Sun Microelectronics
106
UltraSPARC User’s Manual
7.7.7 Invalidate (S_INV_REQ)
Invalidate request from SC to UltraSPARC. SC generates S_INV_REQs to service
a ReadToOwn (P_RDO_REQ) or WriteInvalidate (P_WRI_REQ) request from an-
other processor.
Etag transitions to I.
UltraSPARC issues its P_REPLY depending on the state of the E-Cache line and
the setting of the No Dual tag Present (NDP) bit in the S_INV_REQ.
If NDP=0, UltraSPARC replies with:
• P_SACK if the block is in the E-Cache. UltraSPARC also asserts P_SACK if the
block is not in the cache, but this is an error condition in systems that support
Dtags (NDP=0).
• P_SACKD if the block has been victimized from the E-Cache but not yet
written back.
If NDP=1, UltraSPARC replies with:
• P_SACK if the block is in the E-Cache.
• P_SACKD if the block has been victimized from the E-Cache but not yet
written back.
• P_SNACK if the block is not present in the E-Cache or the writeback buffer.
UltraSPARC responds more quickly if NDP=0; SC should assert NDP only in sys-
tems that do not support Dtags. Section 7.10, “S_REQ,” on page 111 for more tim-
ing information.
SC can buffer the P_SACKD reply and cancel the P_WRB_REQ when it appears.
UltraSPARC supports one outstanding coherent system request. SC can send its
next coherent request on the second cycle after the P_SACK{D} reply.
7.7.8 Copyback (S_CPB_REQ)
Copyback request from SC to UltraSPARC. SC generates S_CPB_REQ to service a
ReadToShare (P_RDS_REQ) or ReadToShareAlways (P_RDSA_REQ) request from
another processor.
The Etag final state is O or S.
UltraSPARC issues its P_REPLY depending on the state of the E-Cache line and
the setting of the No Dual tag Present (NDP) bit in the S_CPB_REQ.
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