LV Intel
®
Pentium
®
III Processor 512K Dual Processor Platform
30
Design Guide
5.0
Power
The intent of this section is to familiarize the reader with the processor power requirements for a
LV Intel Pentium
III
processor 512K platform, and to show simulation model and power
implementation techniques. Only specific power distribution and control issues pertaining to the
LV Intel Pentium
III
processor 512K are discussed in this section. It is assumed that the reader is
familiar with power distribution issues of the Intel
®
Pentium
®
III
processors.
5.1
Terminology
“Power-Good” or “PWRGOOD” (an active high signal) indicates that all of the supplies and
clocks within the system are stable. PWRGOOD should go active at a predetermined time after
system voltages are stable and should go inactive as soon as any of these voltages fail their
specifications.
“VCC” or “Vcc
CORE
” refers to the LV Intel Pentium
III
processor 512K core’s V
CC
and cache
supply voltage.
“V
TT
” refers to the processor’s I/O supply voltage.
“AGTL” refers to the processor’s Assisted Gunning Transceiver Logic supply voltage. “AGTL” is
the bus between the processor and its chipset. The terms “AGTL” and “system bus” are
synonymous.
“VRM 8.5” refers to the voltage regulator for the LV Intel Pentium
III
processor 512K. It is a
DC-DC converter that supplies the required voltage and current to each processor.
“PLL1” and “PLL2” are voltage supplies for the processor’s PLL. These supplies must be filtered
to provide a very clean voltage source.
5.2
Typical Power Delivery
Power distribution is generally thought of as supplying power to the components that require it.
Digital designers typically assume that an ideal supply will be provided. The printed circuit board
(PCB) designers attempt to create this ideal supply with two power planes in the PCB or by using
large width traces to distribute power. High frequency noise created when logic gates switch is
typically controlled with high frequency ceramic capacitors, which are recharged from lower
frequency bulk capacitors. Various rule of thumb methods exist for determining the amount of each
type of capacitance that is required. For LV Intel Pentium
III
processor 512K dual processor
designs, the system designer needs to design beyond the rule of thumb and architect a power
distribution system that meets LV Intel Pentium
III
processor 512K specifications. Figure 16 shows
the ideal power model.
