Datasheet

Pentium
®
III Xeon™ Processor at 500 and 550 MHz
12
Datasheet
provide termination for each Pentium
III
Xeon processor. These specifications assume the
equivalent of 6 AGTL+ loads and termination resistors to ensure the proper timings on rising and
falling edges. See test conditions described with each specification.
Due to the existence of termination on each of up to 4 processors in a Pentium
III
Xeon processor
system, the AGTL+ bus is typically not a daisy chain topology as in previous P6 family processor
systems. Also new to Pentium
III
Xeon processors, timing specifications are defined to points
internal to the processor packaging.
Analog signal simulation of the system bus is required
when
developing Pentium
III
Xeon processor based systems to ensure proper operation over all
conditions.
Pentium
®
III
Xeon™ Processor I/O Buffer Models
are available for simulation.
The
100 MHz 2-Way SMP Pentium
®
III
Xeon™ Processor/Intel
®
440GX AGPset AGTL+ Layout
Guidelines
and
Pentium
®
III
Xeon™ Processor/Intel
®
450NX PCIset AGTL+ Layout Guidelines
contain information on possible layout topologies and other information for analog simulation.
2.2 Power and Ground Pins
The operating voltage of the processor core and of the L2 cache die differ from each other. There
are two groups of power inputs on the Pentium
III
Xeon processor package to support this voltage
difference between the components in the package. There are also five pins defined on the package
for core voltage identification (VID_CORE), and five pins defined on the package for L2 cache
voltage identification (VID_L2). These pins specify the voltage required by the processor core and
L2 cache respectively. These have been added to cleanly support voltage specification variations on
current and future Pentium
III
Xeon processors.
For signal integrity improvement and clean power distribution within the S.E.C. package, Pentium
III
Xeon processors have 67 V
CC
(power) and 56 V
SS
(ground) inputs. The 67 V
CC
pins are further
divided to provide the different voltage levels to the components. V
CC
CORE
inputs for the processor
core account for 35 of the V
CC
pins, while 8 V
TT
inputs (1.5 V) are used to provide an AGTL+
termination voltage to the processor and 20 V
CC
L2
inputs are for use by the L2 cache. One
V
CC
SMB
US
pin is provided for use by the SMBus and one V
CC
TAP
for the test access port.
V
CC
SMB
US
, V
CC
L2
, and V
CC
CORE
must remain electrically separated from each other. On the
circuit board, all V
CC
CORE
pins must be connected to a voltage island and all V
CC
L2
pins must be
connected to a separate voltage island (an island is a portion of a power plane that has been divided,
or an entire plane). Similarly, all V
SS
pins must be connected to a system ground plane.
2.3 Decoupling Guidelines
Due to the large number of transistors and high internal clock speeds, the processor is capable of
generating large average current swings between low and full power states. This causes voltages on
power planes to sag below their nominal values if bulk decoupling is not adequate. Care must be
taken in the board design to ensure that the voltage provided to the processor remains within the
specifications listed in Table 5. Failure to do so can result in timing violations or a reduced lifetime
of the component.
2.3.1 Pentium
®
III Xeon™ Processor V
CC
CORE
Regulator solutions must provide bulk capacitance with a low Effective Series Resistance (ESR)
and the system designer must also control the interconnect resistance from the regulator (or VRM
pins) to the SC330 connector. Simulation is required. Bulk decoupling for the large current swings