Z77 Extreme 4 error D6 with iGPU/half ram gone

Hi
I'm writing to you as last resort because I'm out of options (can't fill the form on asrock support, the site ask for model but don't accpet any entries).

So, I've a Z77 Extreme 4 motherboard with an I7-3770 intel processor and 16Gb of ram (4x4Gb). Bios is version 2.90. I don't use a discrete graphic card, I use only the integrated iGPU (hd4000) of the processor.
All was working fine for years and last week, without notice or any change in hardware / software, at boot, the screens went black with the code D6 on the mainboard. Clearing CMOS, removing ram, changing ram slots, disconnecting peripherals did nothing.

Then, I've installed a graphic card in the pci-e slot and the pc booted. After looking at the bios, I saw that the "onboard" igpu option was not present in the list anymore, I have only pci express and pci options now. Another shocking fact is that I loose half of the memory: 8Gb showed instead of 16Gb, despite the fact that all dimms were present in the 4 slots.
I've then tested the CPU and all dimms in another motherboard and they worked fine, even the iGPU of the processor, so I now 100% sure that the motherboard have a problem.

After googling this issue, I've seen numerous other users having the same problem (error D6) some say it may be related the bios chip, although I've tried multiple times to reflash the bios with differents versions, without success (the bios flashed successfully each time, but the issue was not resolved), some says it may be the socket pins (I've looked closely and not found any bend pin) or even ram slot...

So I ask you if anyone have suggestions or advices regarding this issue. This is a big deal for me because otherwise I must change the whole computer base (motherboard + cpu + ram) which is rather costly as you can imagine.

Thanks you very much

Elclaudio wrote: So, I've a Z77 Extreme 4 motherboard with an I7-3770 intel processor and 16Gb Out of date equipment If you are able to get it going again something else will fail soon. which is rather costly as you can imagine. With any kind of luck the new up to date build will last as long as the Z77 build. Thanks you very much