Re: Question about the various supported build architectures...
Re: Question about the various supported build architectures...
- Subject: Re: Question about the various supported build architectures...
- From: Doug Hill <email@hidden>
- Date: Wed, 5 Mar 2008 15:24:54 -0800
Hello Terry,
I would say the main reason to use these various flavors of PPC is if
you were targeting that specific CPU and would get some benefit from
doing this. It's kind of like setting mtuneG4 versus mtuneG5. If you
don't have any machine specific requirements for your product then you
can probably just use PPC/PPC64 and it would be fine. However, if you
know you will only ever run on a G5 using PPC970 could be helpful. But
unless you have specific requirements for a particular machine, it's
generally recommended to use the more general setting to get access to
the largest installed base and not unnecessarily exclude older machines.
What all of these settings do is probably very low-level and have to
do with linker optimizations and code generation. I don't think it has
to do with just math related code but code ordering, CPU specific
instructions, etc. Unless you have very intimate knowledge of the
specific CPU architectures and implementations the details may not be
all that useful to you.
Doug Hill
Oracle Corp.
On Mar 5, 2008, at 1:56 PM, Terry Simons wrote:
Hi,
Is there a document somewhere which explains the various advantages/
disadvantages of supporting the various architectures in an Xcode
build?
For instance:
What's the difference between straight "ppc" vs "ppc970" or
"ppc7400"? I know that all 3 are supported when building against
10.4, and I'm assuming that the only difference here are CPU
optimizations that are specific to a given CPU type? Is there a list
of the differences somewhere? Is there any advantage to using ppc970
and/or ppc7400 in addition to ppc for an application which isn't
necessarily math-heavy, or is it recommended to go with the safer more
generic ppc option?
Extending this to 10.5 and later SDKs... Besides the obvious 64-bit vs
32-bit differences with ppc vs ppc64 and i386 vs x86_64, is there a
document describing the various iterations? If I build an i386
application that runs on an x86_64 native system, what are the
performance implications? Is there a big difference between the
native actual architecture in this case? What I mean here is, if my
application is not math intensive, am I going to gain a perceivable
bump by building native 64-bit vs building 32-bit?
Are people building Universal Binaries with all of the supplied
architectures, or is it generally advisable to choose the smallest
number of architectures to minimize potential problems?
I'd like to read up on this more if there are docs available.
Thanks!
- Terry
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