 However, during this time the speed of computers grew greatly in relation to networking systems, and the disadvantages in performance came to overwhelm the advantages in development terms.Many attempts were made to adapt the existing systems to have better performance, but the overhead was always considerable and most of these efforts required the user-space programs to be moved back into the kernel.By 2000, most large-scale (Mach-like) efforts had ended, although Apple's macOS, released in 2001, uses a hybrid kernel called XNU, which combines a heavily modified (hybrid) OSFMK 7.3 kernel with code from BSD UNIX, and this kernel is also used in iOS, tvOS, and watchOS.