Classic, Rosetta, and 32/64 bit revisited.

Last Modified: Nov 2, 2012 12:06 PM
Older software on newer machines is a frequent question on this board, which has been covered in the User Tips section before. To make it more current, the following information has been updated.


Classic is an environment within Mac OS X on PowerPC (PPC) Macs running 10.4.11 and earlier that allows most Mac OS 9 applications to run. This is not to be confused with "booting into Mac OS 9." Mac OS 9 booting supports all Mac OS 9 compatible applications and drivers, where Classic does not. See questions 7 and 9 for more info.


Rosetta is a background application that integrates most PowerPC Mac OS X applications in an Intel CPU Mac running Mac OS X in such a way that both Intel Mac OS X applications and PowerPC Mac OS X applications can share the same machine.  Rosetta is not to be confused with Rosetta Stone, the third party language translation and teaching software of nearly the same name.


Snow Leopard offers 64 bit computing for some applications and the operating system itself. This can affect which peripherals and applications will run.


The limitations of both are outlined below:


1. Can Snow Leopard run software written for PowerPC Macs?


Yes, if it was written for Mac OS X and does not require contextual menu plugins, PowerPC plugins, or PowerPC drivers. Rosetta is an optional install on the DVD for Snow Leopard, and is offered when PowerPC software is run for the first time on a Snow Leopard installed Mac if it wasn't installed initially.
Click on Applications that are installed once and select Get info in the File menu to checkoff Rosetta, if you believe it might work better in Rosetta, than Intel native mode.

Sometmies when 10.6 is installed, Rosetta, the application that allows PowerPC programs to run will not automatically install.  In those situations, you can manually install Rosetta from the 10.6 installer disc.  The following quote explains how to install it manually:


Insert the Mac OS 10.6 installation DVD When the DVD is mounted, select “Optional Installs” then “Optional Installs.mpkg”

Follow the onscreen instructions for agreeing to the software license and selecting the hard drive for installation.

In the “Installation Type” step, select the box next to Rosetta from the list of applications presented. Continue the installation process.

After successful installation, a confirmation message will appear.


These instructions appeared on


Note: if you have Rosetta applications installed during an upgrade install of 10.4 or 10.5, Snow Leopard installer will automatically include Rosetta in its installation.


2. Can Lion run software written for PowerPC Macs?

No.  Limited success has been done with virtualized software running Snow Leopard Server.  However, I would not depend on it,

and if your Mac's model was refreshed on or after July 20, 2011, it likely won't be able to run Snow Leopard or earlier, or Rosetta.

See Question 3 for more info on this topic.


3. Can Snow Leopard run on Lion prebundled Macs?
In some rare cases, such as has been documented in this link:

and the bottom of this link:


If you suspect the need to run Rosetta is there, get a used or refurbished Mac that was released prior to July 20, 2011, with the original installer discs.  If it is older than March 29, 2010, and an Intel chip with 1 GB of RAM you can use the most recent Snow Leopard retail installer to install Snow Leopard, instead of trying to find the harder to get prebundled discs, if the Mac doesn't come with prebundled discs.  For more on


4. Can Intel Macs run PowerPC software?


Yes, if Rosetta is installed. It is preinstalled in 10.4.4 through 10.5.8.
Snow Leopard installation is described in question 1.


5. Can Intel Macs run Classic?




6. Can Snow Leopard run Classic?




7. Can PowerPC Macs run Snow Leopard?




8. Can Leopard run Classic?


No. However, PowerPC Macs with a Firewire external bootable hard drive running 10.4.11 or earlier, or a second partition with 10.4.11 or earlier can have the Classic environment installed on them. A second internal hard drive with 10.4.11 or earlier is yet a third way to approach this problem.  Classic is not the same as booting into Mac OS 9. Like Rosetta, it has limitation for running older plugins and drivers. Partitioning is described here:


