I recently bought a 2nd-hand iMac which has the following specifications:
- iMac (27-inch, Mid 2011)
- Processor: 3.4 GHz Intel Core i7
- Memory: 16 GB 1067 MHz DDR3
- Graphics: AMD Radeon HD 6970M 2048 MB
- Storage: 1TB SATA HD
It had Sierra installed, and I used it for a couple of weeks.
I then upgraded to High Sierra and noticed that it is very slow.
It seems to lag everywhere, even when inputting text into this text field in Safari. The lag is not extreme, but it is there.
I assume this 2011 iMac has insufficient processing power to smoothly run High Sierra which was released in 2017, so I would like to downgrade to an earlier OS.
I considered downgrading to Sierra, but I wonder whether it would be even better to downgrade to an earlier OS such as El Capitan or earlier.
From the MacOS release dates on the Wikipedia page, I assume this iMac was released with Lion.
I use XCode 9 and not much else, and I assume this iMac has a 64-bit processor, and I don't know which was the first OS to support 64-bit.
I'd like to downgrade to the earliest version that I can, to ensure the smoothest experience.
So which OS should I downgrade to?