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A-18
SIGNALS REFERENCE
A.1.41. PWR_GD (I)
PWR_GD is driven to the Pentium Pro processor by the system to indicate that the clocks and
power supplies are within their specification.
This signal is used within the Pentium Pro processor to protect circuits against voltage sequenc-
ing issues. While the MTBF of a Pentium Pro processor is on the same order as previous pro-
cessors without the use of the PWR_GD pin, the use of this signal further increases the Mean
Time Between Failures (MTBF) of the Pentium Pro processor component.
This signal will not affect FRC operation.
A.1.42. REQ[4:0]# (I/O)
The REQ[4:0]# signals are the Request Command signals. They are asserted by the current bus
owner in both clocks of the Request Phase. In the first clock, the REQa[4:0]# signals define the
transaction type to a level of detail that is sufficient to begin a snoop request. In the second clock,
REQb[4:0]# signals carry additional information to define the complete transaction type.
REQb[4:2]# is reserved. REQb[1:0]# signals transmit LEN[1:0]# (the data transfer length infor-
mation). In both clocks, REQ[4:0]# and ADS# are protected by parity RP#.
All receiving agents observe the REQ[4:0]# signals to determine the transaction type and par-
ticipate in the transaction as necessary, as shown in Table A-9.
Table A-9. Transaction Types Defined by REQa#/REQb# Signals
Transaction
REQa[4:0]# REQb[4:0]#
4
3
2
1
0
4
3
2
1
0
Deferred Reply
0
0
0
0
0
x
x
x
x
x
Rsvd
(Ignore)
0
0
0
0
1
x
x
x
x
x
Interrupt Acknowledge
0
1
0
0
0
DSZ#
x
0
0
Special Transactions
0
1
0
0
0
DSZ#
x
0
1
Rsvd
(Central agent
response)
0
1
0
0
0
DSZ#
x
1
x
Branch Trace Message
0
1
0
0
1
DSZ#
x
0
0
Rsvd
(Central agent
response)
0
1
0
0
1
DSZ#
x
0
1
Rsvd
(Central agent
response)
0
1
0
0
1
DSZ#
x
1
x
I/O Read
1
0
0
0
0
DSZ#
x
LEN#
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: ......