[ros-kernel] Different Hardware Architectures

[Mike Nordell]

mccall wrote:

> I currently have a few different Macintosh PowerPC machines so I am
> unable to run the OS at the moment, but I was wondering wondering
> how portable the ReactOS kernel is to different hardware architectures?

The goal I believe is to have it at least as portable as the NT kernel -
meaning 95-99% code requiring just a recompile. The rest 1-5% would AFAIK
only be endianness issues, low-level assembly code required and hardware
platform differences.

If one knew every aspect of a PPC Mac from the hardware perspective, my
guess is that at least the kernel (i.e. ntoskrnl + HAL, the Hardware
Abstraction Layer) could be made running on such a machine within a month or
two. If there was something similar to plain VGA that could probably also
work at that time. For the user-mode components, I believe it'd only be
32/64-bit and endianness issues, things that should be fixed anyway.

> I know that there may not be much of a demand for ReactOS on
> PPC machines,

I believe this can be the chicken-and-egg problem.

> but it may be fun to help out, and keeping a different
> architecture in the build process could also help keep the kernel in
> good shape for porting to other architectures on the future, much as
> Apple does with its Darwin kernel.

I for one welcome such an initiative, for many reasons.

> Has the kernel been written with multiple architectures in mind?

Sort of. There are currently some places in the code making hard-coded
assumptions, such as where the kernel/user-mode address-space VM-"line" is
to be drawn, but they are scheduled for termination anyway. Starting a PPC
port would surely illuminate the problems and escalate the importance to fix
them.

> Is anyone else interested in getting ReactOS running on PPC machines?

Out of (currently) academic interest, I am. Should I ever experience the joy
of laying my hands on a PPC machine that would obviously become a personal
interest too.

> I would be intrested in donating hardware if there are any other
developers
> interested, I probably could get quite a few PPC Macintoshes for people if
> needed - they are really cheap on eBay!

Have I ever seen an offer almost too good to be true, this must be it.

Unfortunately I've personally got just above zero experience with any PPC
platform, and I believe to take a serious stab at such a port one would have
to be at least reasonably familiar with the hardware platform and its
chipsets. Probably lots of information can found by looking at other
kernels, such as the mentioned Darwin, but still... not even knowing the
instruction set of the target CPU would initially have a somewhat chilling
effect on porting speed.

Yet, I'm personally intrigued by your proposal and will take it under
serious consideration.

/Mike