Requirements difference between Yosemite and Sierra I have a late-2009 iMac which seems to have held up pretty well, especially since upgrading the RAM to 12GB.

I only fairly recently updated the OS to Yosemite after running Lion for so many years.

The OS update my have made my Mac a little slower, but if so then not by a great deal. But I could probably do with updating again — to Sierra — as certain programs require a more recent OS than what I have.

I am a bit concerned that running Sierra will put too much of a strain on my machine... or are the requirements not a whole lot different to any other versions of OS X over the last 5 years or so?
Here are the general requirements as specified by Apple:
OS X Yosemite

OS X Yosemite - Technical Specifications
General Requirements OS X
v10.6.8 or later
2GB of memory
8GB of available storage
Some features require an Apple ID; terms apply.
Some features require a compatible
Internet service provider; fees may apply.

macOS Sierra

MacOS Sierra - Technical Specifications
General Requirements
OS X 10.7.5 or later
2GB of memory
8.8GB of available storage
Some features require an Apple ID; terms apply.
Some features require a compatible Internet service provider; fees may apply.