Host-PCI Express* Graphics Bridge Registers (D1:F0)
R
126
Intel
®
82925X/82925XE MCH Datasheet
8.1.22
BCTRL1—Bridge Control (D1:F0)
PCI Device:
1
Address Offset:
3Eh
Default Value:
0000h
Access: RO,
R/W
Size: 16
bits
This register provides extensions to the PCICMD1 register that are specific to PCI-PCI bridges.
The BCTRL provides additional control for the secondary interface (i.e., PCI Express) as well as
some bits that affect the overall behavior of the “virtual” Host-PCI Express bridge embedded
within MCH (e.g., VGA compatible address ranges mapping).
Bit Access
&
Default
Description
15:12
Reserved
11 RO
0b
Discard Timer SERR Enable:
Hardwired to 0.
10 RO
0b
Discard Timer Status:
Hardwired to 0.
9 RO
0b
Secondary Discard Timer:
Hardwired to 0.
8 RO
0b
Primary Discard Timer:
Hardwired to 0.
7 RO
0b
Fast Back-to-Back Enable (FB2BEN):
Hardwired to 0.
6 R/W
0b
Secondary Bus Reset (SRESET):
Setting this bit triggers a hot reset on the
corresponding PCI Express* Port.
5 RO
0b
Master Abort Mode (MAMODE):
When acting as a master, unclaimed reads
that experience a master abort returns all 1s and any writes that experience a
master abort completes normally and the data is thrown away. Hardwired to 0.
4 R/W
0b
VGA 16-bit Decode:
This bit 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.
3 R/W
0b
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].
Summary of Contents for 82925X
Page 78: ...Host Bridge DRAM Controller Registers D0 F0 R 78 Intel 82925X 82925XE MCH Datasheet...
Page 98: ...EPBAR Registers Egress Port Register Summary R 98 Intel 82925X 82925XE MCH Datasheet...
Page 108: ...DMIBAR Registers Direct Media Interface DMI RCRB R 108 Intel 82925X 82925XE MCH Datasheet...
Page 156: ...Host PCI Express Graphics Bridge Registers D1 F0 R 156 Intel 82925X 82925XE MCH Datasheet...
Page 172: ...System Address Map R 172 Intel 82925X 82925XE MCH Datasheet...
Page 192: ...Electrical Characteristics R 192 Intel 82925X 82925XE MCH Datasheet...