Intel
82801BA ICH2 Datasheet
8-11
Hub Interface to PCI Bridge Registers (D30:F0)
8.1.24
BRIDGE_CNT—Bridge Control Register (HUB-PCI—D30:F0)
Offset Address:
Default Value:
3E–3Fh
0000h
Attribute:
Size:
R/W
16 bits
8.1.25
BRIDGE_CNT2—Bridge Control Register 2
(HUB-PCI—D30:F0)
Offset Address:
Default Value:
40h
00h
Attribute:
Size
R/W
8 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.
3
VGA Enable
—R/W.
1 = Enable. Indicates that the VGA device is on PCI. Therefore, the PCI to hub interface decoder will
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.
2
ISA Enable—
R/W.
The ICH2 ignores this bit. However, this bit is read/write for software compatibility.
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.
1
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
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
0
Parity Error Response Enable—
R/W.
1 = Enable the hub interface to PCI bridge for parity error detection and reporting on the PCI bus.
0 = Disable
Bit
Description
7:1
Reserved
0
PCI_DAC_EN—
R/W. Allows ICH2 to recognize external PCI masters performing DAC on PCI.
0 = Disable.
1 = Enable.
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