First check the memory control panel settings. If the computer supports it, make sure 32-bit addressing is on or all RAM above 8MB will get allocated to the system software. Next make sure the disk cache is not too high. Disk Cache is recommended to be set at 32K per 1024K of physical RAM or lower. Memory used by the RAM Disk is allocated to the system software. Boot with extensions off to see if an extension is using the additional RAM. Lastly, under System 7.1 and later, move the fonts folder to the desktop and reboot to see if a corrupt font is using the RAM.
The System Heap and System Software partition can hold a lot of different software components. In a situation like this, after starting the CPU with a known good System Folder or after a clean install, look for incompatible device drivers as the culprit. Device drivers can be present on any SCSI device attached to the Macintosh or on NuBus/PDS expansion cards. Test by disconnecting the SCSI chain or by removing internal cards.
Article Change History:
06 Jan 1995 - Updated discussion section.
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