Sometimes my Mac Mini, plugged to an LG IPS screen, display some Glitches. For example, times ago, in my Launchpad appears these glitches:

enter image description here enter image description here enter image description here

To solve these glitches I had to restart the Mac. Now in my Safari's Top Sites there's this:

enter image description here (all these glitches were immortalised with screenshots).

However sometimes, when I wake my Mac from sleep, all the screen appear with a green tint, in that case, taking a screenshot, it appear without issues and, to solve the issue, is enough just put the Mac in sleep than wake it up again.

I can't understand the cause, Apple's Genius says that, for him, is the HDMI cable, my scare is that the trouble is the GPU because my AppleCare will expire soon... For you where is the problem? Are there some test to do?

  • Swapping the HDMI cable would be the first obvious test. – Tetsujin Feb 12 '16 at 10:07
  • If apple genius told you it's the HDMI cable, then why would you have any reason to think otherwise? Did you try a different cable? – Joonas Feb 12 '16 at 11:49
  • Genius accused the cable as his opinion just talking, he didn't see or try the Mac. Glitches are very rare so even changing the cable, glitch can appear after lot of times, in two months my AppleCare will expire and my scare is that, after that date, glitches will increase... – Matte.Car Feb 12 '16 at 11:53

If the Genius said that the problem is in the cable, you should try swapping the cable.

With that said, TEST YOUR GPU NOW. If there's indeed a problem, you really want to get it fixed now.

Run Apple Hardware Test (if you computer was released before June 2013) or Apple Diagnostics. Make sure that you run the relevant tests. Run some sort of GPU stress test like Unigine Heaven. If anything seems to be triggering errors, bring it to the Apple Store and try to get them to replace it. GPU replacement is expensive and you'd be much better off having Apple pay for it than you.

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