Technical Q&As

ME 04 - Determining the Size of the Disk Cache (3-July-96)

Q How do I determine the size of the Disk Cache set from the Memory Control Panel?

A The disk cache is currently (System 7) stored in the SysParmType record, which you can retrieve with the GetSysPPtr() call (documented in Inside Macintosh:Operating Systems Utilities, chapter 7). The misc field contains the size of the disk cache in 32K chunks stored in bits 8-15.

You can access this information using code such as:

#include <OSUtils.h>
short GetDiskCacheSize(void)
{
SysPPtr pramPtr;
short   diskCacheSize;

pramPtr = GetSysPPtr();

diskCacheSize = ( ((unsigned short)(pramPtr->misc)) >> 8 ) << 5; 
// diskCacheSize is now the size in K of the disk cache

return(diskCacheSize);
}

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