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You must use RAM Charger
8.1 or later
If you are running RAM Charger with Mac OS 8 with a
desktop picture using an older RAM Charger, then following
the launch of any application there will be a delay the
first time any portion of the desktop needs to be redrawn.
Download RAM Charger 8.1
here.
This is because during launch RAM Charger has forced the
desktop picture to be "lost" and it must be restored - which
takes time. There is potential for this to happen at any
time, with or without RAM Charger, should your memory be
fairly full. However, this will happen every time following
a launch if an older RAM Charger is enabled. This problem
happens subsequent to all application launches when RAM
Charging is installed, no matter what applications are RAM
Charged.
This problem was worked around in RAM Charger 8.1 (first
tested in 8.1b3).
Details
Desktop Pictures appears to keep a "pre-processed" copy
of the desktop picture in memory, within the "free pool of
memory" used by RAM Charger (the "free pool" is more
technically referred to as the "ProcessZone" or "TempZone").
This "pre-processed" copy of the desktop picture is
"purgable", which means that it may be discarded at any time
if the memory is required for other operations.
If the "pre-processed" copy of the desktop picture is
purged, then you will see a delay the first time the desktop
picture is required for screen update. At such a time
(called "lazy-evaluation"), the picture must be
re-processed, and thus the pause. This is directly analogous
to the sort of pauses you may occasionaly see with virtual
memory, since "purgable" memory is a specialized
implementation of virtual memory which requires no processor
support. Purgable memory is supported at a higher level, in
the memory manager and in applications.
In older versions of Mac OS, the free pool of memory was
purged each time an application was launched (by a call
MaxMem on the ProcessZone). In the past, RAM Charger has
supplemented this launch-purge by gathering adjacent
"purged" blocks into contiguous chunks. This allowed some
applications to launch that would fail to launch the first
time, but succeed when launched again since adjacent
"purged" blocks would have been gathered late in the first
launch. PrintMonitor showed this behavior under low memory
conditions.
In system 8, Mac OS must no longer purge the free pool of
memory each time an application is launched (macsbug: "atb
maxmem; tvb maxmem"). If the system did, you would see the
problem with Desktop pictures without RAM Charger. As a
result, we have removed our enhancement to the Mac OS 8
"launch-purge". Apparently, it is no longer required.
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