Dell XPS 8500 (Early 2012) - Manual (Page 129)

Clearing CMOS Passwords
WARNING: Before working inside your computer, read the safety information
that shipped with your computer and follow the steps in "Before You Begin" on
page 13. For additional safety best practices information, see the Regulatory
Compliance Homepage at dell.com/regulatory_compliance.
WARNING: The computer must be disconnected from the electrical outlet to
clear the CMOS setting.
1 Remove the computer cover. See "Computer Cover" on page 23.
2 Locate the 3-pin CMOS reset jumper (
RTCRST ) on the system board. See
"System-Board Components" on page 21.
3 Remove the 2-pin jumper plug from pins 2 and 3 and fix it on pins 1 and 2.
CMOS:
System Setup Utility 129