So much so in fact, Microsoft developed NT 3.1 first on non-x86 architectures (i860 and MIPS), then later ported to x86, to ensure no x86 specific code made it in.
NT supported quite a few architectures:
> https://en.wikipedia.org/wiki/Windows_NT#Supported_platforms
"Windows NT 3.1 was released for Intel x86 PC compatible and PC-98 platforms, and for DEC Alpha and ARC-compliant MIPS platforms. Windows NT 3.51 added support for the PowerPC processor in 1995"...
NT is a pretty interesting bit of PC history, I can highly recommend the book "Show Stopper!" by G. Pascal Zachary that recounts its development, and also dives a bit into why making the OS portable across CPU architectures was so important to the team at the time.
Well, it is true, but Windows did run BE on the original MIPS R3000 platform. And only on the R3K[0]. The CPU architecture flag is still defined on modern Windows as IMAGE_FILE_MACHINE_R3000BE. There's an early test build of Win3.1 + GDI somewhere that runs on this platform.
The actual first release of WinNT 3.1 only supported MIPS R4000 and higher, I think. In little endian mode.
[0] I know the Xbox used a modified NT kernel, I've seen claims that the Xbox 360 also was, which would make it the second NT system to run big endian. Not familiar enough with sources better than wikipedia to trust that it actually was.
I remember demoing the machines to astonished clients by running a stupid number of Clock apps on the desktop without a hitch.
Fun times.
Things were so weird and wonderful back then. You could get GCC from Microsoft for Windows NT 3.1 for Alpha (crazy). And when Windows NT 4.0 came out there was the FX32 subsystem that ran X86 apps on Alpha (very similar to Apple Rosetta but much earlier).
I did not realize Canada was such a hotbed of Windows NT RISC.
Nintendo GameCube and Wii are also PowerPC based. And somebody managed to have them run Windows NT: https://github.com/Wack0/entii-for-workcubes