Re: [Audacity-devel] FAQ on 64 bit Audacity

[Richard A. <ri...@au...>]

On Fri, 2008-08-29 at 14:55 -0500, Dawson Written wrote:
> > I have not mentioned Mac. My understanding is that basically this just
> > works in OS X 10.5 - if the Mac is 64 bit, 32 bit Audacity works whether
> > the sound device is 32 bit or 64 bit. Corrections welcome though.
> Can't help you there. You just making that one statement, already shows 
> you know more than I. :-D

I would suggest that we split the answer by operating system, so that
each of them can be simpler and easier to follow.

The state of play on Mac is actually simpler than elsewhere, because
Apple have worked very hard on interoperability.

There is only one version of OS X, which can be installed on 64-bit or
32-bit hardware. It is unlikely that users ever have to install their
own drivers, but if they do then there is a single set of drivers for
that OS X version, regardless of hardware. So complications like 32-bit
OS on 64-bit hardware don't show up.

For OS X 10.4 and older, there is no such thing as a 64-bit
application. All applications are 32-bit code. They may well use 64-bit
parts of the run-time environment, but that is entirely hidden under the
bonnet of the operating system.

In 10.5 it is possible to build a graphical 64-bit application, which
will then be restricted to 64-bit installations of OS X only. This is
the exception rather than the rule, with 32-bit applications being the
norm. Most applications that do have a 64-bit build will do so via an
extended Universal Binary, which will in fact have three or four copies
of the application in it, covering 32-bit PPC, x86, IA64 and 32-bit PPC
architectures (the last being a rarity).

The Audacity releases are a Universal binary for  at least 10.4 and
newer, so they contain 32-bit PPC and x86 code, and will run on any OS X
system on any hardware that is supported by the OS.

The sound device is not going to be 64-bit (you can get 64-bit PCI
slots, but they are like hen's teeth), the hardware in almost all
systems with 64-bit CPUs is accessed over 32-bit buses. The important
thing as Dawson has said is that the drivers must match the OS kernel -
trying to load 32-bit drivers into a 64-bit kernel or vice versa is a
recipe for disasters (It could be argued that an OS design (executeable
format?) that makes it possible to even try is a disaster zone, but that
is a separate issue).

Richard