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82801AA and 82801AB ICH Datasheet
7-9
Hub Interface-to-PCI Bridge Registers (D30:F0)
7.1.17
MEMBASE—Memory Base Register (HUB-PCI—D30:F0)
Offset Address:
Default Value:
20–21h
FFF0h
Attribute:
Size:
R/W
16 bits
This register defines the base of the hub interface to PCI non-prefetchable memory range. Since the
ICH will forward all hub interface memory accesses to PCI, the ICH will only use this information
for determining when not to accept cycles as a target.
This register must be initialized by the configuration software. For the purpose of address decode,
address bits A[19:0] are assumed to be 0. Thus, the bottom of the defined memory address range
will be aligned to a 1 MB boundary.
7.1.18
MEMLIM—Memory Limit Register (HUB-PCI—D30:F0)
Offset Address:
Default Value:
22–23h
0000h
Attribute:
Size:
R/W
16 bits
This register defines the upper limit of the hub interface to PCI non-prefetchable memory range.
Since the ICH will forward all hub interface memory accesses to PCI, the ICH will only use this
information for determining when not to accept cycles as a target.
This register must be initialized by the configuration software. For the purpose of address decode,
address bits A[19:0] are assumed to be FFFFFh. Thus, the top of the defined memory address range
will be aligned to a 1 MB boundary.
7.1.19
PREF_MEM_BASE—Prefetchable Memory Base Register
(HUB-PCI—D30:F0)
Offset Address:
Default Value:
24h–25h
0000FFF0h
Attribute:
Size:
R/W
16-bit
Bit
Description
15:4
Memory Address Base.
Defines the base of the memory range for PCI. These 12 bits correspond
to address bits 31:20.
3:0
Reserved.
Bit
Description
15:4
Memory Address Limit.
Defines the top of the memory range for PCI. These 12 bits correspond to
address bits 31:20.
3:0
Reserved.
Bit
Description
15:4
Prefetchable Memory Address Base
—
R/W.
Defines the base address of the prefetchable
memory address range for PCI. These 12 bits correspond to address bits 31:20.
3:0
Reserved. RO.