Datasheet, Volume 2
57
Processor Configuration Registers
2.5.12
GGC—GMCH Graphics Control Register Register
All the bits in this register are Intel TXT lockable.
B/D/F/Type:
0/0/0/PCI
Address Offset:
50–51h
Reset Value:
0028h
Access:
RW-KL, RW-L
Size:
16 bits
BIOS Optimal Default
00h
Bit
Attr
Reset
Value
RST/
PWR
Description
15:15
RO
0h
Reserved
14
RW-L
0b
Uncore
Versatile Acceleration Mode Enable (VAMEN)
Enables the use of the iGFX enable for Versatile Acceleration.
1 = iGFX engines are in Versatile Acceleration Mode. Device 2
Class Code is 048000h.
0 = iGFX engines are in iGFX Mode. Device 2 Class Code is
030000h.
13:10
RO
0h
Reserved
9:8
RW-L
0h
Uncore
GTT Graphics Memory Size (GGMS)
This field is used to select the amount of Main Memory that is pre-
allocated to support the Internal Graphics Translation Table. The
BIOS ensures that memory is pre-allocated only when Internal
graphics is enabled.
GSM is assumed to be a contiguous physical DRAM space with
DSM, and BIOS needs to allocate a contiguous memory chunk.
Hardware will derive the base of GSM from DSM only using the
GSM size programmed in the register.
Hardware functionality in case of programming this value to
Reserved is not ensured.
Encoding:
1h = 1 MB of pre-allocated memory
2h = 2 MB of pre-allocated memory
3h = Reserved
0h = No pre-allocated memory