82830MP Datasheet, PDF (40/159 Pages) Intel Corporation – Intel 830MP Chipset: 82830MP Graphics and Memory Controller Hub (GMCH-M)

Intel® 830MP Chipset
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Figure 5. Hub Interface Type 1 Configuration Address Translation
31
1
Reserved
CONFIG_ADDRESS
Bus Number
Device Number
Function No.
Register Number
0
xx
Hub Interface Type 1
Configuration
Address Extension
cfg_hl1.vsd
15
Device Number
Function No.
Register Number
Reserved
31
Type 1
Bus Number
0
01
16
4.2.5 AGP/PCI1 Bus Configuration Mechanism
From the chipset configuration perspective, AGP/PCI1 is seen as another PCI bus interface residing on a
Secondary Bus side of the “virtual” PCI-PCI bridge referred to as the GMCH-M Host-AGP/PCI1 bridge.
On the Primary bus side, the “virtual” PCI-PCI Bridge is attached to PCI Bus #0. Therefore, the
PRIMARY BUS NUMBER register is hardwired to “0”. The “virtual” PCI-PCI bridge entity converts
Type #1 PCI Bus Configuration cycles on PCI Bus #0 into Type 0 or Type 1 configuration cycles on the
AGP/PCI1 interface. Type 1 configuration cycles on PCI Bus #0 that have a BUS NUMBER that
matches the SECONDARY BUS NUMBER of the GMCH-M’s “virtual” PCI-PCI Bridge will be
translated into Type 0 configuration cycles on the AGP/PCI1 interface. The GMCH-M will decode the
Device Number field [15:11] and assert the appropriate GAD signal as an IDSEL in accordance with the
PCI-to-PCI Bridge Type 0 configuration mechanism. For PCI-to-PCI Bridge translation one of 16
IDSELs are generated (as opposed to one of 21 for Host-to-PCI bridges).
When bit [15] = 0, bits [14:11] are decoded to assert a single AD[31:16] IDSEL. If bit [15] = 1,
AD[31:16] are 0000h. The remaining address bits will be mapped as described in the figure below. The
remaining address bits will be mapped as described in the Figure 6 below.
Figure 6. Mechanism #1 Type 0 Configuration Address to PCI Address Mapping
CONFIG_ADDRESS
31
24 23
16 15 14
11 10
87
210
1
Reserved
Bus Number
Device Number Function No.
Register Number
xx
31
24 23
IDSEL
16 15
11 10
87
210
Reserved = 0
Function No.
Register Number
00
AGP GAD[31:0] Address
AGP/PCI1 Type 0 Configuration Cycle
cfg_hl1.vsd
40
Datasheet
298338-001