Safari Tab overview Graphics issue iMac Late 2015

Try setting up another admin user account to see if the same problem continues. If Back-to-My Mac is selected in System Preferences, the Guest account will not work. The intent is to see if it is specific to one account or a system wide problem. This account can be deleted later. Please post if this worked or not.

Isolating an issue by using another user account

If the problem is still there, try booting into the Safe Mode using your normal account. Disconnect all peripherals except those needed for the test. Shut down the computer and then power it back up after waiting 10 seconds. Immediately after hearing the startup chime, hold down the shift key and continue to hold it until the gray Apple icon and a progress bar appear. The boot up is significantly slower than normal. This will reset some caches, forces a directory check, and disables all startup and login items, among other things. When you reboot normally, the initial reboot may be slower than normal. If the system operates normally, there may be 3rd party applications which are causing a problem. Try deleting/disabling the third party applications after a restart by using the application un-installer or by using the developer’s uninstall instructions. For each disable/delete, you will need to restart if you don't do them all at once. Please post if this worked or not.

Safe Mode - About

Safe Mode Startup – El Capitan. also Sierra

If it works in the Safe Mode, try running this program when booted normally and then copy and paste the output in a reply. The program was created by Etresoft, a frequent contributor. Please use copy and paste as screen shots can be hard to read. Click “Share Report” button in the toolbar, select “Copy to Clipboard” and then paste into a reply. This will show what is running on your computer. No personal information is shown. You can run the report for free at least once, but if you run it several times, at some point it will ask you to pay a license fee.

Etrecheck – System Information

I tried booting in safe mode and Safari worked fine in that mode, although graphics were much slower. Since booting back into normal mode the problem seems to have gone away. Maybe safe mode cleaned something up, it did take a very long time for macOS to come up. I can now no longer reproduce the problem, previously the problem would occur very regularly.

Still no luck, emptying caches doesn't help.

I did find a way of getting the display to behave once it starts flashing. Go to Preferences->Displays and select scaled. Change the scale and then set it back to default. The display will go back to normal and the VT-d errors will stop. At least now I can continue to use the machine without rebooting. It really looks like the driver is misbehaving.

I have encountered the same issue. I also have an iMac late 2015 and the problem has only arisen since updating to Mojave. When I click the "tab overview" button in Safari it sends the display haywire, just as described in the original post.

I've just tried the safe mode boot. I couldn't replicate the issue in safe mode. So I've rebooted again and so far no recurrence of the issue. Hopefully that has sorted it out.

Did you try using it in another admin user account or the Safe Mode? Does it happen if you use another browser?

I have found another way to, as it were, resolve the problem. As it only happens when the tab overview button is clicked, just remove that button from the Safari toolbar to stop yourself using it. The only thing I ever used it for was to get to the iCloud Tabs, but it turns out there is another button you can add to the toolbar just for that which doesn't exhibit the same problem.

It's a sort of fix.

This also fixed my issue. I chatted with tech support and was told if it worked ok in safe mode I needed to reinstall OS. Safe mode worked fine then rebooted into normal and it has been working right ever since.

Tim

Try going to Safari/Preferences/Advanced and enable the Develop menu in the menu bar. Then go there and select Empty Caches to see if that helps.

That was short lived. The problem occurred again today, the same VT-d fault was continually logged to the console when it happened:

vtd[0] fault: device 1:0:0 reason 0x6 R:0xf77c0000

The problem occurs far less frequently once going into safe mode but it doesn't seem to have solved it.

If you disconnect the external monitor and restart the computer, does it work normally?

Good.

The Safe Mode will reset some caches, forces a directory check, and disables all startup and login items, among other things.

Yes, it still occurs even without the external monitor, but even worse. The horizontal resolution seems to drop in half on the built-in display. It'll go back to the normal resolution when I reconnect the external monitor, but the flickering continues.

Just installed macOS 10.14.1 that includes Safari 12.0.1, let's see if that helps.

No difference, just got the graphics failure with the latest updates. Trying the Empty Caches now.

This happens to me also - haven't tried to troubleshoot it yet but it's pretty bananas. Only happens on my 5k Ultrafine display - my internal display is fine afterwards but I have to reboot to get it to go away.

Haven't tried to isolate it on any other accounts yet but definitely happens over here. Hugely annoying - I don't use that button and accidentally trigger it with a pinch zoom out when it happens, so I had to set up a BetterTouchTool shortcut for Safari only that overrides the pinch zoom and does nothing instead.