What is known for now from different sources:
- WoA 8 would require UEFI to boot (instead of BIOS on x86), ACPI is required too. So no WoA to existing devices (they don't have UEFI/ACPI and I don't think that anyone would waste his time on emulating them).
- No native support for x86 apps on ARM, nor ARM apps on x86. Only .NET apps would work in both worlds.
But it is possible to create an emulator similar to DosBox that would run native x86 programs on WoA and, for example, I'm currently working in this direction.
- Though existing C++ apps can be recompiled for ARM from sources, it is not a 100% working solution. Current VS11 contains a rather limited set of ARM libraries - no DirectX libs earlier than 11, no import libraries for NtDll.Dll and similar DLLs.
I don't have access to any WoA builds, so I can't check whether these features are completely removed from ARM, or those LIBs are just not present in current VS11 build. But at least now we can compile test apps for ARM and analyze the code (though we don't have where to execute them yet).
- Native WoA programs use THUMB2 instruction set (ARMv7 and above). Though ARM instruction set would be supported too.
- According to "Microsoft Portable Executable and Common Object File Format Specification v8.2" WoA machine type in PE files would be 0x1c4, and some new relocations types are added (for example IMAGE_REL_BASED_ARM_MOV32T = 7). IDA understands such EXE files, though complains on relocs.
- SEH is implemented in a different way than on x86 (similar to x64, google for RtlAddFunctionTable to get the idea).
- WoA is more secure by default. For example TPM can be rarely found on x86, but it would be required on ARM.
- Most of existing drivers are source-code compatible with ARM (of cause if not using x86-specific stuff). But ARM would never allow to load unsigned drivers (unlike x86 Win7/8).
- As platform is completely new - all ARM drivers would be added to windows update site to simplify our life. Some obsolete hardware like 1394 is not implemented at all, so there would not be so many drivers for ARM llike for x86.
- All binaries would be the same for all SoC providers.
- No "native" ARM VisualStudio - developer tools are x86 only.
WoA requirements from different sources:
- 10.1” display with 1366x768 min resolution (though smaller screens may be supported with reduced functionality)
- Volume Control, Windows, Rotation, Lock power buttons
- Dual core CPU with hardware accelerated GPU
- at least 1 Gb RAM
- min 16 Gb fixed storage
- 100mW idle power in standby
- there are rumors that there would be standart "Phone call API" ("Apollo" UI)
Does anyone have access to ARM WDK? It would definitely contain a complete set of import libraries and would provide lots of info on WoA internals in headers/documentation. Seems that Windows 8 WDK on MSDN does not have ARM tools