Apple Silicon iMacs referenced in newest macOS Big Sur 11.3 beta

Within the macOS Big Sur 11.3 beta 5, released yesterday to developers and public beta users, references to new iMac models in the operating system’s code have been identified by 9to5Mac, further bolstering reports that Apple is working on new iMacs with Apple Silicon chips.

Artist's conception render of an Apple silicon-powered iMac (2021) (image:
Artist’s conception render of an Apple silicon-powered iMac (2021) (image:

Filipe Espósito for 9to5Mac:

The latest beta version of macOS Big Sur comes with codes for two new iMacs, which are identified as “iMac21,1” and “iMac21,2” …Earlier this year, Bloomberg reported that the codenames of the new iMacs with Apple Silicon chips are J456 and J457, and 9to5Mac was able to confirm that the new models listed in the latest macOS Big Sur beta have the same codename.

Last week, a developer noticed some crash reports in their app coming from an unknown iMac powered by an ARM processor. At the same time, Apple recently discontinued the iMac Pro and some configurations of the 21.5-inch iMac, which suggests that the updated iMac with M1 (or another Apple Silicon chip) is indeed coming soon.

MacDailyNews Take: Tuesday, March 30th via press release?


  1. I just have this fear a new stock 27″ or larger Apple Silicon iMac will be on par speed-wise with my 2019 16 core Mac Pro for a lot less money. Adding insult to an already injurious Mac Pro history.

  2. My 2009 iMac has bit the dust – but I’m waiting for these – in the meanwhile, got a used 2017 iMac to hold me over. Loosing the ‘chin’ should make the 21.5″ size more than adequate for me, plus my desk won’t handle the 27.

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