E
PENTIUM II PROCESSOR AT 233 MHZ, 266 MHZ, 300 MHZ, AND 333 MHZ
85
all Pentium II processor System Bus agents.
Observing BPRI# active (as asserted by the priority
agent) causes all other agents to stop issuing new
requests, unless such requests are part of an
ongoing locked operation. The priority agent keeps
BPRI# asserted until all of its requests are
completed, then releases the bus by deasserting
BPRI#.
A.1.13
BR0# (I/O), BR1# (I)
The BR0# and BR1# (Bus Request) pins drive the
BREQ[1:0]# signals in the system. The BREQ[1:0]#
signals are interconnected in a rotating manner to
individual processor pins. Table 30 gives the rotating
interconnect between the processor and bus signals.
Table 30. BR0# (I/O) and BR1# Signals
Rotating Interconnect
Bus Signal
Agent 0 Pins
Agent 1 Pins
BREQ0#
BR0#
BR1#
BREQ1#
BR1#
BR0#
During power-up configuration, the central agent
must assert the BR0# bus signal. All symmetric
agents sample their BR[1:0]# pins on active-to-
inactive transition of RESET#. The pin on which the
agent samples an active level determines its agent
ID. All agents then configure their pins to match the
appropriate bus signal protocol, as shown in
Table 31.
Table 31. BR[1:0]# Signal Agent IDs
Pin Sampled Active in RESET#
Agent ID
BR0#
0
BR1#
1
A.1.14
BSEL# (I/O)
The BSEL# (Bus Select) signal is used for future
Slot 1 processors and motherboards. This signal
must be tied to GND for proper processor operation.
A.1.15
D[63:0]# (I/O)
The D[63:0]# (Data) signals are the data signals.
These signals provide a 64-bit data path between the
Pentium II processor System Bus agents, and must
connect the appropriate pins on all such agents. The
data driver asserts DRDY# to indicate a valid data
transfer.
A.1.16
DBSY# (I/O)
The DBSY# (Data Bus Busy) signal is asserted by
the agent responsible for driving data on the
Pentium II processor System Bus to indicate that the
data bus is in use. The data bus is released after
DBSY# is deasserted. This signal must connect the
appropriate pins on all Pentium II processor System
Bus agents.
A.1.17
DEFER# (I)
The DEFER# signal is asserted by an agent to
indicate that a transaction cannot be guaranteed in-
order completion. Assertion of DEFER# is normally
the responsibility of the addressed memory or I/O
agent. This signal must connect the appropriate pins
of all Pentium II processor System Bus agents.
A.1.18
DEP[7:0]# (I/O)
The DEP[7:0]# (Data Bus ECC Protection) signals
provide optional ECC protection for the data bus.
They are driven by the agent responsible for driving
D[63:0]#, and must connect the appropriate pins of
all Pentium II processor System Bus agents which
use them. The DEP[7:0]# signals are enabled or
disabled for ECC protection during power on
configuration.
A.1.19
DRDY# (I/O)
The DRDY# (Data Ready) signal is asserted by the
data driver on each data transfer, indicating valid
data on the data bus. In a multi-cycle data transfer,
DRDY# may be deasserted to insert idle clocks. This
signal must connect the appropriate pins of all
Pentium II processor System Bus agents.