Apple in August refreshed the 2020 iMac lineup with a new 27-inch model that’s equipped with 10th-generation Intel processors, more RAM, more SSD settings, and faster AMD GPUs.
Unfortunately, some new Mac owners have been running into problems with their machines and have been reporting ongoing glitching with the graphics. There’s a 57-page thread on the MacRumors forums filled with complaints dating back to August, suggesting this is a problem that’s been impacting iMac owners since the new Macs came out.
Based on a poll, a good number of iMac owners who have the higher-end 5700XT GPU are seeing a white horizontal line flicker across the display on occasion, but the problem does not seem to impact all users.
Read more at MacRumors.com