If I have an iMac G3, G4, or G5, can I upgrade to 10.6 , 10.7, 10.8, or 10.9 (Snow Leopard, Lion, Mountain Lion, or Mavericks)?
10.5.8 is the newest operating system available for G5s, and iMac G4s with a minimum of 1 Ghz (800 Mhz is less).
For other Mac models that minimum is 867 Mhz on a single processor, and dual 800 Mhz does not count. Third party software known as LeopardAssist can allow older Macs to use 10.5.8. Note, upgrading to 10.5 removes Classic compatibility. Adding an external Firewire drive, or partitioning the hard drive with 10.4.11 or earlier continues to allow Classic support. This is covered in more detail here:
10.4.11 is the newest operating system for those with a Firewire port on their Macs who are not at least 867 Mhz on a single processor.
XPostfacto is a third party software that allows older Macs to use 10.4.11.
10.3.9 is the newest operating system for those without a Firewire port on their iMacs.
10.6, also known as Snow Leopard is only available to those with an Intel processor. The G3 is an IBM processor, the G4 a Motorola processor, and the G5 is an IBM processor. And 10.7, also known as Lion is only available to those with an Intel Core2Duo, Core i3, i5, or i7 processor. For more about the 10.6 limitations see:
and the 10.7 limitations, see:
This user tip was generated from the following discussion: If I have an iMac G3, G4, or G5, can I upgrade to 10.6 or 10.7?