I install Logic on a lot of Macs. Sometimes it takes ~2 hours. Sometimes ~8 hours. Today I am installing Logic simultaneously on 2 exactly identical new iMacs with the exact OS (10.64) etc.... I start the installs at the same time. Same set of install criteria (default). Different serial numbers of course. The first disc takes 90 minutes on iMac#1 and 30 minutes on iMac#2. Each subsequent disc takes way longer on iMac#1 compared to iMac#2. In fact, 3 hours later iMac#1 is only on the 3rd disc but iMac#2 is done all 8 discs. Previously I thought the difference in time was because other stuff was different (different computer, optical drive, OS, speed etc...). But now it seems arbitrary. What is the thing that causes there to be a difference in install time?