• Before You Buy a MacIntel: A Rosetta Performance Update

    March 25th, 2006

    In the past, processor emulation has gotten a bad rap for good reasons. Consider Microsoft’s Virtual PC for the Mac, which epitomizes languid performance. But if you think it’s bad, try some of the other PC emulators, even the ones that are loudly proclaimed as Universal binaries fully compatible with MacIntels. Of course, way back in the days when Apple switched to the PowerPC, its emulation performance for older 680×0 software also turned a fast Mac into a slug. In those days, it took years for the software to catch up, and, no, I don’t believe it was a key factor in Apple’s lost market share.

    So you would have had modest expectations for Rosetta, the emulation environment that lets you run PowerPC software on an Intel-based Mac. But the firm that supplies at least a portion of the technology, Transitive Corporation, has made far more robust claims, such as performance approaching 70% to 80% of the native processor. However, the reality seems noticeably less, according to most of the folks who have actually benchmarked Rosetta. It’s speed hit is more in the 50% range, give or take a few, and sometimes worse.

    Now I haven’t actually attempted to confirm these published results, but they are sufficiently widespread and come from enough authoritative sources to accept at face value. It means that your spanking new MacBook Pro with a 2GHz Intel Core Duo processor, acts more like a computer with a 1GHz duo core processor when you uses Microsoft Office or Adobe Photoshop. This may sound disappointing, but it really shouldn’t be.

    Just what kind of Mac are you replacing? Forgetting the various differences between the PowerPC and Intel chips, if your computer was rated at less than 1GHz, you’re still getting a speed boost on your emulated software. And it’s just a stop gap. You can rest assured that both Office and Photoshop will go Universal some time in the next year. Other applications are being updated nearly every single day. Sure, the sooner the better, but I can’t see typing in Word any faster than I do now, so I wouldn’t consider emulation a significant turnoff unless I was working on lots of large documents with embedded documents.

    There are things you can do to enhance Rosetta performance, however, and the first is to max out RAM. According to Transitive, its technology typically exacts a 50% memory overhead on an emulated application. In the real world, if Photoshop, for example, needs 128MB of RAM to run efficiently, add another 64MB for Rosetta to do its thing. When you factor in the requirements of Mac OS X for Intel, and any other applications you might run simultaneously, you can see that a 512MB MacIntel is apt to bog down in virtual memory land before long.

    So if you need to run one or more resource hungry applications in Rosetta, consider 1GB of RAM the minimum for optimum performance. If you’ll live most of your digital life in iLife ’06, Safari and Mail, the standard memory allotment won’t bog you down, even on the Mac mini, which allocates 80MB for its integrated graphics.

    Also don’t forget one thing that commentators have largely ignored, and that is that Rosetta is at version 1.0 for all practical purposes. Over time, it’s quite possible that Apple and Transitive will find ways to make it run faster, and don’t be surprised if one of the main features of Mac OS 10.5 Leopard is a 10 to 20% performance boost for PowerPC emulation. Of course, I don’t have any real inside information to offer, but Apple has managed to eke out speed enhancements on every single major upgrade of Mac OS X so far, so don’t be surprised if more gains are possible in a number of areas.

    I don’t for a moment believe that Apple has done the best it can. The Intel transition is moving a whole lot faster than anyone had the right to expect, and could likely be over by late summer. Did Apple have enough time to maximize the efficiency of Rosetta emulation? Probably not. The goals were probably compatibility, reliability and stability, with performance optimization rating lower on the list. For most of you, I bet it works just fine as it is now. Believe you me, if you haven’t tried a MacIntel, I can confirm that you usually observe no visual or visceral indication that Rosetta is working. It’s that seamless. Yes, a little closer scrutiny will reveal that the emulated applications take longer to launch, and such things as scrolling might seem ragged. None of this will require the stopwatch that seems always to be in the hands of product testers. But, unless you’re running a Photoshop filter on a big file, the speed hit won’t strike you right between the eyes.

    In fact, the fact that Mac OS X seems speedier on Intel will make your general computing experience seem better. That client of mine, for example, who had has MacBook Pro set up a few days ago, can’t stop singing its praises, even though he still uses Microsoft Entourage to retrieve his email. And that’s the way it is.

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