System 7.5.5 includes all of the improvements found in the System 7.5.3 Revision 2 update that was released in June, as well as a number of other reliability improvements. To help ease confusion, Apple has adhered to its revised system software nomenclature--changes in the first number reflect major architectural changes, changes in the second digit reflect significant additions to the OS, and the third digit reflect incremental updates.
According to Apple, performance and reliability enhancements include:
--a revised virtual memory manager that speeds application launches;
--a revised Code Fragment Manager that helps some large, PowerPC-native applications launch faster and enables some applications to launch in low memory situations;
--a reduction of "Type 11" errors on PowerPC systems, typically seen in low memory conditions;
--improved floppy formatting and reliability, and resolution of some compatibility issues involving the 5400 and 6400 series of Macs.
"What it means for Mac users is increased system stability. You'll see a little bit better performance and fixes for some compatibility problems with a few specific models," says Pieter Hartsook, editor of The Hartsook Letter, a Mac industry newsletter.
Details about the next significant update are still shifting, according to Hartsook. The Harmony release, which is now going to be called 7.6, may include appearance changes, including a customizable desktop and the updated desktop design originally slated for the Copland release. Recently, there has been talk that those changes may not be included, Hartsook said.