Datasheet
Datasheet, Volume 2 55
Processor Configuration Registers
2.5.12 MCHBAR—Host Memory Mapped Register Range Base
Register
This is the base address for the Host Memory Mapped Configuration space. There is no
physical memory within this 32 KB window that can be addressed. The 32 KB reserved
by this register does not alias to any PCI 2.3 compliant memory mapped space. On
reset, the Host MMIO Memory Mapped Configuration space is disabled and must be
enabled by writing a 1 to MCHBAREN [Device 0, offset 48h, bit 0].
All the bits in this register are locked in Intel TXT mode.
The register space contains memory control, initialization, timing, and buffer strength
registers; clocking registers; and power and thermal management registers.
2.5.13 GGC—GMCH Graphics Control Register
All the bits in this register are Intel TXT lockable.
B/D/F/Type: 0/0/0/PCI
Address Offset: 48–4Fh
Reset Value: 0000000000000000h
Access: RW
Size: 64 bits
BIOS Optimal Default 0000000000h
Bit Access
Reset
Value
RST/
PWR
Description
63:39 RO 0h Reserved (RSVD)
38:15 RW 000000h Uncore
Host Memory Mapped Base Address (MCHBAR)
This field corresponds to bits 38:15 of the base address Host
Memory Mapped configuration space. BIOS will program this
register resulting in a base address for a 32 KB block of
contiguous memory address space. This register ensures that a
naturally aligned 32 KB space is allocated within the first 512 GB
of addressable memory space. System software uses this base
address to program the Host Memory Mapped register set. All the
bits in this register are locked in Intel TXT mode.
14:1 RO 0h Reserved (RSVD)
0RW 0bUncore
MCHBAR Enable (MCHBAREN)
0 = Disable. MCHBAR is disabled and does not claim any
memory
1 = Enable. MCHBAR memory mapped accesses are claimed and
decoded appropriately
This register is locked by Intel TXT.
B/D/F/Type: 0/0/0/PCI
Address Offset: 50–51h
Reset Value: 0028h
Access: RW-L, RW-KL
Size: 16 bits
BIOS Optimal Default 00h
Bit Access
Reset
Value
RST/
PWR
Description
15 RO 0h Reserved (RSVD)
14 RW-L 0b Uncore Reserved (RSVD)
13:10 RO 0h Reserved (RSVD)