For those determined to revive a legacy Mac, the community generally agrees on one method: you must find a machine that still has the "Purchases" tab active in the Mac App Store (though this is becoming increasingly unreliable as Apple revokes older certificates). Alternatively, trusted community archives (like the Internet Archive’s software library) often house "unmodified" checksums.
To recap:
: Introduced App Nap , which slows down applications not currently in use to save battery, and Timer Coalescing , which groups background tasks to reduce CPU wake-ups.
This creates a 7GB sparse image.
Before downloading or creating an image, you must understand the difference between the two primary formats.