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128 SPARC JPS1 Implementation Supplement: Fujitsu SPARC64 V • Release 1.0, 1 July 2002
M.2 Cache Coherency Protocols
The CPU uses the UPA MOESI cache-coherence protocol; these letters are acronyms
for cache line states as follows:
A subset of the MOESI protocol is used in the on-chip caches as well as the D-Tags in
the system controller.
TABLE M-4
shows the relationships between the protocols.
TABLE M-5
shows the encoding of the MOESI states in the L2 Cache.
M.3 Cache Control/Status Instructions
Several ASI instructions are defined to manipulate the caches. The following
conventions are common to all of the load and store alternate instructions defined in
this section:
MExclusive modified
O Shared modified (owned)
EExclusive clean
SShared clean
I Invalid
TABLE M-4
Relationships Between Cache Coherency Protocols
L2-Cache L1D-Cache SAT (store ownership) L1I-Cache
Invalid (I) Invalid (I) Invalid (I) Invalid (I)
Shared Clean (S)
Invalid (I) or Clean (C)
Invalid (I)
Invalid (I) or
Valid (V)
Shared Modified (O)
Exclusive Clean (E)
Exclusive Modified (M)
Invalid (I)
Exclusive Modified (M) Valid (V)
TABLE M-5
L2 Cache MOESI States
Bit 2 (Valid) Bit 1 (Exclusive) Bit 0 (Modified) State
0 ——Invalid (I)
100Shared clean (S)
110Exclusive clean (E)
1 0 1 Shared modified (O)
111Exclusive modified (M)