Re: Some questions about build.sh, machine, -u and tools

[Martin Husemann <martin%duskware.de@localhost>]

On Wed, May 05, 2021 at 10:57:56AM +0200, Rocky Hotas wrote:
> MACHINE is defined in the paper as a platform (par. 5.1).  Intuitively,
> yes, MACHINE seems related to a whole computer (so, a collection
> of hardware devices with its standards and conventions) and
> MACHINE_ARCH is somewhat more specific, being related to a specific
> CPU, but MACHINE is still a somewhat blurry element to me.

A MACHINE is a concrete thing, it belongs to a broader group of similar
(but not identical) other machines of the same MACHINE_ARCH.

How wide the range of MACHINE_ARCH goes, depends on details, e.g. there are
lots of very different MACHINE (mac68k, atari, amiga, sun3, next68k, mvme68k...)
for MACHINE_ARCH = m68k. This is because we made userland compatible.
Similar for MACHINE_ARCH = powerpc.

However, due to tiny but important instruction differences, we have
probably more earm* MACHINE_ARCH's than MACHINEs for MACHINE_ARCH=m68k.

So in short: MACHINE_ARCH may be shared with other MACHINEs. Userland
programs (ignoring device specific ioctl helpers) do not care about
MACHINE but only require the MACHINE_ARCH.

Martin