Intel® 865G/865GV Chipset Datasheet - download.intel.nl - Intel

Register Description3.7.11 MMADR—Memory-Mapped Range Address Register(Device 2)Address Offset:Default Value:Access:Size:14−17h00000000hR/W, RO32 bitsThis register requests allocation for the IGD registers and instruction ports. The allocation is for512 KB and the base address is defined by bits [31:19].BitDescription31:19 Memory Base Address⎯R/W. Set by the OS, these bits correspond to address signals [31:19].18:4 Address Mask⎯RO. Hardwired to 0s to indicate 512-KB address range.3 Prefetchable Memory⎯RO. Hardwired to 0 to prevent prefetching.2:1 Memory Type⎯RO. Hardwired to 00 to indicate 32-bit address.0 Memory / IO Space⎯RO. Hardwired to 0 to indicate memory space.3.7.12 IOBAR—I/O Decode Register (Device 2)Address Offset:Default Value:Access:Size:18−1Bh00000001hR/W, RO32 bitsThis register provides the base offset of the I/O registers within Device 2. Bits 15:3 areprogrammable allowing the I/O base to be located anywhere in 16-bit I/O address space. Bits 2:1are fixed and return 0s; bit 0 is hardwired to 1 indicating that 8 bytes of I/O space are decoded.Access to the 8 bytes of I/O space is allowed in power management (PM) state D0 when the I/OEnable bit (PCICMD2 bit 0) is set. Access is disallowed in PM states D1–D3 if:• the I/O Enable bit is 0• Device 2 is turned off• Internal graphics is disabled thru the fuse mechanisms.Note that access to the IOBAR register is independent of VGA functionality in Device 2. Also,note that this mechanism is available only through function 0 of Device 2.If accesses to the IOBAR is allowed, the GMCH claims all 8-, 16- or 32-bit I/O cycles from theprocessor that falls within the 8 bytes claimed.BitDescription31:16 Reserved. Read as 0.15:3I/O Base Address—R/W. This field is set by the OS. These bits correspond to address signals15:3. They provide the 16-bit I/O base address for the I/O registers.2:1 Memory Type⎯RO. Hardwired to 00 to indicate 32-bit address.0 I/O Space⎯RO. Hardwired to 1 to indicate I/O space.Intel ® 82865G/82865GV GMCH Datasheet 107