Dell Dimension XPS 50 Reference Manual page 149

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Palette Allows an ISA expansion card to check a PCI expansion card
Snooping for an updated graphics palette. If this option is set to
Disabled, the ISA expansion card may not be updated along
with the PCI expansion card.
AGP Aperture Size Sets the aperture size for the AGP video controller to 64 MB
(default) or 256 MB.
Default Primary Supports the Windows 98 and Windows 2000
Video Adapter multiple-monitor feature. Select AGP (default) to specify the
AGP video card as the primary video adapter. Select PCI to
specify a PCI video card as the primary video adapter.
NOTE: The Glossary in the system Help defines abbreviations and acronyms.
System Setup Program B-15