Windows NT on Power Macintosh

On multiple occasions, a port that would have allowed running Windows NT on Power Macintosh systems was under consideration.
Initial efforts focused on porting the operating system to a generic system standard specification in the mid-1990s through support for the PowerPC Reference Platform (PReP) standard, later superseded by the Common Hardware Reference Platform (CHRP). Last-ditch licensing efforts to support Windows NT on Macintosh systems were proposed by Apple executives to Microsoft as late as mid-1997, even after the latter company dropped official support for the PowerPC CPU architecture in early 1997.
== History ==
Windows NT was ported to the PowerPC architecture by IBM during the year 1993. The first limited availability version based on Windows NT 3.5 was released in 1994 for a specific IBM RS/6000 model only.PA8600/PA-RISC. The lost history of PReP: Windows NT 3.5x and the RS/6000 40p, Virtually Fun. 2 August 2020. The first generally available release was Windows NT 3.51, which was commonly called "the PowerPC release" internally as a result. Windows NT is one of the few PowerPC-compatible operating systems of the era that ran in little-endian mode; Linux, Mac OS and AIX all run in big-endian mode.
The port was originally designed for systems based on the PowerPC Reference Platform, IBM's first attempt at defining a standard architecture for PowerPC systems. However, PReP was ultimately rejected by Apple during its transition to PowerPC processors, in part due to the specification aiming to leverage standard PC hardware. IBM therefore collaborated with Apple on the Common Hardware Reference Platform specification, which incorporated parts of the Power Macintosh architecture and mandated the use of Open Firmware (later also required for PReP systems).
To facilitate the booting of Windows NT on Open Firmware equipped systems (and by extension, CHRP), an ARC shim (VENEER.EXE) is included with Windows NT 3.51 and above, which implements an ARC environment on top of Open Firmware firmware calls. However, using Veneer requires a compatible firmware as well as an OF-aware HAL. This was originally the first step towards allowing dual boot between Windows NT and Mac OS on the same CHRP-compliant system. Such configuration with NT drivers for ADB keyboard and mouse was even demonstrated at the 1996 PC Expo by FirmWorks,Common Hardware Reference Platform Specification, FirmWorks. 9 October 1996. the company that developed Veneer together with FirePower Systems, although CHRP-compliant ADB drivers would not be compatible with existing Macintosh hardware.
Licensing Windows NT for use on Macs proper was even evaluated by Apple itself during its operating system crisis after the collapse of the Copland project. Gil Amelio is said to have been in talks with Bill Gates over this matter, with Gates promising to put hundreds of engineers on the project and to port QuickDraw to Windows NT.Hormby, Tom. The Rise and Fall of Apple’s Gil Amelio, Low End Mac. 10 August 2010. The proposal was still under consideration even in 1997, after Apple took over NeXT and Microsoft discontinued official support for PowerPC systems.Confusion reigns on Apple OS, CNET. 7 February 1997.
Apple is also known to have made special considerations in its hardware design connected to Windows NT support. Leaked internal Apple documentation relating to the blue and white Power Macintosh G3 mentions that its Open Firmware maps the super I/O chip registers to physical address 0x80800000 "to boot NT, just in case."BootROM Engineering Requirements Specification, Apple Computer Inc. 2000. Retrieved from the original on 2 May 2023. This is due to the fact that Veneer requires 8 MB of memory at virtual address 0x80000000 to be free as NT and its bootloaders expect RAM to be mapped at that address, and Open Firmware uses a 1:1 virtual-physical address mapping.
Some public Apple documentation also include references to Windows NT support, such as "Designing PCI Cards and Drivers for Power Macintosh Computers", which states multiple times that PCI-based Power Macintosh systems support little endian addressing in order to run Windows NT.Designing PCI Cards and Drivers for Power Macintosh Computers (Revised ed.), Apple Computer Inc. 26 March 1999. p. 569 "PCI-based Power Macintosh computers support little-endian addressing for several reasons [...] so that they can run operating systems (such as Windows NT) that require the underlying hardware to operate as if it were little-endian"Designing PCI Cards and Drivers for Power Macintosh Computers (Revised ed.), Apple Computer Inc. 26 March 1999. p. 578 "This effect [the PowerPC's little-endian mode] is desirable, for example, when Windows NT runs on a PCI-based Power Macintosh computer, because Windows NT requires memory to appear to be little-endian"
A ROM update for the Apple Network Server line of computers that would have implemented support for the PowerPC Windows NT port was additionally planned to be released until further development ceased in 1 April 1997 as part of the line's discontinuation,Floodgap ANSwers: The ANS FAQ, Floodgap ANSwers' Apple Network Server Resource. Retrieved 4 October 2024. two months after Microsoft dropped support for the PPC port.
== Unofficial port ==
In 2024, community member Rairii (a.k.a Wack0) has managed to successfully boot Windows NT 4.0 on a PowerBook G3 Lombard as well as under a fork of the DingusPPC emulator by using a custom ARC-compliant loader, HAL and drivers. His project, called maciNTosh, currently supports Windows NT 3.51 build 1057.1 and newer on New World Mac systems based on the Gossamer and Mac99 architectures.
Running Windows NT using the maciNTosh loader and drivers is currently the only possible way to run the PowerPC version under emulation.
== Notes ==
== References ==
Category:Specialized editions of Microsoft Windows