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.
B/D/F/Type:
Address Offset:
Reset Value:
Access:
0/0/0/PCI
48–4Fh
0000000000000000h
RW
64 bits
Size:
BIOS Optimal Default
0000000000h
Reset
Value
RST/
PWR
Bit
Access
Description
63:39
RO
0h
Reserved (RSVD)
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.
38:15
RW
000000h
Uncore
14:1
0
RO
0h
0b
Reserved (RSVD)
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
RW
Uncore
This register is locked by Intel TXT.
2.5.13
GGC—GMCH Graphics Control Register
All the bits in this register are Intel TXT lockable.
B/D/F/Type:
Address Offset:
Reset Value:
Access:
0/0/0/PCI
50–51h
0028h
RW-L, RW-KL
16 bits
00h
Size:
BIOS Optimal Default
Reset
Value
RST/
PWR
Bit
Access
Description
15
14
RO
RW-L
RO
0h
0b
0h
Reserved (RSVD)
Reserved (RSVD)
Reserved (RSVD)
Uncore
13:10
Datasheet, Volume 2
55
INTEL [ INTEL ]
