Electrical Differences For Flexible Pga370 Designs - Intel 810A3 Design Manual

PGA370 Processor Design Guidelines
2.1

Electrical Differences for Flexible PGA370 Designs

®
Intel 810A3 Chipset Design Guide
This chapter provides PGA370 processor design guidelines including the PGA370
socket, Layout Guidelines, BSEL implementation, CLKREF, Undershoot/Overshoot
requirements, Reset, Decoupling guidelines, Thermal/EMI differences, and Debug Port
changes. The layout guidelines are processor-specific and should be used in conjunction
with the Chapter 4, "Layout and Routing
terminology applies:
•
Legacy PGA370 refers to today's Intel
PGA370 socket for the microprocessor. In general, these designs support 66/100
MHz host bus operation, VRM 8.2 DC-DC Converter Guidelines, and Intel
Celeron processors.
•
Flexible PGA370 refers to new generation Intel
utilizing the PGA370 socket and designed for microprocessor flexibility. In
general, these designs support 66/100 MHz bus operation for the Intel
chipset and 66/100/133 MHz host bus operation for the Intel
VRM 8.4 DC-DC Converter Guidelines and Intel
® ®
III processor PGA single processor based designs.
Intel Pentium
There are several electrical changes between the legacy and flexible PGA370 design.
They include:
•
Changes to the PGA370 socket pin definitions. Intel
utilize a superset of the Intel
•
Addition of VTT (AGTL+ termination voltage) delivery to the PGA370 socket.
•
Additional PLL reference voltage, 1.25V, on new CLKREF pin.
•
More stringent undershoot/overshoot requirements for CMOS and AGTL+ signals.
•
Addition of on-die Rtt (AGTL+ termination resistors) for the Intel
processor. Requirement remains for on-motherboard Rtt implementation if

supporting the Intel
processors, the reset signals (RESET#) still requires termination to V
motherboard.
Guidelines". For this chapter, the following
®
810A3 chipset platforms utilizing the

Celeron processor pin definition.
Celeron (PPGA). If only supporting Intel
®
810A3/810E chipset platforms
®
810A3
®
810E chipset ,
®
Celeron, and
® ®
III processors
Pentium
®
Pentium
®
Pentium
on the
TT
2
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®
III
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III
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