Note this tip, and the related tips from Mac OS X 10.3 to 10.7 refer to Mac OS X Client. Mac OS X server questions more often are best answered by participants of the Server forums, as the limitations of Mac OS X Server can frequently differ.
Mac OS X 10.2 (Jaguar) or later require the correct firmware be installed. The Macs on this tip explain which do:
Be sure to backup your data first at least twice before installing any operating system. Shut down, and disconnect any peripherals before continuing with the installation. Read the info below to ensure you are compatible. Finally, you may need to use the Startup Manager to boot the operating system when the 'C' key doesn't work in order to get the installer to work or repair the disk before installation if the initial attempt to install fails. To determine if that repair is necessary, post to the forum, and someone will be able to help you to find out which repairs might be necessary.
Any Mac with a Firewire port, and a DVD drive can boot into Tiger, until new releases came out October 26, 2007. The full requirements are here:
Tiger introduced Spotlight to replace the old Find File, for some Panther's Find File is sufficient, and this tip explains
what you can do to maintain most of Tiger's compatibility without having to upgrade to Tiger:
version of Tiger that came on similarly labelled CDs, which are hard to find but are useful for Macs that can't boot off internal DVD discs (since they didn't ship with a DVD drive, or obtaining a bootable DVD drive is difficult) or external DVD discs, but do have Firewire. Those Macs include some of the PCI Graphics PowerMac G4, and the Blue and white G3 tower Macs.
10.4(.0 was omitted), 10.4.3 10.4.6 were all retail releases that did not say Upgrade, Dropin, or OEM. Though Intel Macs which started shipping with 10.4.4, can't take any of those retail discs, and must use the installer disc that shipped with them, until 10.5 (Leopard)'s release, at which point, they could use either a retail Leopard release, or the disc that shipped with them, until new Macs started shipping again December 15, 2008. If upgrading to an Intel Mac from a G3, G4, or G5, be sure to read this tip on migrating data. Also as part of the Intel Mac releases 10.4.5 to 10.4.11 (note 10.4.0, 10.4.1 are both older than 10.4.5) came in both PowerPC and Intel releases. Look at Apple menu -> About This Mac to determine if you have a G3, G4, G5 (all are PowerPC), or an Intel Mac. You can't
use the updater of one on the other.
Some Macs capable of having Tiger installed may benefit by having Leopard installed instead.
Read the tip below to find out if yours qualifies:
Also note, that iLife prebundled software started changing with Tiger. See this tip on what was prebundled and what wasn't:
Note also, Leopard removes Classic support, but not Mac OS X booting support for those that already had it.
See this tip to find out which Macs are able to boot into 10.5 and 9: