Mac OS 7.5.3 Revision 2.1

With the introduction of the Performa 6400, the unity that existed with Mac OS 7.5.3 Revision 2 was shattered once again. Apple was obliged to release Mac OS 7.5.3 Revision 2.1, also known as System 7.5.3 Revision 2.1.

The Performa 6400 required a new version of LocalTalk DMA, and the video driver necessitated a fix to correct an error involving a 15-inch monitor when the Mac was going to sleep.

Only the 180 MHz and 200 MHz models of the Performa 6400 was affected. No other Macintosh had to install this revision.

This was originally going to be the final Revision of Mac OS 7.5.3; however, Mac OS 7.5.3 Revision 2.2 would appear before a fully revised, fully unified Mac OS took centre stage again.