Figure 17-7. Upgrade Presence Detect Schematic - Case 1 - Intel Pentium Pro Family Developer's Manual

OVERDRIVE® PROCESSOR SOCKET SPECIFICATION
OverDrive processor and the OEM VRM is NOT replaced with the OverDrive VRM,
the original voltage regulator will never enable its outputs because the lower voltage
OverDrive processor could be damaged. Refer to Figure 17-7.

Figure 17-7. Upgrade Presence Detect Schematic - Case 1

— Case 2: Header 8 AND alternate voltage source
If the system is designed with alternate voltage source and a Header 8 for future
upgrade support, then the UP# signal must be connected between Socket 8, Header 8,
and the alternate voltage source. The Pentium Pro processor voltage regulator should
use the UP# signal to disable the voltage output when detected low (indicating that an
OverDrive processor has been installed). The OverDrive VRM, when installed into the
Header 8 will use the UP# signal to enable its outputs (when detected low). When the
Pentium Pro processor is replaced with an OverDrive processor and the OverDrive
VRM is installed, the original voltage regulator must never enable its outputs because
the lower voltage OverDrive processor could be damaged. Refer to Figure 17-8.
Figure 17-8. Upgrade Presence Detect Schematic - Case 2
17-12
+ 5 Volt
10 k Ω
UP#
Header 8
+ 5 Volt
10 k Ω
Header 8 UP#
On-Board VR
Socket 8
Socket 8