- Jul 31, 2012
- HD4600 / RX 570
- Mobile Phone
When Apple announced which Macs would still be supported by macOS 11, I found it hard to believe they dropped support for 2013 iMacs and kept support for the 2013 MBP and 2013 Mac Pro. There seemed to be no good reason to drop the Late 2013 iMac from their list of supported Macs. It's more than capable of running Big Sur, especially if a 2014 Mac mini is able to. It looks as if they use other criteria to determine which Macs can install and run the latest macOS.
After a good amount of research, it's clear to me now that Apple drew the line for Big Sur support at Desktop Macs and Macbook Pros that have Thunderbolt 2 controllers. The Mid 2014 15,1 iMac has TH2 ports, the 14,2 iMac doesn't. The Late 2013 iMac was announced, 9/24/13, just before TH2 was ready to be included in a Mac. The late 2013 MBP was released in the latter part of October that Fall and had TH2 ports. The first Mac to ever have them. That's why the Late 2013 MBPs get Big Sur support. The Mac Pro 6,1 of course, didn't ship until late December of 2013.
The Late 2013 27" iMacs have more than adequate GPU and CPU performance to run Big Sur, it's just that they were stuck with the older TH1 1st gen ports. The 2013 Mac Pro 6,1 has 6 TH2 ports so it made the cut for Big Sur.
The 2014 Mac mini has TH2 ports onboard and a low power dual core laptop CPU. It has a 5400 RPM HDD. Those are considered Big Sur capable. Can't imagine how painfully slow one would be with Big Sur installed. Would certainly require an SSD upgrade to be usable.
The following models are Thunderbolt 2 capable:
- MacBook (2015+)
- MacBook Pro (Late 2013+)
- Mac mini (2014+)
- iMac (2014+)
- iMac Pro (2017+)
- Mac Pro (2013+)
The main difference between Thunderbolt 1 and 2 is that version 2 has channel bonding and DisplayPort 1.2, for full 4K video support. Whereas Thunderbolt 1 has two independent 10 Gb/s channels, Thunderbolt 2 combines these to give one 20 Gb/s bidirectional channel. This leads to more efficient transfers, with less overhead, but the total bandwidth is unchanged. Apple seems to think that these differences are important enough to drop the TH1 based 2013 iMacs.