Sun Microelectronics
137
7. UltraSPARC External Interfaces
7.16.11 ReadToOwn Dirty Victimized Block
Condition: Store miss by another processor (P2).
The transaction sequence shown in Table 7-35 is the same as in Section 7.16.8,
“Victim Writeback,” except that another processor P2 makes a ReadToOwn re-
quest for the victimized block in P1 before the Writeback transaction from P1 has
been acknowledged by System.
Table 7-35 Copyback-Invalidate Dirty Victimized Block
Processor 1 System Processor 2 Processor 3
Initial victim state:
Etag1{M}
Initial missed state:
Etag2{I}
P1 copies the victimized block into
the writeback buffer}
P_RDS_REQ to System
(DVP bit set)
Initial state:
Etag1{I}
Initial state:
Etag2{I}
Initial state:
Etag2{I}
S_RBU reply to P1
P1 reads the data
updates Etag2{I → E}
P_RDO_REQ to System for
victim block in P1.
S_CPI_REQ to P1
P1 makes another copy of the victim
block in the copyback buffer
P_SACKD reply to System
S_CRAB reply to P1
S_RBU reply to P2
P2 reads data and updates
Etag1{I → M}
P_WRB_REQ to system
S_WBCAN to P1
(as the Writeback has been
cancelled due to the earlier
CPI request from System due
to P2’s RDO request)
P1 clears writeback buffer tag
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