The MAC Brush test version differs from the iOS device Brush Beta, iOS device if you are upgrading the beta version of what problems, it is easier to brush back to the original version (validation is not closed), but the MAC brush test version after the reload system is relatively troublesome.
Therefore, users who want to upgrade their experience of the Apple Yosemite (OS X 10.10) Beta are advised to install the beta system on a hard disk partition to avoid overwriting the original system. So even if the beta system affects the work, we can still go back to the original system. However, it is a good idea to ensure that your Mac hard disk has a total capacity of more than 256GB to consider installing Yosemite on your hard disk partition.
Install OS x10.10 system graphics and text tutorial on hard disk partitions:
First, hard disk partition preparation
1, open the Disk tool, select the partition: "Partition Layout" select "2 Partitions";
2, the second partition size adjustment, control around 50GB, the name of the proposed, the format default "Mac OS expansion (log-type)";
3, after the completion of the second step, click on the lower right corner of the "Application", waiting for the following progress bar to complete;
2, after the division of the area, the next can be installed Yosemite.
Second, download and install the Yosemite test version
1, download Yosemite (OS X 10.10) Beta;
2, the production start U disk;
3, installation: To remember is to be sure to install the Yosemite just new out of the 50GB hard drive inside, so that will not cover the original system.
At this point, your Mac has two OS X systems installed, and the new installed Yosemite is run by default at startup. If you want to go back to the original system, hold down option during the startup process until you have the option to select the Startup disk.