swordbreaker55
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Re:Running 10.4.11 on an Intel Xserve (Early 2008) - 2008/02/18 01:27
In general, the version of Mac OS shipped with a particular model is the absolute minimum OS allowed to run on that model. Allow me to explain.
During the Mac's "classic" period (prior to 2002), the OS could only be installed if it had either the proper enabler (System 7.x), or Mac OS ROM (7.6-9.2.2) present. A custom ROM data file would be pressed into each model line's restore media so that lower versions absolutely could not start in those lines. These same CDs would also have contained machine-specific programs and extensions that were needed at the time of manufacture. Later version installers would have the needed ROM data to boot older models, as well as a larger and more current library of extensions which included the machine-specific items. Code would have been placed in the new installer to autodetect the machine type and load the correct set of extensions for that unit in the act of installing the new OS.
OS X is another matter altogether. Apple still inserts custom files into the OS disc, but these alone may not prevent it from starting, although they might cause a system crash by their presence or absence; in a Unix environment as Mac OS is, these "kernel modules" may simply be disabled. Apple being what it is, the designers may have programmed the machine's firmware so as not to accept a lower build of Mac OS.
Things get further complicated if you, say, try to use a PPC iinstaller or image of 10.4 on an Intel machine. Each machine type has specific requirements, for which two separate versions of Tiger were made. If the older server was an Xserve G4 or G5, and its data were imaged onto an Xserve Xeon, it would fail because the Xeon unit is not capable of booting volumes created with the Apple Partition Map scheme used by PowerPC Macs. Likewise, if the Xeon unit were cloned to previous models, the latter would not be able to boot from the GPT volume created on the former.
Server media can be universal, but the server itself must still be formatted in the proper partition scheme for its type.
Leopard tries to bridge this gap by making one monolithic installer, which again tries autodetection and then installs machine -specific items followed by universal items.
Recently, in yet another shocking twist, Apple may have implemented machine-level copy protection in newer restore media. The only confirmed evidence of the lock is a series of cautionary articles posted on Apple's Support Knowledgebase.
Nate
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