by Geoff Duncan <email@example.com>
Last week, Apple released a patch to System 7.5.3, called System 7.5.3 Revision 2 and code named Buster. Unlike the mammoth System 7.5 Update 2.0 (which shipped on some 14 floppy disks, contained major updates to the system architectures and introduced new technologies like Open Transport 1.1), System 7.5.3 Revision 2 contains only a small number of improvements for a specific range of machines. See TidBITS-318 and TidBITS-325 for more information about System 7.5.3.
Who's Affected -- Apple stresses that the update is intended only for users of the following Macintoshes:
Power Computing hasn't finished evaluating System 7.5.3 Revision 2 and does not currently have a recommendation for its customers. However, I think it's likely that owners of PowerCurve, PowerWave, PowerCenter, and PowerTower models will want to install the patch, due to the architectural similarities between those machines and models Apple is recommending for the update. I don't know if the patch should be installed on DayStar or UMAX clones; however, it's likely that earlier clones from Radius are exempt.
The System 7.5.3 Revision 2 installer does not have a Remove feature, so (as always!) back up your data before installing. Also, though the update ships on two floppy disk images, that's purely to accommodate different installations of System 7.5.3 - many users will never be prompted for the second disk. Unfortunately, I don't know whether you can successfully use System 7.5.3 Revision 2 with non-U.S. versions of System 7.5.3.
What's Fixed -- The most notable fixes in System 7.5.3 Revision 2 involve PowerBooks. First and foremost, PowerBooks running versions of RAM Doubler prior to 1.6.2 now wake up properly - formerly, these machines would fail to wake up from sleep mode unless MacsBug was installed (see TidBITS-325). The update also fixes problems associated with using and formatting PC disks in PowerBook 500 and Duo 200-series PowerBooks with PowerPC upgrades. These disks should now be readable on DOS and Windows computers. Overall performance on PowerBooks with PowerPC upgrade cards should also be improved.
In addition, a rare problem with PCI Power Macs failing to start up from the drive selected in the Startup Disk control panel has been fixed.
Finally, the most subtle change in the update (which Apple vaguely characterizes as "improved reliability") involves the Dynamic Recompiling (DR) 68K emulator used in recent Mac models. The emulator is highly reliable, but the update fixes a problem that happened in an obscure set of circumstances and sometimes caused data corruption. Because the problem occurred so rarely and at such a low level, it's impossible to point to any specific symptoms it might have caused; however, because the 68K emulator is used so extensively, it's better to have the problem resolved than lurking in the shadows.
Acquiring the Update -- You can download System 7.5.3 Revision 2 from the usual Apple servers, as well as from most online services and a few third-party sites.
The update includes two floppy disk images; to use them, you'll need a version of DiskCopy or (better) ShrinkWrap.
If you use an AppleVision monitor on your Macintosh, you must install the AppleVision Fix 1.0 for 7.5.3 before installing System 7.5.3 Revision 2.0.
Needless to say, you must have System 7.5.3 installed before you can install the update. System 7.5 Update 2.0 (which updates any version of System 7.5 to 7.5.3) is available online from Apple for free; however, Apple is now charging for CD-ROM or floppy disks versions of the update to System 7.5.3.
Who's Not Affected, What's Not Fixed -- Do you need this update? I suggest that you follow Apple's advice and install the update only on the Macs recommended by Apple. Though many power users insist on having the latest version of the system software no matter what, the fixes in this patch are so specific that there's unlikely to be any benefit to users of other machines. So, if you use a 68000-based desktop Macintosh, a 5000 or 6000-series Performa or LC, or other model not mentioned by Apple, you can forego this update.
However, as notable as the fixes in System 7.5.3 Revision 2 are, it's interesting to note what's not included. Owners of 5200, 5300, 6200, and 6300-series Performas and LCs are still waiting for Open Transport, and there's still little information available from Apple on the reported hardware handshaking problems with the serial ports in those machines.