Apple II
Technical Notes
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                                                  Developer Technical Support


Apple IIGS
#57:    Preventing Memory Compacting and Purging

Written by:    Dave Lyons                                           July 1989

This Technical Note discusses a flag byte at location $E100CB that debugging 
utilities can use to temporarily prevent the Memory Manager from moving or 
purging memory.
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If the byte at location $E100CB is non-zero, the Memory Manager will not move 
any memory blocks, and it will not purge any blocks while trying to allocate 
memory (PurgeHandle and PurgeAll will still purge blocks).

Debugging utilities may temporarily increment this byte to allocate memory in 
situations when it is not safe for existing memory blocks to be moved or 
purged.

This flag byte is for use only by debugging aids and System Software.  It 
would be mind-numbingly stupid for an application to use this flag instead of 
using HLock and HUnlock, since the advantages of a Memory Manager architecture 
with relocatable blocks would be lost.