9. Are there Macs that can run Leopard and boot into Mac OS 9?


Yes, see this user tip:


10. How do you install Mac OS 9 on a Mac released post-July 2002, with a PowerPC chip?


These directions help both in enabling Classic, and booting into Mac OS 9 with the Macs that support it. Follow the restore directions with the discs prebundled with that Mac here:


Unless your Mac is prebundled with 9.2.0 or earlier, there is no retail Mac OS 9 installer disc that will install Mac OS 9 on your machine. This article tells you what is prebundled with which Mac:


July 2002 and earlier Macs come with their unique Mac model specific 9 installer disc if they came with 9.2.1 or 9.2.2.


11. How do I boot into Mac OS 9?


Go to Apple menu -> System Preferences -> Startup Disk and select the Mac OS 9 System Folder. This is only available to Macs made pre-2003, except the pre-Firewire 800 PowerMac G4 MDD and G3 iBooks.  To tell if your PowerMac G4 can boot into 9, look at the back panel, and see if there is a Firewire 800 port, such as is shown on this image:

If there is none, then you have a machine capable of booting into 9.

Also if Mac OS X was initially installed on the machine without Mac OS 9, you may have to erase the Mac, and install Mac OS 9 drivers to enable Mac OS 9 booting when you install Mac OS 9 on it, by following these directions:


12. How do I boot into Mac OS X?


If it is on the same partition as Mac OS 9, hold the "X" key upon boot. Otherwise use a 9.1 or later Startup Control Panel from Apple menu -> Control Panels folder to select the Mac OS X folder if it is installed. This article explains how to get it on earlier Mac OS 9 installs:


13. How do I run Classic?


As long as you have 10.4.11 or earlier on a PowerPC Mac, you can do the following:


Go to Apple menu -> System Preferences -> Classic. Unlike Rosetta, Classic will show its status in its own window. Additionally if an Application's File Type in the Finder shows as Classic Application, then it will run in Classic. Some applications will allow you to force run themselves in Classic, by clicking on themselves once in the Finder, and selecting Get Info in the File menu, and checking "Open in Classic Environment."


Additional clues you are running Classic include (some of these may be modified by third party addon software:


You won't have rebooted, but your Apple menu is rainbow colored (on the upper left)


When you click on the Apple menu it will reveal a Chooser, and Control Panels instead of Startup and Shut Down.


The application will not only say Classic Application in the Finder File type, but also show a way of increasing its allocated memory in the Finder, as shown here:


Apple menu -> System Preferences -> Classic will show that Classic is runnning.


A Mac OS 9 logo will appear in the Dock when you launch a Classic application


Classic menu in the System Preferences can show if Mac OS 9 is running in the menubar with a Mac OS 9 logo.


If you have 10.5 or later on a PowerPC Mac, scroll up and read tip limitation #9.


14. How do I disable 64 bit computing, and use only 32 bit?


Some third party drivers will misbehave if System Preferences in Snow Leopard (10.6) is set for 64 bit. Similarly, some applications behave better if they are not running in 64 bit. To toggle these settings:


Click once on System Preferences in your Applications folder, and click on Get Info in the File menu. Check the checkbox Open in 32 bit mode, to disable 64 bit computing on System Preferences. You can do the same for any other application that has 64 bit and 32 bit capability built-in, by clicking once on the application, and selecting Get Info.


15. These Macs support 64 bit natively on Windows Boot Camp:


Just because your Mac doesn't have 64 bit Windows support through Boot Camp does not mean your Mac doesn't support 64 bit addressing.  IBM G5s, Intel Core2Duo, Core i3, i5, i7 and Xeon processors all have 64 bit support built-in. Some Macs because of their age will not address more than 3 GB of RAM, or 2 GB of RAM, but still support 64 bit based applications that support their processor. Motorola G4 processors have limited 64 bit support with Altivec vector processing.  G3 and older, and Intel CoreDuo, CoreSolo have no 64 bit support.