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Technote 1050 Release 1.1

JUNE 1996

This Technote describes the various changes offered by System 7.5.3 Revision 2 and provides information for Apple developers regarding these changes. This Note also includes references to other sources of information that further discuss these changes.

CONTENTS

• About System 7.5.3 Revision 2
  
• System Enabler Changes
  
• Startup Tuner INIT Changes
  
• Detecting System 7.5.3 Revision 2
  
• Changes in the "About This Macintosh" Dialog Box
  

About System 7.5.3 Revision 2

System Enabler Changes

• Type 8 errors on PowerBooks
• Cache flushing on PowerBooks
• Floppy driver on the PowerBook 5300
• Dynamic Recompiling Emulator
• Potential SCSI Problem

Type 8 Errors

Cache Flushing

Floppy Driver on the 5300

Dynamic Recompiling Emulator

A Potential SCSI Problem

With the internal fast bus on the PCI Power Macintoshes, the SCSI Manager did not "know" the device was in status phase after the reconnect because of a difference in the way the controller works. The SCSI Manager now correctly issues the RESTORE_POINTERS command. The transaction will be correctly reported as successful. This fix affects only PCI PowerMacs running Mac OS which use the 1 gigabyte IBM drive with write caching disabled. Apple ships these drives with write caching enabled. However, write caching may be disabled by some third-party SCSI utilities. This is a preventive measure rather a common occurrence.

For more details on write caching, see Technote 1040 "Write Cache Flushing: Techniques for Properly Handling System Shutdown."

Startup Tuner INIT Changes

Drive Spin Up

Other Changes

System 7.5.3 Revision 2 may require the creation of a "System 7.5.3 Enabler" on some machines which currently do not ship with such an enabler as part of System 7.5.3. If the "System 7.5.3 Enabler" is created, it will contain all of the bug fixes listed above, as well as most of the bug fixes listed in the "If System Software 7.5.3 is Present..." section of Technote 1017. If a machine already has a "System 7.5 Enabler" or "System 7.5.2 Enabler" installed, then that enabler is updated instead.

Detecting System 7.5.3 Revision 2

Figure 1: The format of the Gestalt response for the 'sysu' selector.

The presence of the 'sysu' Gestalt selector allows application programs to determine if the current installed system software version was established using the system update. The 'sysu' Gestalt selector will only be defined if a system update package was used to establish the current system version: the 'sysu' selector is not defined on machines shipped with System 7.5.3 installed.

Using the `sysv' and `sysu' Gestalt Selectors

	long response, updateversion;
	OSErr err;
	Boolean seven_five_three;
	Boolean is_an_update;
	
	seven_five_three = false;
	is_an_update = false;
	
	err = Gestalt(gestaltSystemVersion, &response);
	if (err == noErr) {
		seven_five_three = (response == 0x00000753);
		if (seven_five_three) {
			err = Gestalt('sysu', &updateversion);
			is_an_update = (err == noErr);
		}
	}
	/* at this point, seven_five_three will be true if system 7.5.3
	is the current operating system, and is_an_update will be true
	if the current system version was established by update. if
	is_an_update is true, updateversion will contain the System
	update's version number (0x02038000 for system 7.5.3 revision 2). */

Figure 2: "About This Macintosh" dialog box with System 7.5 Update 2.0

Figure 3: "About This Macintosh" dialog box with System 7.5.3 Revision 2

Further References

• Technote 1017, "System 7.5 Update 2.0; Macintosh System 7.5.3."
• Technote 1040, "Write Cache Flushing: Techniques for Properly Handling System Shutdown."

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