Well you have to be careful with what you&#x27;re comparing. It would be rather unfair to compare the original UNIX design with a modern design like NT. UNIX did not have async I&#x2F;O. It even blocked syscalls in its original design. I think Linux added async I&#x2F;O quite recently (2.6?). I&#x27;m not really a kernel dev, but I have had to work on systems level stuff quite often on both OSs and from what I&#x27;ve seen NT has a much more richer I&#x2F;O model. The I&#x2F;O class&#x2F;device&#x2F;filter&#x2F;driver model of NT makes writing driver code less of a chore IMHO. Also async I&#x2F;O is supported on almost all I&#x2F;O devices. I believe its only network and disk on Linux.