Mac OS X10.3 - Minium Requirements...

Requirements for Mac OS X 10.3

Mac OS X 10.3 works with these Macintosh computers:

Power Mac G5 (all models)
Power Mac G4 or Macintosh Server G4 (all models)
Power Macintosh G3 or Macintosh Server G3 that have built-in USB ports
iMac (all models)
iBook (all models)
PowerBook G4 (all models)
PowerBook G3 (Bronze Keyboard models only)

1. Not all computers listed can use earlier versions of Mac OS X. Usually, the earliest version of Mac OS X a computer works with is the version it ships with. For more information, see this document.

2. Identifying PowerBook computers: All PowerBook computers that work with Mac OS X have a large, white Apple logo on the outside of their display lids.

3. Computers with microprocessor upgrade cards do not work with Mac OS X. Though Mac OS X may install and appear to function normally on some computers with third-party microprocessor upgrade cards, Apple does not provide technical support or assistance for Mac OS X when used in this way. Contact the manufacturer of your microprocessor upgrade card for support information.

4. If your Power Macintosh G3 or Macintosh Server G3 computer has a build-to-order (BTO) 128-Bit 2D/3D Professional Graphics Accelerator Card, you should read "Mac OS X 10.0: 128-Bit 2D/3D Professional Graphics Card Causes Kernel Panic".

Additionally, the computer should have:
128 MB RAM (memory)
At least 1.5 GB free hard disk space
Note: For Mac OS X 10.2 or later, 3.0 GB is the recommended minimum. The exact amount required depends on your computer and how you install Mac OS X (default versus custom installation, for example).
Mac OS 9.1 or later for Classic applications