[X4U] 10.5 instead of 10.6

[Paul Moortgat]

That was the problem it all started with.  The new Mac Pro will not  
recognize the 10.5.1 CD from my 1 year old Mac Pro.  Not even if the  
10.6 was pulled out of the Pro.
And BTW, the new bays are longer than the old (mine) ones.  In total I  
had to upgrade (download) 1650 meg and lucky I could do it a lot at 1  
MByte/sec.

Paul Moortgat

On 11 Feb 2010, at 05:15, Scott Buntin wrote:

>
> On Feb 10, 2010, at 12:24 PM, Paul Moortgat wrote:
>
>> He didn't remember exactly where he heard it.  He assumed it was  
>> from Apple.
>> The Apple site <http://support.apple.com/kb/HT3964> doesn't mention  
>> anything about a lower OS.
>> He told me that part of the OS is stored there and will block a  
>> lower OS.
>>
>> Paul Moortgat
>
>
> Your friend is wrong. The SMC (and  in older machines, the PMU or  
> SMU) really doesn't care what you install.
>
> You can install any version of the OS that is greater than the  
> version that shipped with the machine. You can install the version  
> that shipped with the machine, but usually only with the DVD that  
> came in the box (not the retail OS DVD).
>
> If your machine shipped with 10.5.5, you can install 10.5.5 or  
> greater. You cannot install 10.5.0 (the retail 10.5, for instance)  
> and usually cannot install from a DVD that shipped with a different  
> model.
>
> When you run the installer for the "older" version of OS X, it will  
> not allow installing unless you change the install options. You must  
> either erase the drive, or do an "Archive Install".
>
> If you are trying to install 10.5 over 10.6, you should plan on  
> erasing the drive, or be *very* selective as to what data to keep -  
> Mail libraries, as well as some pref files created or modified in  
> 10.6 may not work well, if at all, in 10.5.