Disabling CSM with Dual Monitors - Default Display?

[ainsleyclark]

Hi all,

My new Sapphire RX580 came today and its working perfectly with High Sierra apart from one little bug bear.
I have two monitors attached, one HDMI cable to a Samsung HD Screen, and one Active DisplayPort to VGA adapter to an old VGA Samsung Screen.
The Problem:
If I have CSM enabled: It boots but there is a black screen on the VGA monitor Note: If I disconnect and reconnect the screen it works, but don't want to be doing that every time I boot.
If I have CSM disabled: It boots with everything working, but changes my default screen (when clover comes up) to the old VGA screen; would much prefer to have my big HD screen as the default screen when booting.

Tried swapping the ports around - no luck.

Thanks in advance.

 

[ainsleyclark]

Any ideas?

 

[ainsleyclark]

Anyone?

 

[neofusion]

Both monitors only work when CSM is disabled? Interesting, for me it's the reverse.

Anyway, primary monitor is typically decided by the video card. Here are two different threads on other websites with people discussing similar problems, albeit with Nvidia cards. In your case it's probably VGA > DVI > HDMI > DP or some variation on it.

It's possible you can get around the issue by some nifty use of adapters but in the end VGA is unsupported in Mac OS X; If there is any way you can get a newer secondary monitor instead, definitely go with that.