Pentium® III Processor for the PGA370 Socket at 500 MHz to 866 MHz
2.5
Processor System Bus Clock and Processor Clocking
The BCLK input directly controls the operating speed of the system bus interface. All AGTL+
system bus timing parameters are specified with respect to the rising edge of the BCLK input. See
the P6 Family of Processors Hardware Developer's Manual for further details.
2.5.1
Mixing Processors of Differrent Frequencies
In two-way MP (multi-processor) systems, mixing processors of different internal clock
frequencies is not supported and has not been validated. Pentium III processors do not support a
variable multiplier ratio; therefore, adjusting the ratio setting to a common clock frequency is not
valid. However, mixing processors of the same frequency but of different steppings is supported.
Details on support for mixed steppings is provided in the Pentium® III Processor Specification
Update.
Note: Not all Pentium III processors for the PGA370 socket are validated for use in dual processor (DP)
systems. Refer to the Pentium® III Processor Specification Update to determine which processors
are DP capable.
2.6
Voltage Identification
There are four voltage identification pins on the PGA370 socket. These pins can be used to support
automatic selection of VCCCORE voltages. These pins are not signals, but are either an open circuit
or a short circuit to VSS on the processor. The combination of opens and shorts defines the voltage
required by the processor core. The VID pins are needed to cleanly support voltage specification
variations on current and future processors. VID[3:0] are defined in Table 2. A ‘1’ in this table
refers to an open pin and a ‘0’ refers to a short to ground. The voltage regulator or VRM must
supply the voltage that is requested or disable itself.
To ensure a system is ready for current and future processors, the range of values in bold in Table 2
should be supported. A smaller range will risk the ability of the system to migrate to a higher
performance processor and/or maintain compatibility with current processors.
Datasheet
17
INTEL [ INTEL ]
