1.4 Installation Structure

Section 4.4 of this specification defines the Plug and Play installation check procedure and structure. This mechanism defines a structure which may be located on any 16-byte boundary within the System BIOS address space of 0F0000h - 0FFFFFh. Software which must determine if it is operating on a platform supporting a Plug and Play BIOS, should scan the specified address space searching for the ASCII string "$PnP" on 16-byte boundaries. If the software identifies such a string on a 16-byte boundary, it must validate that it has indeed found a Plug and Play Installation Check Structure by verifying the structure's checksum and validate either the version field or the length field or both. A valid checksum indicates that the system BIOS provides all of the required functions of the Plug and Play System BIOS specification.

Specifying this structure in this manner permits it to float anywhere in the specified address range. This permits the System BIOS developer to locate the structure within their ROM without having to be concerned about it interfering with other structures that they may have specified at fixed addresses.