LV Intel
®
Pentium
®
III Processor 512K Dual Processor Platform
Design Guide
31
Figure 17 shows the recommended system baseboard solution involving local voltage regulators. It
is recommended that board designers follow the guidelines in VRM 8.5 DC-DC Converter Design
Guidelines (order number 249659).
Each regulator circuit should be placed as close as possible to the corresponding processor and
aligned to the side of the socket with the higher density of power and ground pins.
Important: In previous generation Pentium
®
III
processor dual-processor systems, it was possible to source the
combined voltage and current requirements for both processors from one large voltage regulator.
However, due to the load-line characteristics specified for the LV Intel
®
Pentium
®
III
Processor 512K, Intel recommends that separate power planes be utilized. This configuration
of voltage regulators is shown in Figure 17.
To completely model the motherboard system, the designer must include the inductance and
resistance that exists in the cables, connectors, PCB planes, pins and body of components (such as
resistors and capacitors), processor and voltage regulator. A more detailed model showing these
effects is shown in Figure 18.
Figure 16. Ideal LV Intel
®
Pentium
®
III Processor 512K Power Supply Scheme
Processor
Figure 17. Power Distribution for a DP System Motherboard
Power
Supply
Voltage Regulator 1
Voltage Regulator 2
Processor 1
Processor 2