Supermicro X9SCV-Q: no boot options to define

Hello folks,

my apology for polluting this list with a non-FreeBSD specific problem,
but since Supermicro is a veryy often used vendor in the FreeBSD
user/developer community I might find help here much fast.

I got hands on onto an oldish Supermicro X9SCV-Q mainboard, equipted
with an older i5-25XXM CPU running at 2,5 GHz). The AMI BIOS has
version 2.10.1208 from 2012.
The board does initially a longer beep and the it sounds like two
or three very short beeps plus a last longer beep at a higher tune and
then the system ALWAYS jumps into the firmware/BIOS screen, no matter
whether I set a administrator password to protect the BIOS or not.
Apart from the suspect of damaged RAM (three beeps indicate RAM
problem above the first 64k block, two indicate PEI recovery or video
memory problems if I interpret the manual correctly).

Sometimes the POST screen shows some message like "... in Recovery
State", due to the off-phased HDMI attached monitor, I do not see the
first characters. Maybe someone knows what that might indicate.

I already have changed the memory banks and the memory seems to be
allright as the replacement memory has been checked thoroughly prior to
the test in another well running box and I also checked the memory on
another box with memtest tool without any suspicious indication.

The attempt to flash the latest firmware fails due to the fact that I
can not even define a boot device - either this process is cryptic or
it isn't documented and I'm too dull. A FreeDOS 1.1 prepared USB
flashdrive  isn't bootable as any other UEFI/non UEFI flashdrive: I can
see the USB drive as being attached to PCI bus in the firmware menu, I
also can define a symbolic name, but then I fail in defining the path
to the loader as suggested in the example (fs0:\file\loader.efi or so).
Any hint is welcome.

This board has been used successfully over the past years and was
equipted with a TPM module at connector 23 (TMP1 header) - I'm
unfamiliar with those technologies and my first guess apart from a
hardware failure was that the hardware could have been protected anyway
like it is done via secure boot. Unplugging that TPM header doesn'
change anything.

Also the boot of XigmaNAS latest USB flashed image or any FreeBSD (11,
12 CURRENT) latest USB flashed image failed so far.

Thanks for some help in adavnce,

oh