iMac 27 inch 2020 - Screen Glitch (Random Lines Appear on Screen)

I just have Diablo III. Played it for an hour with full res + highest graphic options enabled. Now issues or anything. Yet I just started the iMac and the flickering appeared again.

I cannot refer to your glitches :/

Overall, that is good news for you at least. The thin line glitch is a small annoying thing - the full-scale system crash is an entirely different matter and if you don't suffer from that I would be happy and hopefully the flickering is fixed by a software update.

Just as a reference point, there was a not totally dissimilar issue with the higher-end graphics option (of two) with the mid-2011, 27-inch iMac (iMac 12,2). The AMD Radeon HD 6970M with either 1 Gbyte or 2 Gbyte of memory developed on-screen lines, tearing, and (iirc) sometimes simply freezing. Many owners, myself included, had to haul their machines to Apple Stores or certified repair techs and wait for the swap to be made under AppleCare.

Two years after the machines were released, Apple finally instituted a free graphics card replacement policy up to three years after the machine was purchased.

Oh wow! Thanks for sharing. That model was sold between May 2011 and Oct 2012. And it was only in August 2013 when they finally opened a replacement programme for the issue. I wonder if initially that too was suspected to be a SW issue only, or straight clearly classified as a HW problem.

Hmmm, either way, I'm one step closer to asking for a downgrade to 5700 replacement instead of the glitchy XT.

To clarify, in case I made things perfectly obscure: Apple was replacing 2011 iMacs with the issue well before August, 2013 under AppleCare (and, iirc, after the first 90 days after pour case, out of the "goodness" of their hearts). It was only in August, 2013 that that service notice leaked (or was purposely leaked; trying to read Apple is often like trying to read the pre-1989 Kremlin). I wish I could remember the month and year when mine got replaced, but I can't. I have a vague idea that the issue didn't develop for me on day one (early November, 2011), but waited until the following spring sometime to rear its ugly whatever — possibly thermal?

A little more Intertubes searching turned up tales of being able to cure (literally) the 2011 model issue. But the 2020 model issue appears from the git-go in some people's machines, so please don't take your still-under-warranty machines apart just yet.

From my experience dealing with Apple over ~ 30 years, they do see statistics on reasons for AppleCare calls, and they will deal with this, but it's unrealistic to expect an engineering change in a few weeks. (They have to reproduce the issue in machines coming off the assembly line, do a bunch more of that to get an idea of the prevalence, troubleshoot to discover the root cause, and then implement a solution, which could turn out to be hardware or software). Seems like most people here realize that, and are either bringing recently purchased machines back during return periods, or holding off ordering this CTO option until a fix has been devised, both of which make perfect sense.

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I have opted to go for 5700 and the 8 core instead of 10 core and 5700XT graphics it’s not like it’s going to be terrible or anything, I just cannot wait around for Apple to fix the issue with the line glitches as well as loud fans. I mean my late 2012, 27in core i7 with 1gb of graphics still works fine today, so this new one will radically out do it regardless.

Time is my main concern here as well. I do not doubt Apple will resolve this sooner or later. I just don’t have time to wait around, checking forums, installing betas. The actual return, replacement and setup also take time and effort. Just too much hassle.

@DanH35 off topic question, are you saying i7 is quieter than the i9? Can you link me up with some reference where this is demonstrated please?

Some people have expressed that they can hear the fans even idling for the 10 core, not sure how bad it is but I hazard a guess in a silent room it could get annoying. This guy on YouTube below goes through the screen glitch and mentions the fan noise. I think it depends on the person, as for me I am used to a silent iMac, only hearing fans when rendering.

https://www.youtube.com/watch?v=hKnnako5FUg

Max Tech compares the 8 core vs the 10 core and convinced me to go for the former...

https://www.youtube.com/watch?v=4Fa5yNwsK7o

I just want to let everyone know that I have not seen any lines since I first configured my iMac and they were not as severe as the photos I have seen, they were very brief and very thin. Also I do hear the fan when doing non-intensive tasks but it is very quiet. I don't think this should put anyone off of purchasing. Just exchange it if it has crashing/lines or any other issue.

I'm just wondering is it the 10 core i9 cpu that's causing the fan noise during idling or the 5700XT graphics causing it, or both? I'm assuming the 8 core i7 cpu with 5700 graphics will provide a quiet experience while emailing and web browsing (just like it does for me on my MacBook Pro Retina 13" Early 2015). I work in a quiet office environment, so definitely prefer not to hear the fans for non-intensive tasks.

@DanH35 Can you please confirm your experience, fan noise, no graphical glitches, etc, when you get your 8 core 5700 iMac?

I’m not aaron but I too can hear the fan running while idle. It’s not loud by any stretch but is audible. I would say same noise level as my external WD Black drive. Just humming.

Got the 10 core i9 with the glitchy 5700XT

Does anyone have any measurements, or links to videos with data on the actual fan speeds at more or less idle?

For comparison, my 2017 27-inch 5K with a quad-core i7 runs about 45 - 48 C and 1200 - 2300 rpm fan speed. I tend not to be able to hear the fan at those speeds because (1) at this time of year, I have a circulation fan and an air purifier running, and (2) at my age, my high-end hearing is shot.

So do you think it's the 10-core i9 cpu or the 5700XT causing the fans to kick in while idle, or perhaps both?

I'm also wondering if the glitchy issue associated with the 5700XT is causing the fans to ramp up more than it should!?

To be honest, I don't understand why Apple doesn't release documentation under their iMac specs page on fan noise (db) at idle vs web browsing vs say intensive workflows in Final Cut Pro video editing, wattage under certain loads, benchmark scores for cpu and graphics, and frame rates under certain games, etc. It seems to me that these are key stats they have no-doubt documented for themselves during their design process and internal testing, that we as customers are also mostly interested in before purchasing an iMac. Instead, we're left to gather such information from alternative sources such as tech YouTube channels and membership forums such as this one, which is subject to interpretation and personal experience.

Despite your qualifiers ("subject to interpretation and personal experience"), you answered your own question, I believe. Why should Apple do those things (and pay good money for engineers and test facilities) when others will do it for them?

Maybe more to the point, benchmark scores are just that — not real life experience with real life workflows. And sound level, however accurately it can be measured under test circumstances, will differ according to user (insensitive to low-level, high frequency sounds vs. hypersensitive and everything in between) and environment (sound absorbing surfaces vs, sound reflecting ones; quiet, one-person offices or studios vs. noisy, open-plan offices and natural sound environment vs. plugged into Air Pods all the time). Benchmarks are better for comparing two sets of hardware than for guaranteeing a single experience.