Unfortunately, Apple's inconsistent naming scheme (calling it both System 7.5.3 and System 7.5 Update 2.0) greatly confused users. In addition, bugs in Update 2.0 forced Apple to update the update, calling it Revision 2. If this wasn't bad enough, Apple also shipped tens of thousands of machines with an interim version of System 7.5, called 7.5.2, and strongly urged these users to update to Update 2.0 as soon as possible. Some mistakenly thought 7.5.2 must already have Update 2.0 since it ended with a "2."
Finally, hundreds of thousands of other users (perhaps millions) failed to note that this was an update of System 7.5 (and 7.5.1 and 7.5.2), not the earlier System 7 or System 7.1. Update 2.0 is irrelevant to any version of MacOS prior to System 7.5.
The tables below (based on Apple documentation) attempt to offer some clarification of Apple's peculiar naming system, and (via the About This Macintosh window) clues to help you discover what you currently have installed.
If you are running System 7.5 and wish to upgrade to 7.5.3, your ultimate goal should be System 7.5.3, Revision 2. This is also the preferred environment for those working with the latest Apple technology, such as OpenDoc and Open Transport.
| Installer | Requires System Software for Installer | Updates to Version |
| System 7.5 Update 2.0 | 7.5, 7.5.1, or 7.5.2 | System 7.5.3 |
| System 7.5 Revision 2 | 7.5.3 | System 7.5.3 Rev. 2 |
| System 7.5 version 7.5.3 | Full installer | System 7.5.3 Rev. 2 |
| Installer | Requires System Software for Installer | Updates to Version |
| PB 5300 System Software Update | 7.5.2 enabler 1.1.1 or earlier | 7.5.2 enabler 1.2.1 |
| Sys. 7.5.3 Revision 2 | 7.5.2 enabler 1.2.1 | 7.5.2 enabler 1.2.4 |
| In About This Macintosh window | How To Get To This Level Of System Software |
| System 7.5 | Retail product, preinstalled on many Macintosh computers |
| System 7.5.1 | System 7.5 plus System 7.5 Update 1.0 |
| System 7.5.2 | Shipped on first PCI desktop Macintosh computers and PowerBook 190, 5300, & Duo 2300 series |
| System 7.5.3 | Shipped on some desktop Macintosh computers |
| System 7.5.3 System 7.5 Update 2.0 | Upgrading any of the above using System 7.5 Update 2.0 |
| System 7.5.3 Updated to Revision 2 | Install System 7.5.3 Revision 2 |
| System 7.5.3 Revision 2 | System 7.5 version 7.5.3 (retail package) or pre-installed on some Macintosh computers |
For more information see Apple's Technical Info Library at http://www.support.apple.com/
Important note: Apple's top management has promised never to allow such a confusing naming system out the door again. But stay tuned; a new update (7.5.4) is due before the end of 1996.
Addendum: the update was entitled 7.5.5; 7.5.4 was withdrawn. MacOS 7.6 is due in January or February 1997.