82801BA Datasheet, PDF (259/498 Pages) Intel Corporation – Intel 82801BA I/O Controller Hub 2 (ICH2) and Intel 82801BAM I/O Controller Hub 2 Mobile

Hub Interface to PCI Bridge Registers (D30:F0)
8.1.24
8.1.25
BRIDGE_CNT—Bridge Control Register (HUB-PCI—D30:F0)
Offset Address: 3E–3Fh
Default Value: 0000h
Attribute:
Size:
R/W
16 bits
Bit
Description
15:8 Reserved.
7
Fast Back to Back Enable—RO. Hardwired to 0. The PCI logic will not generate fast back-to-back
cycles on the PCI bus.
6
Secondary Bus Reset—RO. hardwired to 0. The ICH2 does not follow the P2P bridge reset scheme;
Software-controlled resets are implemented in the PCI-LPC device.
5
Master Abort Mode—R/W. The ICH2 ignores this bit. However, this bit is read/write for software
compatibility. The ICH2 must handle master aborts as if this bit is reset to 0.
4 Reserved.
VGA Enable—R/W.
1 = Enable. Indicates that the VGA device is on PCI. Therefore, the PCI to hub interface decoder will
3
not accept memory cycles in the range A0000h–BFFFFh. Note that the ICH2 will never take I/O
cycles in the VGA range from PCI.
0 = No VGA device on PCI.
ISA Enable—R/W. The ICH2 ignores this bit. However, this bit is read/write for software compatibility.
2 Since the ICH2 forwards all I/O cycles that are not in the USB, AC’97, or IDE ranges to PCI, this bit
would have no effect.
SERR# Enable—R/W.
1 = Enable. If this bit is set AND bit 8 in CMD register (D30:F0 Offset 04h) is also set, the ICH2 sets
1
the SSE bit in PD_STS register (D30:F0, offset 06h, bit 14) AND also generate an NMI (or SMI#
if NMI routed to SMI) when the SERR# signal is asserted.
0 = Disable
Parity Error Response Enable—R/W.
0 1 = Enable the hub interface to PCI bridge for parity error detection and reporting on the PCI bus.
0 = Disable
BRIDGE_CNT2—Bridge Control Register 2
(HUB-PCI—D30:F0)
Offset Address: 40h
Default Value: 00h
Attribute:
Size
R/W
8 bits
Bit
Description
7:1 Reserved
PCI_DAC_EN—R/W. Allows ICH2 to recognize external PCI masters performing DAC on PCI.
0
0 = Disable.
1 = Enable.
82801BA ICH2 and 82801BAM ICH2-M Datasheet
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