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Apple Makes the Switch: iMac G5 vs. iMac Core Duo

 by Anand Lal Shimpi on January 30, 2006 11:26 PM EST
  • Posted in
  • Mac
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35 Comments
Media Encoding Performance with iTunes and Quicktime

The encoding tests here are identical to the ones that we run in our CPU tests, except obviously run under Mac OS X 10.4.4 instead of Windows XP.  It's important to note that iTunes, Quicktime as well as the iLife and iWork suites are all Universal applications, meaning that they run natively on both PowerPC and x86 architectures.  The performance comparisons on these next few pages is done without any binary translation.

MP3 Encoding Performance - iTunes 6.0.2

The iMac G5 is pretty strong at floating point performance as we've already seen, so the fact that the Core Duo completed the 304MB encoding task in 3/4 of the time set off some alarms.  The 1.9GHz iMac G5 is a single core, single processor machine, while the Core Duo based iMac has two cores running at 1.83GHz.  The iTunes encoding test, like many operations in Mac OS X applications, is multithreaded, meaning that it takes advantage of multi-core or multi-processor systems.  So the question we need to be asking is how much of this performance advantage is due to the Core Duo's dual cores?

Luckily, OS X's processor panel provides a quick and easy way to disable one of the cores in the Core Duo machine, so we have a way of finding out.  With one core disabled, I added the non-existant iMac Core Solo 1.83GHz to the graph:

MP3 Encoding Performance Take 2 - iTunes 6.0.2

With an encoding time of 73 seconds, the Core Solo 1.83GHz is actually slower than the G5 1.9GHz.  Intel doesn't win because of a faster single core. They win because they have two cores where Apple could previously only put one. 

Let's take a look at Quicktime next; once again, this is the same test that's run in our CPU reviews.  This time around, I've included the Core Solo from the start:

H.264 Encoding Performance - Quicktime Pro 7.0.4

While the Core Duo wins the test, the Core Solo is actually slower than the single core G5.  We can cut Intel a little slack here, as it seems that Quicktime isn't very well optimized for their processors and Apple is reportedly working on fixing that, but the point is that we have now seen two cases where the G5 doesn't lose because it's a slower chip. It loses because there is only one of them in the iMac. 

Boot Time iLife '06 Performance with iMovie HD
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  • snookie - Friday, February 3, 2006 - link

    The article is very good but surprisingly makes the same mistake as so many other reviews which is to test with only 512MB of ram. The intel imac is a much better machine with more ram and it doesn't make sense to test it with the minimum amount. Also Universal apps are coming fast and furious on a daily basis. I've got 1.5 GB of ram in mine and lots of the little apps I use everyday are already UB and are nice and fast as is the OS and iLife apps. It won't be long before Windows runs on these as well as Linux with Red Hat promising support. Check out Bare Feats for some pretty nice benchmarks including games. Yes, Quake 4 will actually run at a decent speed as well as COD 2.
    http://www.barefeats.com/imcd.html">http://www.barefeats.com/imcd.html

  • csoto - Friday, February 3, 2006 - link

    Your only complaints stem from poor choice of models/configuraitons. The 20" unit will provide the added resolution, and BTO options allow up to 2GB on the Core Duo and 2.5GB on the G5 (although a 2GB soDIMM is listed at >$1K!). This is like me complaining that my mini van doesn't have a navigation system, because I was too cheap to buy the model that came with it :)

    Also, your assertion that the Core Duo is a "public beta" is absurd. You had zero problems running applications. Word from those around me that are testing Core Duos is that for most applications, you don't even notice Rosetta. Pro Apps users would complain, but they're never early adopters, because their apps always lag at least a few months behind the latest platform (remember the "multiprocessor plug-in" that allowed Photoshop to limp along for so long before a "MP-native" version was released?). This is a solid platform transition, likely exceeding the fairly solid (albeit far more daunting for the day) transition from 680x0 to PPC.

    Now if only VMWare would ship Workstation for Mac OS X, then I could ditch the Dell...

    Charles

  • Furen - Sunday, February 5, 2006 - link

    He says he already had an iMac so in order to compare the two I'm guessing he bought the closest-matching one possible. I would hardly do to have an 20" iMac compared with a 17" one in power consumption or running at a different native resolution. I do agree that the RAM limits the system insanely but he went for default specs rather you start improving all the draw backs each system has.

    The reason why he says this is like a public beta is not because Rosetta sucks or anything of the sort but because there are almost no universal binaries besides those shipped by Apple. Apple chose to bring these systems forwards (at first they had said the systems would come out mid '06, I believe) without having enough of a software base and that's a pretty big drawback.

  • jepapac - Wednesday, February 1, 2006 - link

    I was just wondering if the graphics adapter on the iMac is upgradeable since it is using pciexpress. Does anyone know?

  • aliasfox - Thursday, February 2, 2006 - link

    I'm guessing its actually the laptop X1600 in the iMac, soldered onto the motherboard. Unfortunate, yes, but given the primary audience that the iMac is targeted at, I'm not surprised.

    Your average home user would rather buy a new $600-1000 box instead of dropping ~$500 for more RAM, a bigger hard drive, new graphics, and a faster processor.

  • Eug - Thursday, February 2, 2006 - link

    quote:
    I'm guessing its actually the laptop X1600 in the iMac

    Why? Previous iMacs used desktop GPU parts.

  • aliasfox - Thursday, February 2, 2006 - link

    I read somewhere that the 9600 in the second generation iMac G5 was a laptop part, and I therefore assumed that since Apple used the same GPUs in the iMac that it used in PowerBooks (GeForce FX5200, Radeon 9600, X1600), it was sourcing the same parts for both lines.

    Also, I've never read about an integrated 9600 or FX5200 as a desktop part. I might be mistaken though.

  • nizzki - Tuesday, January 31, 2006 - link

    Any idea which compilers apple has used for their apps? For example, for the PPC apps I assume apple uses the IBM compiler heavily optimized for PPC instead of GCC.
    If that is the case, with the intel compiler for osx is in beta, the current somewhat lackluster performance of the core duo might be skewed in PPC's favor. This would be further exacerbated if Apple used GCC to compile the macintel apps, since it is unlikely to be heavily optimized for the core duo architecture.

  • Commodus - Tuesday, January 31, 2006 - link

    Just a heads-up, Anand: the Core Duo iMac is the first iMac model to support desktop spanning, not just mirroring. So if you want, you can hook up even a 23" Cinema Display and get a huge amount of extra workspace. I'd probably only do that with a 20" iMac and the 256 MB video memory option, though.

  • ingoldsby - Tuesday, January 31, 2006 - link

    Perhaps it's just me, but the non native apps I run seem to run at about the same speed as they natively ran on my G5. While the universal binaries run much faster.

    I would love to see this comparison revisited with a realistic amount of memory in the machine (ie. 1gb+) instead of limiting the machine to 512mb.
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