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Inside Macintosh: Memory /

Chapter 3 - Virtual Memory Manager / Virtual Memory Manager Reference

Routines / Virtual Memory Management

LockMemory

To make a portion of the address space immovable in physical memory and ineligible for paging, use the LockMemory function.

FUNCTION LockMemory (address: UNIV Ptr; count: LongInt): OSErr;

address

The starting address of the range of memory to be locked in RAM.

count

The size, in bytes, of the range of memory to be locked in RAM.

DESCRIPTION

The LockMemory function makes the portion of the address space beginning at address and having a size of count bytes immovable in physical memory and ineligible for paging.

If the address parameter supplied to the LockMemory function is not on a page boundary, it is rounded down to the nearest page boundary. Similarly, if the specified range does not end on a page boundary, the count parameter is rounded up so that the entire range of memory is locked.

The CPU marks locked pages as noncacheable. On Macintosh computers containing the Macintosh IIci ROM, all physical RAM is marked noncacheable.

ASSEMBLY-LANGUAGE INFORMATION

The trap macro and routine selector for the LockMemory function are

Trap macro	Selector
_MemoryDispatch	$0002

The registers on entry and exit for this routine are

Registers on entry
D0	Selector code
A0	Starting address
A1	Number of bytes to lock

Registers on exit
D0	Result code

RESULT CODES

noErr	0	No error
paramErr	-50	Error in parameter list
notEnoughMemoryErr	-620	Insufficient physical memory
interruptsMaskedErr	-624	Called with interrupts masked