[Resolved] FullScreen for 3840x2160, guest Win10

[doug fromox]

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ModEdit; Posts split from: FullScreen for 1920x1080 resolution, Host /Guest macOS Sierra

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Been using VBox for 2 years, love it.
Just recently upgraded to 5.2.6 because the Windows 10 Update was complaining about drivers and not completing - 5.2.6 fixed that problem.

But then the screen resolution was bad (I have a fancy Dell 4K UHD monitor, but the highest packaged res after the upgrade to 5.2.6 & whatever the Windows 10 Upgrade did is 1400x1050).

However, that was fixed after applying the fix on this thread. In my case it was (with VM off)...
VBoxManage setextradata "Windows 10" "VBoxInternal2/EfiGraphicsResolution" "3840x2160"

After booting Windows 10 in VBox and logging in, there was a flicker and then it changed to full screen in UHD.

So thanks to all on this thread for the help.
Doug.
PS. The "Shared Folder" to my OSX file system didn't automatically re-establish either, until I clicked on VBox > Settings > Shared Folders and then simply clicked on the mapping shown and then without editing anything click OK - that seemed to nudge things correctly so now I can see my OSX files.

[socratis]

@doug fromox
Sure, the EFI settings could apply to any guest that's using EFI. The only question is why are you using EFI for a Win10 host, which 1) doesn't need it, and 2) it's not the default.

[doug fromox]

Sorry, can't answer your questions, all I know is that before I ran the EFI command the resolution maxed out at 1400x1050 (and was the wrong aspect ratio, there were unused strips of screen down either side), and that after I ran the command I got full 3840x2160 res back again (at the correct ratio).
I'll leave it to the experts to figure out why it worked...

[socratis]

I know why it worked. Because you told it to.
That was not the question, but never mind...

[doug fromox]

Hi again Socratis.
Last time we conversed I was smugly confident that I'd solved my resolution problem, but was intrigued by your final riddle "I know why it worked. Because you told it to. That was not the question, but never mind...".

Now, after further upgrading VirtualBox (to 5.2.18) and my guest Windows10 (to 1803, along with the corresponding Guest Additions) running on a MacBook under 10.14 (Mojave), I found that the steps that I outlined above (ie. ' VBoxManage setextradata "Windows 10" "VBoxInternal2/EfiGraphicsResolution" "3840x2160" ') did not restore full-screen on my 3840x2160 display. That is, the height is fully extended but there is nearly 3 inches of unused screen on both sides (or about 78 sq in !!! ). I've repeated the installation of the Guest Additions and rerun the 'setextradata' command several times, to no avail.

So now, with your riddle in mind, I'm thinking that I must have earlier tried some other fix besides the one noted above, and it was that which gave me the extra 78 sq in of screen. But I don't remember what else I did.

So I'm wondering if you can give me some extra hints?
Ta, Doug

[socratis]

Did you try to change the resolution from within the guest? The EfiGraphicsResolution trick really applies to the boot screen, after that the guest can set its own resolution independently. As it should be able to do...

[doug fromox]

Bizarrely, the Windows10 guest is now using all the screen, and I did nothing extra, ie. did not do as you suggested. At the risk of boring you, here is the sequence of events in case they provide some clues that help others in future...

After posting my call for help yesterday, I left the Windows10 guest running in VirtualBox and unplugged my Dell external screen (because occasionally it causes my Mac to freeze when it starts to come out of sleep mode, requiring a reboot) and put the Mac into sleep mode overnight. Then about 24 hours later I "woke" my Mac (to see if you'd responded to my post) and plugged the Dell screen back in (expecting to see Windows10 still in its restricted space). The Dell initially showed a lot of horizontal "snow" (still spots and lines, not moving). So I moved the mouse from my Mac screen into the Dell screen and "clicked". The snow cleared in a blink and, hey presto, the Windows10 was now full screen. I have shutdown the Windows10 guest and then shutdown VirtualBox, and when I restarted them both from scratch Windows10 was again in full-screen, so the change appears to be permanent.

Thanks for your help, I'll keep it up my sleeve in case I run into trouble next time...
Cheers, Doug.

[socratis]

Glad you got it going. I'll mark it as [Resolved], but not before splitting your posts from the original thread "FullScreen for 1920x1080 resolution, Host /Guest macOS Sierra", because your guest is simply not OSX Sierra. And I'm going to move it to the "Windows Guests" at the same time, where it actually belongs.