Intel 815 - Manual (Page 32)

Universal Socket 370 Design
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32 Intel
®
815 Chipset Platform Design Guide
4.2.2 Identifying the Processor at the Socket
For the platform to configure for the requirements of the processor in the socket, it must first
identify whether the processor is a Pentium III processor (CPUID=068xh) / Celeron processor
(CPUID=068xh), or a future 0.13 micron socket 370 processors. Pin AF36 is a ground pin on a
Pentium III processor (CPUID=068xh) and Celeron processor (CPUID=068xh); pin AF36 is an
unconnected pin on future 0.13 micron Socket 370 processors. Referring to Figure 8, the platform
uses a detect circuit connected to this processor pin. If a future 0.13 micron Socket 370 processor
is present in the socket, the TUAL5 reference schematic signal will be pulled to the 5V rail and the
TUAL5# reference schematic signal will be pulled to ground. Otherwise, for a Pentium III
processor (CPUID=068xh) or Celeron processor (CPUID=068xh), the TUAL5 reference
schematic signal will be pulled to ground and the TUAL5# will be pulled to the 5V rail.
Figure 8. Processor Detect Mechanism at Socket/TUAL5 Generation Circuit
1 K Ω
2.2 K Ω
2.2 K Ω
VTT
VCC5
VCC5
TUAL5
TUAL5#
MOSFET N
NPN
Processor Pin
AF36
Proc_Detect