Red Hat To Support PowerPC, AltiVec

Steve Cowan writes "According to an article at MacCentral, Red Hat has announced that they will produce a GNUPro toolchain and cross compiler for AltiVec-enabled PowerPC processors (such as that found in the Power Mac G4). It will be interesting to see just what kind of performance gains this will bring, because many believe that the full potential of AltiVec is far from tapped."

Comments

Time to convert all those Mac users ;)

[IamTheRealMike]

Well, maybe. OS X is pretty nice, but that's another story.

Last time my Mac-lover best mate tried Linux the poor quality and performance of Linux PPC ports frustrated him. I pointed out that it's catch-22, having lots of fanatical MacOS users means very few try other operating systems, which means there's little incentive for linux companies to make decent ports and so on.

Problems were really apparent - for instance he tried a distro that was for PPC, but it had no Mac customisations what so ever. It just assumed he was using a 3 button mouse for instance. Hopefully if Red Hat do this properly, rather than just use a fancy compiler, OS X will have some competition on its home ground.

Re:The real worth here...

[Arker]

The real worth here lies in the fact that MacOS X is, let's not forget, essentially a UN*X platform.

I don't see what that has to do with anything. We're talking about porting the toolchain to the hardware. This has nothing to do with MacOs 10 at all. It's about Linux/PPC.

Linux/PPC has been hampered for quite awhile by the lack of good GCC support for things like AltiVec. Performance suffers from lack of optimisation. It sounds like RH is undertaking to fix that. This could be very cool - if they succeed then Linux/PPC programs will be able to take advantage of the full power of the PPC chips. AltiVec doesn't help with everything, far from it, but code which it does help will see truly impressive performance gains.

If you're not clear on what AltiVec is, try the link out. Basically it's MMX on steroids. It does everything MMX does, better, and some other things besides. It's really very cool tech, and it will be very nice to see Linux/PPC software finally taking advantage of it.

Isn't this just rolling back Apple changes?

[stevek]

IIRC, Apple (perhaps with motorola), has already put all kinds of AltiVec stuff into GCC for use as the OSX system compiler. Apple has been working on their own GCC tree, but has always been feeding some stuff back up to the GCC maintainers.

Isn't this just some marketing hype for RedHat (nee cygnus) just taking the patches already incorporated into Apple's GCC, and putting them into their commercial GCC release?

I don't know how GCC compares to Metrowerks' Compiler, or what Apple is using for different parts of their code (I dunno if MW does OBJ-C, so Apple would likely use GCC at least for that).

I suppose it wouldn't be too hard to look at the binaries and see what they're using.

-SteveK

Re:Isn't this just rolling back Apple changes?

[devphil]

Uh, no. Not by a long shot.

First, the changes that Apple made to their own version of GCC were not well thought out. Those patches can't simply be applied to the real GCC.

Second, I don't know what "commercial GCC release" you're talking about. The AltiVec patches have been going into the publiv version of GCC for weeks now. Check their mailing list archives for all the gory details.

Probably won't help mac fans.

[Eric Seppanen]

My guess is that they're doing this for embedded applications. Remember that Red Hat does a fair amount of business in the embedded arena, and PowerPC processors are pretty big in embedded applications. So while their work on the compilers will benefit everyone, including people running Linux on their Macs, this doesn't mean you're going to see a PowerPC version of Red Hat Linux any time soon.

Re:RedHat on new Macs?

[chainsaw1]

Motorola and IBM parted ways at the G4. The Power4 doesn't include AltiVec....IBM wanted to use the on-chip real estate for other things.

Also, the Power4 is a 64bit chip, and the G4 is still 32bit.

It will stay untapped.

[Erich]

Parallelism is really, really, really hard to do in a compiler. Intel has a hard time doing it even after spending millions for a compiler on their VLIW architecture. DLP is typically even harder than ILP for a compiler to do.

Compilers can typically do a pretty good job on sequential machines, but there is still a long way to go for getting good parallel code. Hand coding things is still the way to go for maximum performance.

That being said, the compiler can probably use it some, and having a resource available is typically better than not having the resource at all.

Re:It will stay untapped.

[RobertFisher]

I don't agree with this author's assessment. The type of "parallelism" involved in the AltiVec is SIMD -- single instruction, multiple data. It's the same kind of parallelism which Cray pioneered over 25 years ago. While in the early days, a great deal of hand-tuning was required, leading to such memorable Cray-specific replacement constructs as the vectorized Cray vector merges (CVMGT, CVMGZ, CVMGP, etc...) in place of non-vectorized If-Then's, great strides were made in Cray's compilers over the last few years. You could get very reasonable vectorized performance for most numerically intensive codes straight out of the compiler, without any modifications at all. With a bit of profiling and additional compiler directives, you could get excellent performance indeed.

The plain fact of the matter is that SIMD is MUCH, MUCH easier than doing distributed parallelization. It took Cray about 20 years to really get it right, so given how new the Altivec is, let's give Apple and company a few years to see how much they can accomplish.

Bob

Re:RedHat on new Macs?

[Brian Kendig]

'Darwin,' the FreeBSD-based core of OS X, is open source:

http://www.opensource.apple.com/

The interface, Aqua, isn't open-source because Apple wants to retain control of it.

I wouldn't call OS X 'largely untested.' It's directly based on NeXT's OPENSTEP operating system, which was known for being very stable and having great developer tools (the game 'Doom' was written on NeXT systems because of this), and OPENSTEP has lineage back to 4.3 BSD.

What's especially interesting is that Darwin runs on Intel PC's. This means that if Apple wanted to make Mac OS X available as an alternative to Microsoft Windows, all it would theoretically take is a recompile for the x86 architecture...

Re:Good way to make inroads.

[masonbrown]

And maybe, then Adobe will drop Photoshop on Windows, and make everyone use Linux. And maybe then, Microsoft will go out of business. And maybe then, Adobe will open source Photoshop, and make it free for everyone. And maybe then, Apple will give away its computers as free community property.......