
4-9
BUS PROTOCOL
4.1.4.4.
SYMMETRIC ARBITRATION WITH NO LOCK#
Figure 4-5 illustrates arbitration between two or more symmetric agents while LOCK# and
BPRI# stay inactive. Because LOCK# and BPRI# remain inactive, bus ownership is determined
based on a Rotating ID and bus ownership state. The symmetric agent that wins the bus releases
it to the other agent as soon as possible (the Pentium Pro processor limits it to one transaction,
unless the outstanding operation is locked). The symmetric agent may re-arbitrate one clock af-
ter releasing the bus. Also note that when a symmetric agent n issues a transaction to the bus,
BREQn# must stay asserted until the clock in which ADS# is asserted.
In T1, all arbitration requests BREQ[3:0]# and BPRI# are inactive. The bus is not stalled by
BNR#. The Rotating ID is 3 and bus ownership state is idle(I). Hence, the round-robin arbitra-
tion priority is 0,1,2,3.
In T2, agent 0 and agent 1 activate BREQ0# and BREQ1# respectively to arbitrate for the bus.
In T3, all agents observe inactive BREQ[3:2]# and active BREQ[1:0]#. Since the Rotating ID is
3, during T3, all agents determine that agent 0 has the highest priority and is the next symmetric
owner. In T4, all agents update the Rotating ID to zero and the bus ownership state to busy(B).
Figure 4-5. Symmetric Bus Arbitration with no LOCK#
CLK
BREQ0#
BREQ1#
BPRI#
BNR#
ADS#
BREQ2#
BREQ3#
{REQUEST}
A
A
AAAAAA
A
A
AAA
AA
A
AAAA
A
A
AAA
AA
A
AAAA
AA
A
AAAA
A
A
AAA
AA
A
AAAA
A
AA
AAA
AA
A
AAAAAA
AA
AA
AAAAAA
0a
1a
2a
1
2
3
4
5
6
7
8
9
10
11
12
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14
15
16
{rotating id}
3
3
3
0
0
1
1
1
2
0
0
0
0
0
2
0b
A
A
AAAAAA
2
{ownership}
I
I
I
B
B
B
B
B
B
B
B
B
B
B
B
B
LOCK#
Содержание Pentium Pro Family
Страница 17: ...1 Component Introduction ...
Страница 26: ...2 Pentium Pro Processor Architecture Overview ...
Страница 27: ......
Страница 36: ...3 Bus Overview ...
Страница 62: ...4 Bus Protocol ...
Страница 105: ...5 Bus Transactions and Operations ...
Страница 126: ...6 Range Registers ...
Страница 131: ...7 Cache Protocol ...
Страница 135: ...8 Data Integrity ...
Страница 148: ...9 Configuration ...
Страница 161: ...10 Pentium Pro Processor Test Access Port TAP ...
Страница 172: ...11 Electrical Specifications ...
Страница 201: ...12 GTL Interface Specification ...
Страница 229: ...13 3 3V Tolerant Signal Quality Specifications ...
Страница 233: ...14 Thermal Specifications ...
Страница 239: ...15 Mechanical Specifications ...
Страница 241: ...15 2 MECHANICAL SPECIFICATIONS s Figure 15 1 Package Dimensions Bottom View ...
Страница 252: ...16 Tools ...
Страница 260: ...16 8 TOOLS Figure 16 4 Generic MP System Layout for Debug Port Connection ...
Страница 264: ...17 OverDrive Processor Socket Specification ...
Страница 290: ...A Signals Reference ...
Страница 320: ...Index ...
Страница 328: ......