C.1. Plug and Play Boot Devices
The type of cards required before boot are: a display device, an input device, any device that has expansion ROM, and an initial program load device(s). Plug and Play ISA cards that are needed during the boot process must power up active. Plug and Play configuration may be implemented in system BIOS or in an operating system environment. In systems where Plug and Play configuration is implemented in the system BIOS, the BIOS takes the responsibility of configuring all Plug and Play cards needed for booting the system. The default configuration may be over-ridden to have a conflict-free configuration. In systems where Plug and Play configuration does not take place until after an OS is loaded, Plug and Play devices required before boot should provide a secondary mechanism such as jumpers, switches or configuration EEPROM (preferred), that will allow a user to set a power-up configuration. This will provide the same functionality available today for users to configure the ISA bus and boot their system. The method used to set these configuration options is up to the card designer and beyond the scope of this document.
The default resource usage of a card is always reflected in the card's configuration registers. This information will allow the Plug and Play configuration or a driver to easily determine the default settings of a Plug and Play boot device regardless of the operating system the device driver was written for. The resource use of the boot devices may be over-ridden by the operating system dependent Plug and Play configuration with full co-operation of the device driver. This functionality coupled with the fact that non-boot Plug and Play devices do not power up active will lower the amount of user intervention necessary to configure a system as well as increase the chance the system will boot.
Some devices will always be boot devices. For this class of device, except for disable, no user selectable options need to be included on the card to control booting.
There is another class of device, such as a network interface card, that may be a boot device in some situations and not a boot device in others. For this type of device, a user selectable option should be included on the card that will allow the user to select the device to be active at boot time or not. Whether this is a switch, a jumper or an EEPROM setting and how this setting is selected is up to the card designer and beyond the scope of this document.