Black screen on UEFI

The Dr Debug/POST code (MB code) of A6 (or other A0 - A6 code) is normally displayed when the board is in the UEFI user interface. The last part of POST checks the SATA drives, so one of those codes remains displayed until the POST process is complete, or really until the OS boot process has started.

Usually the POST/MB codes are displayed when the POST process fails at one particular stage or step, which means an error occurred during that step, whose code is then displayed to tell us what step failed. Since the A0 - A6 codes for the testing of the SATA drives is at the end of the all the POST tests, seeing one of those codes does not necessarily mean an error occurred.

When the PC starts, do you have a POST beep speaker connected to the board? If so, do you hear the single short beep which means POST completed successfully? Are all your SATA drives working when the PC boots?

The display of the A6 code makes me think your board is really in the UEFI user interface mode, or trying to be, but you aren't seeing it displayed for some reason.

What video source are you using, a video card or the Intel integrated graphics?

Are you using more than one monitor at the same time with that PC? The video source may select one video output as the main output when the UEFI UI is being displayed, which may not be the same video output when Windows is running.

Are you using a TV as a monitor?

How is the monitor connected to the video source? With a cable directly between the monitor and source, or are you using an adapter of some kind?

Do you have more than one cable connected to the video source, but the cable(s) are not connected to a monitor? Or do you have, for example, two cables connected to the video source, and both connected to the monitor?

Your advanced monitor is most likely the problem. Or at least that is easy to test.

You can run the monitor with only one cable connected, right? Displayport usually has precedence over HDMI, so disconnect the HDMI cable first.

Then again, you no doubt know more about your monitor than I do, so try whichever single cable you think will work.

Please let us know if this makes a difference, and "fixes" your issue. I know it is really a work around, but the basic knowledge that your monitor and video input configuration will not allow the UEFI UI to be displayed is important for us to know if others have this problem.

It might also cause ASRock to look into this and see if they can do anything about it. The UEFI is displayed at 1080P by default, and can only be set to a lower resolution.

Great, but if that did not work I would not know what to do next.

Most things are obvious after we learn what is happening. I'm still not sure exactly what is happening in your case.

When I use a dual monitor configuration, one on Displayport, the other on HDMI, only one monitor is active when in the UEFI UI. The same is true when I use one on Displayport, and the other on DVI-D. In both cases only the monitor on Displayport is active when in the UEFI UI. This is using an Nvidia chip video card in both cases, two slightly different cards. Once Windows boots, both monitors are working. Not the same configuration as yours at all, only the use of two outputs at the same time.

Questions for you, when you use just the Displayport connection, what does the resolution and refresh rate become? Just trying to correlate what the cause might be.

The Gsync factor is another thing I wonder about, but your issue is the first we've had like this. I know those monitors are in use so I doubt that is the problem alone.

I'm having a similar issue but changing cords hasn't worked.