Intel XScale Core Developer's Manual page 88

Intel XScale® Core Developer's Manual
Configuration
Other items to note about the line-allocate command are:
•
It forces all pending memory operations to complete.
•
Bits [31:5] of Rd is used to specific the virtual address of the line to allocated into the data
cache.
•
If the targeted cache line is already resident, this command has no effect.
•
This command cannot be used to allocate a line in the mini Data Cache.
•
The newly allocated line is not marked as "dirty" so it will never get evicted. However, if a
valid store is made to that line it will be marked as "dirty" and will get written back to external
memory if another line is allocated to the same cache location. This eviction will produce
unpredictable results.
To avoid this situation, the line-allocate operation should only be used if one of the following
can be guaranteed:
— The virtual address associated with this command is not one that will be generated during
normal program execution. This is the case when line-allocate is used to clean/invalidate
the entire cache.
— The line-allocate operation is used only on a cache region destined to be locked. When the
region is unlocked, it must be invalidated before making another data access.
88 January, 2004 Developer's Manual