FlushInstructionCache Flush the instruction cache

#include <Memory.h> Memory Manager

The FlushInstructionCache function flushes the current contents of the

instruction cache. Because flushing this cache degrades performance of the

CPU, this routine should be called only when absolutely necessary.

Notes: Be sure to check that the trap _HWPriv is implemented before calling this

routine. See Using the Gestalt Manager for sample code that shows how

to determine whether a trap is implemented. If you call this routine and

_HWPriv is not implemented, you application will crash.

The MC68020, MC68030 and MC68040 micro processors have

Any time you modify part of executable code, you risk creating stale

instructions in the instruction cache. A micro processor that contains an

instruction cache store the most recently executed instructions in its

internal instruction cache, separate from main memory. Whenever your

code modifies itself or any data in memory that contains executable code,

there is a possibility that a copy of the modified instructions will be in the

instruction cache. If so, attempting to execute the modified instructions

actually results in the execution of the cached instructions, which are stale.

Stale instructions can be avoided by flushing the instruction cache every

time you modify executable instructions in memory. Flushing the cache

invalidates all entries in it and forces the processor to refill the cache from

If you want to flush the instruction cache of a processor with a copy-back

data cache, such as the MC68040 processor, you may want to write your

own routine that calls the _CacheFlush trap in assembly language. This

trap flushes the data cache before it flushes the instruction cache to insure

that any instructions subsequently copied to the instructions cache are not

// FlushCache

// Flush the CPU cache(s). This is required on the 68040 after modifying

// code.

#define _CacheFlushTrap 0xA0BD

void FlushCache(void)

{

if (TrapAvailable( _CacheFlushTrap))

asm

{

dc.w _CacheFlushTrap

}

The preceding code example calls a routine called TrapAvailable. See

Using the Gestalt Manager for the definition of this routine.