AC82G41SLGQ3 Datasheet, PDF (73/604 Pages) Intel Corporation – Intel® 4 Series Chipset Family

System Address Map
3.10.1
3.11
3.11.1
PCI Express* I/O Address Mapping
The (G)MCH can be programmed to direct non-memory (I/O) accesses to the PCI
Express bus interface when processor initiated I/O cycle addresses are within the PCI
Express I/O address range. This range is controlled via the I/O Base Address (IOBASE)
and I/O Limit Address (IOLIMIT) registers in (G)MCH Device 1 configuration space.
Address decoding for this range is based on the following concept. The top 4 bits of the
respective I/O Base and I/O Limit registers correspond to address bits A[15:12] of an
I/O address. For the purpose of address decoding, the (G)MCH assumes that lower 12
address bits A[11:0] of the I/O base are zero and that address bits A[11:0] of the I/O
limit address are FFFh. This forces the I/O address range alignment to 4 KB boundary
and produces a size granularity of 4 KB.
The (G)MCH positively decodes I/O accesses to PCI Express I/O address space as
defined by the following equation:
I/O_Base_Address ≤ Processor I/O Cycle Address ≤ I/O_Limit_Address
The effective size of the range is programmed by the plug-and-play configuration
software and it depends on the size of I/O space claimed by the PCI Express device.
The (G)MCH also forwards accesses to the Legacy VGA I/O ranges according to the
settings in the Device #1 configuration registers BCTRL (VGA Enable) and PCICMD1
(IOAE1), unless a second adapter (monochrome) is present on the DMI Interface/PCI
(or ISA). The presence of a second graphics adapter is determined by the MDAP
configuration bit. When MDAP is set, the (G)MCH will decode legacy monochrome I/O
ranges and forward them to the DMI Interface. The IO ranges decoded for the
monochrome adapter are 3B4h, 3B5h, 3B8h, 3B9h, 3BAh, and 3BFh.
Note that the (G)MCH Device 1 and/or Device 6 I/O address range registers defined
above are used for all I/O space allocation for any devices requiring it (such a window
on PCI Express).
The PCICMD1 register can disable the routing of I/O cycles to PCI Express.
(G)MCH Decode Rules and Cross-Bridge Address
Mapping
VGAA = 000A_0000 – 000A_FFFF
MDA = 000B_0000 – 000B_7FFF
VGAB = 000B_8000 – 000B_FFFF
MAINMEM = 0100_0000 to TOLUD
HIGHMEM = 4 GB to TOM
RECLAIMMEM = RECLAIMBASE to RECLAIMLIMIT
Legacy VGA and I/O Range Decode Rules
The legacy 128 KB VGA memory range 000A_0000h-000B_FFFFh can be mapped to
IGD (Device 2), to PCI Express (Device 1), and/or to the DMI Interface depending on
the programming of the VGA steering bits. Priority for VGA mapping is constant in that
the (G)MCH always decodes internally mapped devices first. Internal to the (G)MCH,
decode precedence is always given to IGD. The (G)MCH always positively decodes
internally mapped devices, namely the IGD and PCI-Express. Subsequent decoding of
regions mapped to PCI Express or the DMI Interface depends on the Legacy VGA
configurations bits (VGA Enable and MDAP).
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Datasheet
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