Mac OS 7.5.3 Revision 2

Mac OS 7.5.3 Revision 2, otherwise known as System 7.5.3 Revision 2 or System 7.5.3 Updated to Revision 2, was a "rapid response update" from Apple to address bug reports after Mac OS 7.5.3 was released.

Background
In the months following the release of Mac OS 7.5.3, Apple Inc. released various minor patches and updates, insignificant enough that they did not warrant a new version number. However, the bug reports kept pouring in. Apple had to address errors on PCI-based Power Macs and PowerPC PowerBooks, and these required more significant updates.

As a response to the fragmented bug fixes targeting different hardware and software channels, Apple announced its "rapid response updates" program to streamline bug fixes through a single publishing process. This set the stage for Mac OS 7.5.3 Revision 2. (Although a Revision 1 never actually occurred, the number 2 was chosen to reflect the fact that earlier Revisions -- those that never made it to end-users -- did actually exist.)

The two-disk upgrade fixed problems on the PowerBook 5300 and PowerBook Duo 2300c, as well as any PowerBooks, with or without PowerPC chips, that ran Connectix RAM Doubler; any PowerBook 200 or 500 models which were upgraded to PowerPC status, as well as all Power Macintosh 7200, 7500, 7600, 8500 and 9500 systems.

In the About This Macintosh dialogue box, the Revision modified the name of the OS to read "System 7.5.3 Updated to Revision 2". However, on Macintosh computers that came with Revision 2 already installed, the OS was named, instead, "System 7.5.3 Revision 2". Despite the minor changes in the naming game, the two operating systems were exactly the same.

The very naming got even more confusing for people. Mac OS 7.5.3 was installed by System 7.5 Update 2.0, but this update was called System 7.5.3 Revision 2 -- they confused Update 2.0 (the base release version) and Revision 2 (the first major update to the release version).

Despite the numbering confusion, the revision finally re-established a standard system for all Macs.

Emulators

 * Infinite Macintosh (running Mac OS 7.5.3 Revision 2) by Mihai Parparita (if Safari has issues, try Chrome)