Bitfields for PCI Configuration Base Address: Bit(s) Description ) 0 address type (0 = memory space, 1 = I/O space) ---memory address--- 2-1 address type 00 anywhere in first 4GB 01 below 1MB 10 anywhere in 64-bit address space 11 reserved 3 prefetchable 31-4 bits 31-4 of base memory address if addressable in first 1MB or 4GB 63-4 bits 63-4 of base memory address if addressable in 64-bit memory (bits 63-32 are stored in the following base address DWORD) ---I/O address--- 1 reserved 31-2 bits 31-2 of base I/O port SeeAlso: #00878,#00902