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  • The Secret of Improving Rosetta’s Performance

    January 28th, 2006

    Way back when, when the first Power Macs hit the streets, I found performance with older Mac apps to be perfectly awful. It seemed as if I had gone back two generations in chip design, from the PowerPC to the 68030, and that was being generous. So when another emulation scheme was announced, Rosetta, which allows Intel-based Macs to run PowerPC software, you had reason to be concerned.

    Although they are being coy on the details, Apple’s Rosetta technology is based on QuickTransit, an emulation method from Transitive Corporation. When I taped an interview with Transitive CEO Bob Wiederhold for this week’s episode of The Tech Night Owl LIVE, I had to forgive him if he danced around a few key details because of the company’s deal with Apple.

    But here are the basics: When you launch a PowerPC application on a MacIntel, Rosetta translates chunks of code into memory. The code is reused as needed when various application features are run. How much memory? Well, in general, according to Wiederhold, their technology will exact a 50% overhead. So, as an example, if a PowerPC app needs 128MB to run, another 64MB will be required for emulation. You’ll need to think about this overhead carefully when you decide how much memory you need to get the best performance for your new MacIntel.

    Now Transitive’s own presentation materials on their technology estimates that Rosetta will run at sixty to seventy percent of full processor speed. The tests published so far by Macworld and others are less optimistic, putting the speed hit at fifty percent. So why the disparity? Is Transitive fudging its numbers just a little bit?

    Well, the magic bullet may very well be RAM, and most of the new iMacs tested so far appear to come with the default 512MB allotment. What if it was increased to, say, 1GB? Good question, and I’ll be interested in seeing the comparisons as testing of the new products continues. Now in normal circumstances, particularly if you stick with Apple’s own applications that have been ported to Universal status, and older apps with modest memory needs, performance should be pretty decent with the stock configuration.

    When it comes to Adobe Photoshop and other high powered software, things get muddy. Photoshop, for example, loads an entire image into memory, large color illustrations, for example, could suck up RAM with abandon. You might just want to open Mac OS X’s Activity Monitor, which is located in the Utilities folder, and monitor the requirements of different applications as you move from one to the other. This will help you decide whether to max out the memory of your new MacIntel.

    Now in the end you can’t expect miracles. Whether Rosetta runs at half the speed of the native processor or up to seventy percent, as Transitive claims, isn’t all that significant in the scheme of things. Mac OS X for Intel seems to be pretty snappy, and it’ll do its thing at a pretty good pace. Sure, Photoshop rendering functions won’t be so swift, but if you’re upgrading from a very old Mac, it’ll still be a lot faster than what you’re used to. Bear that in mind when you look at the reviews of the MacIntel version of the iMac. Remember that the comparisons are usually being done against current hardware, so you have to be realistic as to how those results will impact you.

    As I said, the Intel-based Macs are among those rare personal computers that will continue to become faster over time, as more and more developers make Universal versions of their software, and continue to optimize their code. Already well over 300 applications have made the voyage, and more are added every single day. It won’t be long before the total will exceed 1,000.

    However, the sprawling productivity applications with ancient code bases will require lots and lots of work to bring across the finish line. Quark Inc. has already done a lot of the heavy-lifting, which is why a public beta of a Universal version of QuarkXPress 7.0 will be available real soon. However, I don’t expect to see native versions of Adobe’s Creative Suite until this fall at the earliest, if then. Adobe not only has to update its software in Universal form, but it’ll need to be compatible with the forthcoming Windows Vista, and what that may require is anyone’s guess at this point.

    Microsoft will no doubt face a similar dilemma. Months and months of work, and one only hopes that next version of Office will also sport a generous selection of new features to justify the upgrade price you’re going to pay.

    For now, however, if you’re interested in buying a new iMac or ordering the MacBook Pro, you’ll want to approach the process realistically. Don’t shortchange yourself on RAM, especially if you have a bunch of PowerPC applications that will keep Rosetta real busy.



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