Intel 815 - Manual (Page 29)

Universal Socket 370 Design
R
Intel
®
815 Chipset Platform Design Guide 29
4 Universal Socket 370 Design
4.1 Universal Socket 370 Definitions
The universal socket 370 platform supports Pentium III processor (CPUID=068xh) and Celeron
processor (CPUID=068xh) as well as future 0.13 micron socket 370 processors. The Pentium III
processor (CPUID=068xh) and Celeron processor (CPUID=068xh) have different requirements
for functioning properly in a platform than the future 0.13 micron socket 370 processors. It is
necessary to understand these differences and how they affect the design of the platform. Refer to
Table 1 through Table 4 for a high-level description of the differences that require additional
circuitry on the motherboard. Specific details on implementing this circuitry are discussed further
in this chapter. For a detailed description of the differences between the Pentium III processor
(CPUID=068xh) / Celeron processor (CPUID=068xh), and future 0.13 micron socket 370
processor pins, refer to Section 5.4.
Table 1. Processor Considerations for Universal Socket 370 Design
Signal
Name or
Pin
Number
Function In
Intel ® Pentium ®
III Processor
(CPUID=068xh)
and Intel
®
Celeron™
Processor
(CPUID=068xh)
Function In
Future
0.13 Micron
Socket 370
Processors
Implementation for
Universal Socket 370 Design
AF36 VSS No connect Addition of circuitry that generates a
processor identification signal used to
configure board-level operation.
AG1 VSS VTT Addition of FET switch to ground or VTT,
controlled by processor identification signal.
Note: FET must have no more than 100
milliohms resistance between source
and drain.
AJ3 VSS RESET Addition of stuffing option for pull-down to
ground, which lets designer prevent future
0.13 micron socket 370 processors from
being used with incompatible stepping of
Intel
® 82815 GMCH.
AK22 GTL_REF VCMOS_REF Addition of resistor-divider network to provide
1.0V, which will satisfy voltage tolerance
requirements of the Intel
® Pentium ® III
processor (CPUID=068xh) and Intel ®
Celeron™ processor (CPUID=068xh) as well
as future 0.13 micron socket 370 processors.
PICCLK Requires 2.5V Requires 2.0V Addition of FET switch to provide proper
voltage, controlled by processor identification
signal.