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APPENDIX A MIPS III INSTRUCTION SET DETAILS
Preliminary User’s Manual S15543EJ1V0UM
467
CACHE
Cache (3/4)
CACHE
Code Cache Name Operation
0 I Index_Invalidate Set the cache state of the cache block to Invalid.
0 D Index_Write_
Back_Invalidate
Examine the cache state and W bit of the primary data cache block at the index
specified by the virtual address. If the state is not Invalid and the W bit is set, then
write back the block to memory. The address to write is taken from the primary cache
tag. Set cache state of primary cache block to Invalid.
1 I, D Index_Load_Tag Read the tag for the cache block at the specified index and place it into the TagLo
CP0 registers, ignoring parity errors. Also load the data parity bits into the ECC
register.
2 I, D Index_Store_
Tag
Write the tag for the cache block at the specified index from the TagLo and TagHi
CP0 registers.
3 D Create_Dirty_
Exclusive
This operation is used to avoid loading data needlessly from memory when writing
new contents into an entire cache block. If the cache block does not contain the
specified address, and the block is dirty, write it back to the memory. In all cases, set
the cache state to Dirty.
4 I, D Hit_Invalidate If the cache block contains the specified address, mark the cache block invalid.
5 D Hit_Write_Back
Invalidate
If the cache block contains the specified address, write back the data if it is dirty, and
mark the cache block invalid.
5 I Fill Fill the primary instruction cache block from memory. If the CE bit of the Status
register is set, the contents of the ECC register is used instead of the computed parity
bits for addressed doubleword when written to the instruction cache.
6 D Hit_Write_Back If the cache block contains the specified address, and the W bit is set, write back the
data to memory and clear the W bit.
6 I Hit_Write_Back If the cache block contains the specified address, write back the data unconditionally.