You may consider testing the motherboard out of the case with minimum configuration in a non-conductive surface.
Otherwise you may contact your local Intel® support team for warranty replacement.
I am really sorry for the inconvenience.
I have tried booting without the HDD attached (audio, USB and optical drive still attached) with the M/B still in the case. The boot splash only appears when the monitor is attached to the on-board video. I don't see a boot splash but I do get the boot audible when I insert any of the video cards into the PCIe x16 slot.
I'm certainly willing to try an out-of case minimal configuration. My thought was to leave the audio attached but remove all drives and USB connections. Does that make sense?
Any other suggestions or things I might try before initiating a warranty replacement?
Perhaps a firmware update for the graphics cards may help but should be done in a different system.
If the issue still persists, test the motherboard only with the processor and one memory stick, out of case, before sending it for replacement.
I did try running a minimal configuration (in the case) with only the audio header, memory and CPU attached. I could not get the video cards to be recognized in the PCIe slot with this configuration.
I'm unclear about what would be accomplished by trying the same thing with only a single memory stick? I'm also not certain that firmware updates on the video cards are warranted as they work in a much older generation M/B (Asus P5LP-LE) and also work in another M/B with an H77 chipset (see the following paragraph).
I installed an ASRock H77 Pro-M motherboard with all of the same hardware I had on the Intel DH77EB. The ASRock M/B recognized the video cards in its PCIe 16x slot without a problem. I was able to complete my build using the ASRock M/B.
It would seem that this would suggest the Intel board is defective. I am initiating the warranty return process.
Thanks for your suggestions.
I too have same problem. I have this Motherboard DH77EB . I am using with intel core i3-3220 cpu and 2x4gb 1600mhz ram. I recently purchased graphics card xfx r7 260x 2gb core edition online. This card has PCIe 16x 3.0. When I installed this card on motherboard, it never detected the card. Otherwise the same card is working on other latest as well as older motherboard. I also roll backed different MOBO BIOS but nothing worked for me.
And now few days back audio line out of MOBO starts dis-functioning.
Using a single memory stick is just a “best practice” recommendation. An update for the graphics card is recommended because not all the motherboards and BIOS are made the same even if they share the same chipset.
These are the only steps we can recommend without knowing if this is a compatibility issue or possibly two defective motherboards. Hopefully hdeetst will share his result after replacement.