkey
to get into BIOS. I can't see what is my value unless I reboot, but my
guess is that I upped it to 4 (seconds).

The manual for your mobo is at:
https://dlcdnets.asus.com/pub/ASUS/m...ula_manual.zip

Page 3-7 has a screenshot of the main BIOS screen. There's a Boot tab,
so I looked under there. I did not find a timeout that I could set for
holding on the POST screen, but there is a "Quick Boot" setting (enabled
by default). I would disable that, because info in the POST screen is
often critical to debugging hardware problems, like seeing if the BIOS
found all the internal drives (CD/DVD, HDD, SSD).

I would also disable the Fullscreen Logo settings. That's there ad
banner to announce you bought an Asus product. Big whoopdee doo. Often
it obliterates some, or all, of the POST screen. It doesn't save any
time nor does it consume more. It's just a nuisance to experts merely
to hide the tech data from boobs.

There is a "Hit 'Del' Message Display" setting to show the prompt to hit
Del on the POST screen. Is that enabled?

Under the Advanced tab, USB config, I'd try setting Legacy USB Support
to Enabled (instead of the Auto default) just to see if the USB keyboard
behaves better during the POST (BIOS startup up to POST screen, but
before the OS loads). You'll also want to make sure the USB 2.0
controller is set to HiSpeed mode.