Biostar P4VTB Manual page 60

P4VTB BIOS Setup
In this case, the PCI VGA controller should not respond to the Write, it should only snoop
the data and permit the access to be forwarded to the ISA bus. The non-VGA ISA graphic
controller can then snoop the data on the ISA bus.
you should disable this option.
Disabled(default)
Enabled
Assign IRQ For VGA
This item allows the users to choose which IRQ to assign for the VGA.
The Choices: Enabled (default), Disabled.
Assign IRQ For USB
This item allows the users to choose which IRQ to assign for the USB.
The Choices: Enabled (default), Disabled.
Unless you have the above situation,
Disables the function.
Enables the function.
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