Host-PCI Express* Bridge Registers (D1:F0)
(Intel® 82915G/82915P/82915PL Only)
R
8.1.12
IOBASE1—I/O Base Address (D1:F0)
PCI Device:
Address Offset:
Default Value:
Access:
1
1Ch
F0h
RO
8 bits
Size:
This register controls the processor-to-PCI Express Graphics I/O access routing based on the
following formula:
IO_BASE ≤ address ≤ IO_LIMIT
Only the upper 4 bits are programmable. For the purpose of address decode, address bits A[11:0]
are treated as 0. Thus, the bottom of the defined I/O address range will be aligned to a 4-KB
boundary.
Bit
Access &
Default
Description
7:4
R/W
Fh
I/O Address Base (IOBASE): This field corresponds to A[15:12] of the I/O
addresses passed by bridge 1 to PCI Express*-G. BIOS must not set this register
to 00h; otherwise, 0CF8h/0CFCh accesses will be forwarded to the PCI Express
hierarchy associated with this device.
3:0
Reserved
8.1.13
IOLIMIT1—I/O Limit Address (D1:F0)
PCI Device:
Address Offset:
Default Value:
Access:
1
1Dh
00h
R/W
8 bits
Size:
This register controls the processor-to-PCI Express Graphics I/O access routing based on the
following formula:
IO_BASE ≤ address ≤ IO_LIMIT
Only the upper 4 bits are programmable. For the purposes of address decode, address bits A[11:0]
are assumed to be FFFh. Thus, the top of the defined I/O address range will be at the top of a 4-
KB aligned address block.
Bit
Access &
Default
Description
7:4
R/W
0h
I/O Address Limit (IOLIMIT): This field corresponds to A[15:12] of the I/O
address limit of device 1. Devices between this upper limit and IOBASE1 will be
passed to the PCI Express* hierarchy associated with this device.
3:0
Reserved
Datasheet
135
INTEL [ INTEL ]
