I just found this on TidBITS. 68k references or potential references are highlighted in blue:
"The 7.5.5 Update does not contain a plethora of new features, cool gizmos, and funky icons nestled in your System folder. Instead, the update is primarily a set of under-the-hood patches, fixes, and updates to System 7.5.3, including important updates to Virtual Memory, the SCSI Manager, LocalTalk and Ethernet networking, as well as a number of fixes for specific types of Macs. In addition, System 7.5.5 includes a welcome fix to the Modern Memory Manager that eliminates one cause of the infamous "Type 11 errors" on all Power Macs.
The primary features of the 7.5.5 Update are as follows:
Improved Virtual Memory: System 7.5.5 includes significant changes to Apple's built-in Virtual Memory; the result should be improved performance when using and switching between applications or documents that require large amounts of RAM. Also, several potentially-crashing bugs were fixed, and changes that had previously been made for Virtual Memory on Power Macs were rolled into
the 68K version. Macs should boot faster using the new Virtual Memory code, and Power Macintosh applications should launch more quickly. Please note that these fixes only apply if you use Apple's built-in Virtual Memory: if you use RAM Doubler or another third-party product for virtual memory, none of this applies.
SCSI Manager: The SCSI Manager includes a number of low-level fixes to problems that could result in hangs and crashes on Power Macs.
Code Fragment Manager: Changes to the Code Fragment Manager on Power Macintoshes should allow code libraries to load better in tight memory situations, which should be useful in improving the performance of PowerPC applications and games on entry-level Performas and other systems. (There are no changes to the
68K version of the Code Fragment Manager.)
The System 7.5.5 extension set in Extensions Manager now correctly includes all QuickTime 2.5 extensions.
Better-behaved background applications: In a very welcome fix, a long-standing bug with multiple background applications and the Process Manager has been fixed on all Macintosh models - basically, the system would hang if two or more background applications made a specific, common Toolbox call (MaxApplZone). Though this problem was well-known and well-documented, it's been lurking for years and still catches developers (and users!) by surprise. Faceless background applications include things like the File Sharing extension, Microsoft OLE, and numerous helper components of other applications and utilities.
Fixes for machines which support the Infrared Remote Control, including
Macs with the Apple TV Tuner.
Correct IR Talk control panels and drivers for
all machines supporting IR Talk. System 7.5.3 Revision 2 didn't include these items, resulting in varying "clean" installations of the IR Talk software.
Improved Math routines: System 7.5.5 contains new, more efficient math routines, which might produce a slight performance improvements in some applications using these routines. However, these new math routines will also cause those applications to use 23K more memory (see below).
The System 7.5.5. Update also includes a number of machine-specific fixes:
Fixes for a hang in the 68K emulator (and File Manager) on the PowerBook 5300, 2300, and PCI-based Macintosh computers.
Ethernet fixes for 5400/6400-series computers that should improve communications on busy networks. (There's also an obscure LocalTalk fix for 5400/120s being used both as a server and a Remote Access server.)
A problem initializing the PCI bridge chip on fast (180 MHz or faster) PCI Macs has been addressed, and the systems should now start up "more reliably." Further, these machines now correctly format floppy disks (they weren't waiting long enough for the formatting to complete), and floppy disk-related hangs on NuBus-based Power Macs have been fixed.
All machine-specific fixes included in System 7.5.3 Revision 2.0 (see TidBITS-332)."
I am interested now in that central paragraph, as neither Virtual Memory nor Math Routines matter for my purposes. As I understand it, however, the "call" in question has implications for memory fragmentation in the old versions of the Macintosh operating system, so this might make it worthwhile to install the update.
Can anyone elaborate on the bug referenced? I am no programmer.
Full piece here:
http://www.nzdl.org/cgi-bin/library.cgi?e=d-00000-00---off-0tidbits--00-0----0-10-0---0---0direct-10---4-------0-1l--11-en-50---20-about---00-0-1-00-0-0-11-1-0utfZz-8-00&a=d&c=tidbits&cl=CL1.1&d=HASH011da4427147d071a5359625.5