Vcmos Reference; Figure 18. Gtl_Ref/Vcmos_Ref Voltage Divider Network - Intel 815EG Design Manual

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4.2.7

VCMOS Reference

In previous platforms supporting the Pentium III processor (CPUID=068xh) and Celeron processor
(CPUID=068xh), VCMOS was generated by the same power plane as VTT. The future
0.13 micron socket 370 processors do not generate VCMOS, and the universal platform is
required to generate this separately on the motherboard. Processor pin AK22, which is a
GTL_REF pin on a Pentium III processor (CPUID=068xh) and Celeron processor
(CPUID=068xh), has been changed to a VCMOS_REF pin on future 0.13 micron socket 370
processors. Referring to Figure 18, a network of resistors and a capacitor must be added so that
this pin operates appropriately for whichever processor is in the socket.

Figure 18. GTL_REF/VCMOS_REF Voltage Divider Network

®
Intel 815EG Chipset Platform Design Guide
VCMO S
75 Ω
1%
150 Ω
.1
1%
GTL_CMOS_Ref_815E_B0
Universal Socket 370 Design
Processor Pin
AK22
µ
F
43