[SOLVED] [SOLVED] No POST with GPU installed (Z390 Designare, Radeon RX 580)

May 29, 2020
4
1
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SOLUTION: Change the microswitch on the GPU card from gaming mode to compute mode

Hi everyone

I've just built a new machine using this spec:

https://uk.pcpartpicker.com/list/YB3QvW

The system was working using the integrated GPU, but I decided to install a dedicated GPU so bought a Sapphire Radeon RX 580 8 GB PULSE. The problem is that the machine will not POST with the Sapphire in a PCIe slot. If I remove it then the machine will POST again. I get a solid red VGA LED on the motherboard. I have tried resetting the CMOS, specifically setting the BIOS to use the PCIe interface as the default output (rather than on auto), and disabling the iGPU. The power cable is connected to the GPU.

Any advice would be greatly appreciated.

Thanks in advance
 
Last edited:
Solution
Guys I sorted it, hopefully this will help any other with this issue. The GPU has a tiny microswitch which changes it between "gaming mode" and "compute mode". The default is gaming mode. When I changed it to compute mode, the system completed POST and booted. Weirdly I don't get any picture on the screen until the OS has booted so presumably can't change BIOS settings. Also the red VGA LED is still lit on the motherboard so the board seems confused. But I am now typing this from macOS using hardware acceleration on the GPU, so I'm happy!
May 29, 2020
4
1
15
sorry I didn't see the first line of your reply. Yeah the monitor is connected to the RX, I have tried on both displayport and HDMI. But the VGA LED on the motherboard is not normal and indicates a problem with the GPU, but I have no idea how to diagnose what the problem actually is
 
May 29, 2020
4
1
15
Guys I sorted it, hopefully this will help any other with this issue. The GPU has a tiny microswitch which changes it between "gaming mode" and "compute mode". The default is gaming mode. When I changed it to compute mode, the system completed POST and booted. Weirdly I don't get any picture on the screen until the OS has booted so presumably can't change BIOS settings. Also the red VGA LED is still lit on the motherboard so the board seems confused. But I am now typing this from macOS using hardware acceleration on the GPU, so I'm happy!
 
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Solution