Author: Dave Lyons
Year: 1989
... discusses a flag byte at location $E100CB that debugging utilities can use to temporarily prevent the Memory Manager from moving or purging memory.
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.