Asus p8z77-v lk - integrated vga not found (1275v2)

Hello, ppl

Here’s the situation:
recently i got my hands on asus mobo p8z77v-lk with i3-2100 - and it works ok with cpu’s internal video core. Now i have a xeon 1275v2, which has an internal gfx intel hd p4000, but i receive a “no vga detected” post beeps with this cpu. I suppose, bios does not support this video out of the box. Btw, there’s another mobo p8z77 ws - it does fully support this cpu (also listed in supported). Is it possible to fix my bios, i.e. this situation is a known thing, or is this some weird case? Any ideas?

p.s. p8z77v-lk works ok with 1275v2 if i provide pci-e discrete video card

I did a little digging (mmtool works ok for both mobo’s bioses):

p8z77 ws:
- csmcore
- csmvideo
- bbvideo

- IntelSaGopDriver
- IntelIvbGopDriver
- IntelSnbGopDriver
- csmcore
- csmvideo
- bbvideo

maybe i should switch csmcore+csmvideo from ws to v-lk?
or simply remove UEFI video drivers (Intel*GopDriver)?

I also checked cpu microcodes, both mobos support CPUID 306A9 (1275v2)
703 - first bios from ws-mobo, that officially supports 1275v2, has even older microcode, than in v-lk mobo’ 1402 bios.
but microcodes are not relevant to the internal graphics support, right?

upd: i did write a question to asus tech support (what was i thinking?)
and they replied to me with obvious statement, that ws-mobo does support 1275v2, and v-lk does not

i still think this is soft-only problem, and it can be resolved by bios mod
what should i start with? plz help, ideas needed