[AshamedCaptain]

Actually you might be surprised. Windows NT is _older_ than many of the "standards we take for granted in x86/PC land", and for example it does support multiple types of pre-ACPI ways of bringing up multiprocessor systems and specifically multiple types of interrupt controllers. Heck, x86 Windows even supports non-PC servers from Compaq and others; ever tried to press F5 during (old) Windows NT setup ?

As the OP said, all of this is abstracted by the Windows HAL, so it's just a matter of replacing the HAL (a separate binary). The problem is that the HAL is closed source. Outside of simple binary patches, I don't think anyone has come close to writing a new one.

[amarioguy]

Generally speaking part of the issue with a custom HAL nowadays is that Microsoft moved the HAL from being a DLL to being a statically linked library within the kernel (likely as a performance optimization and because there's no real need for a new HAL in most instances when HAL Extensions exist)

This merger of the kernel and HAL invariably means patching the HAL is now equivalent to patching the kernel

[monocasa]

ReactOS has written their own HALs.

[xattt]

> x86 Windows even supports non-PC servers from Compaq

Were there x86 but non-IBM compatible models or did you mean the alternate instruction sets (Alpha, PPC, RISC)?

[zinekeller]

Not GP. I'm not sure if there's a special Compaq version but there's a version (until Windows 2000, https://winworldpc.com/download/5204c39d-c3a9-5a68-11c3-a7c2...) for NEC PC-98 architecture which is x86-based but IBM PC-incompatible, so it's likely that a Compaq version exists.

[yuhong]

The Compaq is IBM PC compatible but uses a different HAL for SMP support. You can see all of them by looking at what NT4 shipped with for example.

[zinekeller]

Ah, Uniprocessor versus Multiprocessor HALs, I remember now!

[DeathArrow]

>Outside of simple binary patches, I don't think anyone has come close to writing a new one.

What about ReactOS, do they use a HAL implementation or not?