Processor Configuration Registers
2.6.24
BCTRL—Bridge Control Register
This register provides extensions to the PCICMD register that are specific to PCI-PCI
bridges. The BCTRL provides additional control for the secondary interface (that is, PCI
Express-G) as well as some bits that affect the overall behavior of the "virtual" Host-
PCI Express bridge embedded within the processor; such as VGA compatible address
ranges mapping.
B/D/F/Type:
Address Offset:
Reset Value:
Access:
0/1/0–2/PCI
3E–3Fh
0000h
RO, RW
16 bits
0h
Size:
BIOS Optimal Default
Reset
Value
RST/
PWR
Bit
15:12
11
Access
RO
Description
0h
0b
Reserved (RSVD)
Discard Timer SERR# Enable (DTSERRE)
Not Applicable or Implemented. Hardwired to 0.
RO
Uncore
Uncore
Uncore
Uncore
Uncore
Discard Timer Status (DTSTS)
Not Applicable or Implemented. Hardwired to 0.
10
9
RO
RO
RO
RO
0b
0b
0b
0b
Secondary Discard Timer (SDT)
Not Applicable or Implemented. Hardwired to 0.
Primary Discard Timer (PDT)
Not Applicable or Implemented. Hardwired to 0.
8
Fast Back-to-Back Enable (FB2BEN)
Not Applicable or Implemented. Hardwired to 0.
7
Secondary Bus Reset (SRESET)
Setting this bit triggers a hot reset on the corresponding PCI
Express Port. This will force the LTSSM to transition to the Hot
Reset state (using Recovery) from L0, L0s, or L1 states.
6
5
RW
RO
0b
0b
Uncore
Uncore
Master Abort Mode (MAMODE)
Does not apply to PCI Express. Hardwired to 0.
VGA 16-bit Decode (VGA16D)
Enables the PCI-to-PCI bridge to provide 16-bit decoding of VGA
I/O address precluding the decoding of alias addresses every
1 KB. This bit only has meaning if bit 3 (VGA Enable) of this
register is also set to 1, enabling VGA I/O decoding and
forwarding by the bridge.
0 = Execute 10-bit address decodes on VGA I/O accesses.
1 = Execute 16-bit address decodes on VGA I/O accesses.
4
3
RW
RW
0b
0b
Uncore
Uncore
VGA Enable (VGAEN)
This bit controls the routing of processor initiated transactions
targeting VGA compatible I/O and memory address ranges. See
the VGAEN/MDAP table in Device 0, offset 97h[0].
Datasheet, Volume 2
103
INTEL [ INTEL ]
