iMac Glitches

[BurnyC]

Hi guys,

I've got a late 2015 27" iMac (specs below)

Recently I've been seeing a 'glitch' kind of effect on the startup screen, which I got a quick video of (below). Also, does anyone else think it boots quite slowly? It's got the 1TB Fusion Drive with 911mb free. I may be spoilt by the new Mac Pro at work however, but I also think it's a bit slower than my 2009 MacBook Pro that I recently stuck a SSD in to give it a new lease of life. I think I've managed to speed up the process by stripping back the programs that load on startup. I also saw something about USB peripherals messing with it, and currently only my Wacom Bamboo graphics tablet is plugged in, so I've disconnected that.



Also, during a re-boot it completely freaked out and I got this weird 'shutter' effect. I only managed to catch the end of it and couldn't reproduce it, but it started from the bottom and went up to the top, revealing the contents of the screen as it went, like a weird PowerPoint effect!



Besides these issues, I never have any screen or performance issues, and use it for graphic design and video editing/animation, but I'm just a little worried about any impending problem whilst it's still in warranty! Also, seeing as it was so expensive and my first new computer since 2009, I'd like it to be perfect. Just to add, I've also run Apple Diagnostics and it couldn't find anything.

Thanks in advance for any advice/words of wisdom!

 

[Paprika123]

I'd start with a PRAM and SMC reset and see if that makes a difference although I doubt it will.

Failing that get it into Apple as there's stuff in the logs that can indicate more that the diagnostics doesn't show up, it wouldn't be the first time I've seen one of these with faulty graphics.

 

[BurnyC]

I'd start with a PRAM and SMC reset and see if that makes a difference although I doubt it will.

Failing that get it into Apple as there's stuff in the logs that can indicate more that the diagnostics doesn't show up, it wouldn't be the first time I've seen one of these with faulty graphics.

Thanks for your suggestions! Stupidly I didn't think of doing a PRAM or SMC reset, despite doing them numerous times trying to sort out my MacBook when I fitted the new battery! So far, after two test boots, it hasn't displayed any glitching, and theres less hang in the progress of the loading bar. Seeing as the glitch was consistent with every startup I have some hope! Might be a wake-up call to get the extended Apple Care whilst I can...