Mac OS 7.5.3 Revision 2, otherwise known as System 7.5.3 Revision 2, was a "rapid response update" from Apple to address bug reports after Mac OS 7.5.3 was released. After Mac OS 7.5.3 was released, Apple Inc. released -- in the months following the 7.5.3 release -- a few minor patches and updates, the sheer insignificance of which did not warrant any of them a version number. However, the bug reports soon came pouring in. Apple had to address errors on PCI-based Power Macs and PowerPC PowerBooks, and thse necessitated larger updates.