Boot screen resolution with flashed graphics card

[cdf]

I have a flashed Maxwell card that displays a boot screen on my 4K display. While the resolution that I use in macOS is 1920 x 1080 (retina mode), the resolution of the boot screen seems fixed to the display's native, yet uncomfortable resolution of 3840 x 2160. I would like to have a boot screen at 1920 x 1080.

Since I had not read anything about such a limitation before getting the card, I thought that I would mention it here. I would also like to ask: is there anybody with a 4K-boot-screen-capable card that enjoys a comfortable boot screen resolution?

I have tried two things to change the resolution, but remain unsuccessful. My first strategy was to boot into the OS without the web driver (relying only on the EFI), and in the display preference pane, change the resolution to the desired one. Unfortunately, the setting doesn't carry over to the boot screen. My second approach was to add the NVRAM boot argument "Graphics Mode=1920x1080x32". Again, this did nothing.

 

[ActionableMango]

You can install rEFInd and set the resolution parameter to any valid resolution that your card and monitor support.

If you boot more than one OS, I recommend rEFInd anyway. It is by far my favorite method of selecting an OS. It is also significantly faster than holding down ALT/OPTION.

 

[cdf]

You can install rEFInd and set the resolution parameter to any valid resolution that your card and monitor support.

If you boot more than one OS, I recommend rEFInd anyway. It is by far my favorite method of selecting an OS. It is also significantly faster than holding down ALT/OPTION.

Thanks for the advice. I'll look into it if I can't figure this out otherwise.

 

[cdf]

Several months later, I've party solved this issue. This solution should be of interest to anyone with a graphics card capable of displaying a boot screen at 4K and, of course, a 4K display: Simply enter this in terminal

sudo nvram 4d1ede05-38c7-4a6a-9cc6-4bcca8b38c14:UIScale=%10

Here's the story: Although the rEFInd approach suggested by ActionableMango didn't work, it did reveal that the only supported resolution at boot is 3840 x 2160. So making things appear bigger must be a matter of enabling retina scaling for the boot screen. (Retina scaling works by using images that are twice as large as their non-retina counterparts.) Another clue came from a post on this forum for enabling a dark boot screen by setting a variable in NVRAM. Could there be a similar variable for enabling retina scaling for the boot screen? A list of Apple's NVRAM variables reveals a boot service variable called UIScale, and it turns out that setting this variable to 2 gives the desired result—well, sort of.

The setting enables a nice looking retina Apple logo during the first stage of the boot, instead of a small one. The logo matches the one that appears during the second stage, when macOS loads the graphics drivers and the 1920 x 1080 retina resolution set in System Preferences takes over. The appearance of the boot process of my cMP is now nearly just as appealing as that of my rMB. I've also verified that the setting makes the FileVault login use the retina resolution; it's really nice not to have to enter your password in a minuscule box!

Unfortunately, for some reason, the setting doesn't work for the recovery partition, which is what I really wanted it for. Perhaps another boot service variable is needed. I'll have to investigate. Of course, any ideas are welcomed!