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Since I repaved my MacBook with Snow Leopard this morning, I was about to reinstall one of the applications I use, Adobe Flex Builder 3. When I opened FB3's installer, the following was displayed:

To open __, you need to install Rosetta.  Would you like to install it now?

(Dialog says: "To open FB3_Mac_Installer, you need to install Rosetta. Would you like to install it now?")

Questions:

  1. What exactly is Rosetta? (I have an idea, but your expert answer is probably better than my understanding.)

  2. Why don't I already have Rosetta included with my fresh from-scratch Snow Leopard install? It looks like Rosetta comes from Apple. Why would Apple decide to not include it? Would this have been an optional install from my Snow Leopard DVD, or is it only available online from Apple?

  3. Why would a relatively recent installer such as Adobe Flex Builder 3 require Rosetta? I've installed many other packages already and hadn't seen this message, until now. Is Adobe doing something silly?

  4. Is there any performance or other impact or concern with having Rosetta installed?

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5 Answers 5

up vote 12 down vote accepted

What exactly is Rosetta? (I have an idea, but your expert answer is probably better than my understanding.)

Rosetta is a piece of software through which PowerPC code can be run on an Intel Mac.

Why don't I already have Rosetta included with my new Snow Leopard install? Why would Apple decide to not include it? Would this have been an optional install from my Snow Leopard DVD, or is it only available online from Apple?

Snow Leopard is Intel-only. Apple essentially wants the few remaining developers who still have PowerPC-only software to recompile it for Intel. Rosetta is an optional install which is available on the Snow Leopard DVD.

Why would a relatively recent installer such as Adobe Flex Builder 3 require Rosetta? Is Adobe doing something silly?

Adobe's Mac range is possibly the worst-made set of applications that anybody actually uses. See Adobe UI Gripes for more Adobe hating.

Is there any performance or other impact or concern with having Rosetta installed?

Only when you're running PowerPC code. Simply having it installed will not decrease performance. There is little reason for you not to install it; it's a small package that allows some software to be run slowly that otherwise couldn't run at all.

I've made this CW so please edit this if you have something to add.

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Thanks for addressing each point. –  Chris W. Rea Aug 30 '09 at 2:43
  1. Rosetta allows your computer to run PowerPC-only code, i.e. old code which pre-dates Apple's transition to Intel CPUs.
  2. Rosetta ships with your Snow Leopard DVD but it's an optional install. Apple probably thinks that almost all software is translated to Intel nowadays.
  3. Because Adobe didn't ship an App with Intel code. (Some Epson printer drivers also still use PPC code and require Rosetta even on Snow Leopard.)
  4. Of course native code would be much nicer/faster. I'm not sure if only the installer requires Rosetta or the application it installs. If only the installer itself requires Rosetta it's no big deal.
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Thanks for addressing each point. –  Chris W. Rea Aug 29 '09 at 20:24

According to the Adobe website only the CS4 product range has been certified as Snow Leopard compatible and the compatibility list available here shows that Flex 3 is still untested.

Rosetta is the technology that allows PowerPC applications to run on Intel Macs. From everything I have seen thus far this has been removed from Snow Leopard by default, and based on your screenshot will install when required. Potentially this will be removed in the next OSX version.

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Rosetta is a lightweight dynamic translator for Mac OS X distributed by Apple. It enables applications compiled for the PowerPC family of processors to run on Apple systems that use Intel processors. Rosetta is based on Transitive Corporation's QuickTransit technology, and it is a key part of Apple's strategy for the transition of their Macintosh line from PowerPC to Intel processors as it enables pre-existing Mac OS X software to run on the new platform without modification.

The name is likely a reference to the Rosetta Stone, whose discovery made it possible to comprehend and translate Egyptian hieroglyphs.

Source: Wikipedia

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Flex Builder 3 does not require rosetta to run. Dumb Snow Leopard thinks it does. Just Cancel out and it will be ok.

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Thanks - I suspected it's only the installer program requiring it. Flex Builder 3 is built on Eclipse, which is Java-based, so it would make sense that it has no native-code dependency on the PowerPC. –  Chris W. Rea Aug 31 '09 at 11:35

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