
PI7C8150B
2-PORT PCI-TO-PCI BRIDGE
ADVANCE INFORMATION
Page 87 of 115
July 31, 2003 – Revision 1.031
14.1.17
MEMORY BASE REGISTER – OFFSET 20h
Bit
3:0
Function
Type
R/O
Description
Lower four bits of register are read only and return 0.
Reset to 0
Defines the bottom address of an address range for the bridge to
determine when to forward memory transactions from one interface
to the other. The upper 12 bits correspond to address bits [31:20]
and are writable. The lower 20 bits corresponding to address bits
[19:0] are assumed to be 0.
Reset to 0
15:4
Memory Base
Address [15:4]
R/W
14.1.18
MEMORY LIMIT REGISTER – OFFSET 20h
Bit
19:16
Function
Type
R/O
Description
Lower four bits of register are read only and return 0.
Reset to 0
Defines the top address of an address range for the bridge to
determine when to forward memory transactions from one interface
to the other. The upper 12 bits correspond to address bits [31:20]
and are writable. The lower 20 bits corresponding to address bits
[19:0] are assumed to be FFFFFh.
31:20
Memory Limit
Address [31:20]
R/W
14.1.19
PEFETCHABLE MEMORY BASE REGISTER – OFFSET 24h
Bit
3:0
Function
64-bit addressing
Type
R/O
Description
Indicates 64-bit addressing
0000: 32-bit addressing
0001: 64-bit addressing
Reset to 1
Defines the bottom address of an address range for the bridge to
determine when to forward memory read and write transactions from
one interface to the other. The upper 12 bits correspond to address
bits [31:20] and are writable. The lower 20 bits are assumed to be 0.
15:4
Prefetchable
Memory Base
Address [31:20]
R/W
14.1.20
PREFETCHABLE MEMORY LIMIT REGISTER – OFFSET 24h
Bit
19:16
Function
64-bit addressing
Type
R/O
Description
Indicates 64-bit addressing
0000: 32-bit addressing
0001: 64-bit addressing
Reset to 1
Defines the top address of an address range for the bridge to
determine when to forward memory read and write transactions from
one interface to the other. The upper 12 bits correspond to address
bits [31:20] and are writable. The lower 20 bits are assumed to be
FFFFFh.
31:20
Prefetchable
Memory Limit
Address [31:20]
R/W