
4-6
BUS PROTOCOL
RESET# is asserted in T1, which is observed by all agents in T2. This signal forces all agents to
initialize their internal states and bus signals. In T3 or T4, all agents deassert their arbitration
request signals BREQ[3:0]#, BPRI# and arbitration modifier signals BNR# and LOCK#. The
symmetric agents reset the ownership state to idle and the Rotating ID to three (so that bus agent
0 has the highest symmetric priority after RESET# is deasserted).
In T9, after BIST and MP initialization, agent 1 asserts BREQ1# to arbitrate for the bus. In T10,
all agents observe active BREQ1# and inactive BREQ[0,2,3]#. During T10, all agents determine
that agent 1 is the only symmetric agent arbitrating for the bus and therefore has the highest pri-
ority. As a result, in T11, all agents update their Rotating ID to “1”, the Agent ID of the new
symmetric owner and its ownership state to busy, indicating that the bus is busy.
Starting from T10, agent 1 continually monitors BREQ[0,2,3]# to determine if it can park on the
bus. Since BREQ[0,2,3]# are observed inactive, it continues to maintain bus ownership by keep-
ing BREQ1# asserted.
In T16, agent 1 voluntarily deasserts BREQ1# to release bus ownership, which is observed by
all agents in T17. In T18 all agents update the ownership state from busy to idle. This action re-
duces the arbitration latency of a new symmetric agent to two clocks on the next arbitration
event.
Figure 4-2. Symmetric Arbitration of a Single Agent After RESET#
CLK
BREQ0#
BREQ1#
BPRI#
RESET#
BREQ2#
BREQ3#
1
2
3
4
5
6
8
9
10
11
13
14
15
16
17
{rotating id}
-
-
3
3
3
3
3
1
1
0
1
1
1
1
12
1
{ownership}
-
-
I
I
I
I
B
B
B
B
B
I
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
3
7
3
I
B
I
3
II
I
I
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
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: ......