Intel III Xeon 900 MHz 80526KY9002M Data Sheet

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The BCLK (Bus Clock) is a 2.5V tolerant signal that determines the bus frequency. All Pentium® III Xeon™ processor at
600 MHz+  system bus agents must receive this signal to drive their outputs and latch their inputs on the BCLK rising
edge.

All external timing parameters are specified with respect to the BCLK signal.

The BERR# (Bus Error) signal is asserted to indicate an unrecoverable error without a bus protocol violation. It may be
driven by all Pentium III Xeon processor at 600 MHz+ system bus agents, and must connect the appropriate pins of all
such agents, if used. However, Pentium III Xeon processor at 600 MHz+ do not observe assertions of the BERR# signal.

BERR# assertion conditions are configurable at a system level. Assertion options are defined by the following options:

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Enabled or disabled.

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Asserted optionally for internal errors along with IERR#.

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Asserted optionally by the request initiator of a bus transaction after it observes an error.

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Asserted by any bus agent when it observes an error in a bus transaction.

The BINIT# (Bus Initialization) signal may be observed and driven by all Pentium III Xeon processor at 600 MHz+  system
bus agents, and if used must connect the appropriate pins of all such agents. If the BINIT# driver is enabled during power
on configuration, BINIT# is asserted to signal any bus condition that prevents reliable future information.

If BINIT# observation is enabled during power-on configuration, and BINIT# is sampled asserted, all bus state machines
are reset and any data which was in transit is lost. All agents reset their rotating ID for bus arbitration to the state after
reset, and internal count information is lost. The L1 and L2 caches are not affected.

If BINIT# observation is disabled during power-on configuration, a central agent may handle an assertion of BINIT# as
appropriate to the Machine Check Architecture (MCA) of the system.

The BNR# (Block Next Request) signal is used to assert a bus stall by any bus agent who is unable to accept new bus
transactions. During a bus stall, the current bus owner cannot issue any new transactions.

Since multiple agents might need to request a bus stall at the same time, BNR# is a wire-OR signal which must connect
the appropriate pins of all Pentium III Xeon processor at 600 MHz+ system bus agents. In order to avoid wire-OR glitches
associated with simultaneous edge transitions driven by multiple drivers, BNR# is activated on specific clock edges and
sampled on specific clock edges.

The BP[3:2]# (Breakpoint) signals are outputs from the processor that indicate the status of breakpoints.

The BPM[1:0]# (Breakpoint Monitor) signals are breakpoint and performance monitor signals. They are outputs from the
processor that indicate the status of breakpoints and programmable counters used for monitoring processor performance.

The BPRI# (Bus Priority Request) signal is used to arbitrate for ownership of the Pentium III Xeon processor at 600 MHz+
system bus. It must connect the appropriate pins of all Pentium III Xeon processor at  600 MHz+ 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#.