Question Asus Prime B310M-K R2.0

[masteramp]

Hi, I am not an newbie, I have build some computers for my friends, but I didn't see this specific problem like with this board. Also the configuration:
- Asus H310M-K R2.0
- Core i5 8400
- 2x 8GB GSkill Aegis DDR4 3000
- Radeon Vega 64 / RX580 / RX470 / HD5770
- Gigabyte P750GM / EVGA 650 BQ

If is in the PCIE Slot inserted the graphic card without external supply connector, runs as primary without problem. If I connect any graphic card with the external supply needs including old HD5770, the graphics output goes from internal graphics. The PCIE Graphic card normally heats, lights and the vents are turns, but probably is not recognized right from MOBO.
If I set the default graphic adapter in Bios to PCIE, the next boot is in the "safe mode" and the display adapter in BIOS is setted back to CPU! Then I have flashed the MOBO Bios to latest available from ASUS pages but didn't help, the behavior is the same. I have checked it with two PSUs, from that the EVGA is unused and brand new.
What can I try to run my setup with the more gaming graphic card instead of integrated or office graphic card? Some PCIE setup or something in the consumption setup?

 

[boju]

Pcie power connected to card means no display but running without external power = igpu as primary display? Only if vga cable was connected to mainboard instead.

 

[masteramp]

Pcie power connected to card means no display but running without external power = igpu as primary display? Only if vga cable was connected to mainboard instead.

No, with this mainboard can I run only the graphic cards without need of additional power supply and the display output goes primary from this PCIE graphic card. If i try to run the graphic card with PCIE PSU connector/s and of course the connector / s are connected to proper cable/s from PSU (Gigabyte 750W / EVGA 650W), the graphic card is not right recognized and the display goes from integrated graphics and not from the additional PCIE card. PSUs are OK and I can measure the 12V at the output connectors. The graphic cards itself goes in the other motherboards without problems.

 

[boju]

Show us a picture of the back of your computer.

 

[masteramp]

Show us a picture of the back of your computer.

I i can take the photo until I will be at home in one pair of hours. I use the case AeroCool Atomic Lite: https://aerocool.io/product/atomic-lite/
But how can you help the photo of the back of my computer? You mean, that the graphic card is not proper installed in slot? Also I have wroten, that with the "office" graphic card without need of external 12V supply run the computer from this PCIE card as primary. The problem is only with the more powerfull graphic cards. I think, it should be not an mechanical / electrical problem due to poorly installed graphic card...