Apple II
Technical Notes
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                                                  Developer Technical Support


Apple IIGS
#55:    Avoiding ClrHeartBeat

Written by:    Matt Deatherage                                      July 1989

This Technical Note lists changes to the description for ClrHeartBeat.  This 
information supersedes the description in the Apple IIGS Toolbox Reference 
Manual.
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The Apple IIGS Toolbox Reference Manual gives the following cautionary note in 
the description for the call ClrHeartBeat:

    "A desk accessory may have installed tasks in the Heartbeat 
    Interrupt Task queue.  If you make a ClrHeartBeat call, you will 
    remove those tasks.  Therefore, under normal circumstances you 
    should not make this call."

This isn't rude enough to get the point across to some people, so we'll try 
again:

The Heartbeat Interrupt Task queue does not belong to the application.  
Different portions of System Software can, and will, install Heartbeat Tasks.  
If these tasks are removed, anything from a system crash to media corruption 
may result.  Nothing but System Software should make this call.


Further Reference
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    o    Apple IIGS Toolbox Reference Manual