With its debut in July 1993, Windows NT ushered in a gloriously pure 32-bit future, free of the 16-bit shackles of the past.
While the majority of PCs at the time were running MS-DOS, often with Microsoft's Windows 3.1 perched precariously atop, like a giant lemon balanced on a peanut, the kernel-based NT represented a stab at something entirely new.
Originally intended as a successor for IBM's OS/2, before the collaboration between the two companies foundered on the rocks of the success of Microsoft's Windows, NT required some tasty hardware.
Nothing less than a 386-class processor (for the Intel iteration) would do, and running it in less that 16MB would make for a very sub-par experience – astonishingly excessive for the time.
Development was famously led by DEC's Dave Cutler, who joined Microsoft five years earlier, with the goal of making the operating system portable via a common code base and a Hardware Abstraction Layer to do all the grungy low-level stuff.
Non-Intel architectures such as DEC's Alpha were initially supported but later dropped.