4-12
BUS PROTOCOL
In Figure 4-7, before T1, agent 0 owns the bus. The Rotating ID is zero, the ownership state is
busy.
In T3, the priority agent asserts BPRI# to request bus ownership. In T4, agent 0, the current own-
er, issues its last request 0a. In T4, all symmetric agents observe BPRI# active, and guarantee no
new unlocked request generation starting in T5.
In T3, the priority agent observes inactive ADS# and inactive LOCK# and determines that it may
not gain request bus ownership in T5 because the current request bus owner might issue one last
request in T4. In T5, the priority agent observes inactive LOCK# and determines that it owns the
bus and may begin issuing requests starting in T7, four clocks from BPRI# assertion and three
clocks from previous request generation.
The priority agent issues two requests, I/Oa, and I/Ob, and continues to assert BPRI# through
T10. In T10, the priority agent deasserts BPRI# to release bus ownership back to the symmetric
agents. In T10, agent 1 asserts BREQ1# to arbitrate for the bus.
In T11, agent 0, the current symmetric owner observes inactive BPRI# and initiates request 0b
in T13 (three clocks from previous request.) In response to active BREQ1#, agent 0 deasserts
BREQ0# in T13 to release symmetric ownership. In T14 all symmetric agents observe inactive
BREQ0#, the release of ownership by the current symmetric owner. Since BREQ1# is the only
active bus request they assign agent 1 as the next symmetric owner. In T15 symmetric agents
update the Rotating ID to one the Agent ID of the new symmetric owner.
Figure 4-7. Bus Exchange Among Symmetric and Priority Agent with no LOCK#
CLK
BREQ0#
BREQ1#
BPRI#
LOCK#
ADS#
BREQ2#
BREQ3#
{REQUEST}
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Summary of Contents for Pentium Pro Family
Page 17: ...1 Component Introduction ...
Page 26: ...2 Pentium Pro Processor Architecture Overview ...
Page 27: ......
Page 36: ...3 Bus Overview ...
Page 62: ...4 Bus Protocol ...
Page 105: ...5 Bus Transactions and Operations ...
Page 126: ...6 Range Registers ...
Page 131: ...7 Cache Protocol ...
Page 135: ...8 Data Integrity ...
Page 148: ...9 Configuration ...
Page 161: ...10 Pentium Pro Processor Test Access Port TAP ...
Page 172: ...11 Electrical Specifications ...
Page 201: ...12 GTL Interface Specification ...
Page 229: ...13 3 3V Tolerant Signal Quality Specifications ...
Page 233: ...14 Thermal Specifications ...
Page 239: ...15 Mechanical Specifications ...
Page 241: ...15 2 MECHANICAL SPECIFICATIONS s Figure 15 1 Package Dimensions Bottom View ...
Page 252: ...16 Tools ...
Page 260: ...16 8 TOOLS Figure 16 4 Generic MP System Layout for Debug Port Connection ...
Page 264: ...17 OverDrive Processor Socket Specification ...
Page 290: ...A Signals Reference ...
Page 320: ...Index ...
Page 328: ......