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

There’s a lot of happy customers of the 5700 model, and I can perfectly understand and respect their decision to buy it. I was also really tempted to order the 5700 model instead of the problematic 5700XT, but for me... I concluded why should I give Apple my money in exchange for a less powerful graphics card than the one I really want, while they continue to ignore their customers with the 5700XT issue.

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.

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.

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'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.

Apple does publish some acoustic benchmarks, for idle at least you can find the measured dB values at the bottom of each product spec:

https://support.apple.com/kb/SP821

https://support.apple.com/kb/SP790

I think I've seen somewhere on their website also a comparison of acoustic performance for peak CPU usage, but can't find it now.

Either way, by the raw numbers the iMac 2020 is supposed to be quieter than the iMac 2019, but my experience is the very opposite. The 2019 model I had was dead quiet when idle or when browsing in Safari. Whereas the 2020 model just hums here audibly while I'm writing this in Safari and have 4 more tabs open and nothing else running. Same low temperature, same RPM and same low CPU usage.

I've no scientific proof for this, but my theory is that the 2020 iMac is perceived as louder perhaps because of the "different shape of the sound". From iMac 2020 they've removed the mechanical drive thus left a lot of empty space in its place: https://youtu.be/GIHSyamWnh4?t=63. I think this might be causing some sort of echoing of the fan noise. For me personally the 2020 iMac sounds more "tinny", or as some other commenter said, more "coarse". The actual dB values might be same or lower, but the sound itself is more annoying to my ears lol.

And because of that, I decided to keep my i9 actually. I don't think the i7 would be any quieter in regards of ambient idle noise. And as for the peak CPU fan noise — I don't really care if it peaks 43dB a second or two later or earlier, it's loud anyway and I'll take the 10% gain in compiling time if it's available.

I’m thinking of returning for the i7 and standard glass to save the money since if it’s not quiet I would want the Apple Silicon version anyway. Maybe I should make a video on this. Might get some views lol.