
iv
PRELIMINARY
A
2.4.13 BDNUM—Bridge Device Number Register ..........................................................................39
2.4.14 PBNUM—PCI Bus Number Register ...................................................................................39
2.4.15 PSBNUM—Subordinate Bus Number Register ...................................................................40
2.4.16 PBC—PB Configuration Register .........................................................................................40
2.4.17 DCC—Deturbo Counter Register .........................................................................................41
2.4.18 CRWC—CPU Read/Write Control Register .........................................................................41
2.4.19 PRWC—PCI Read/Write Control .........................................................................................42
2.4.20 SMME—SMRAM Enable Register .......................................................................................43
2.4.21 VBAE—Video Buffer Area Enable Register .........................................................................43
2.4.22 PAM[0:6]—Programmable Attribute MAp Register ...............................................................44
2.4.23 ERRCMD—Error Reporting Command Register .................................................................45
2.4.24 ERRSTS—Error Reporting Status Register .........................................................................45
2.4.25 MGR—Memory Gap Range Register ..................................................................................46
2.4.26 MGUA—Memory Gap Upper Address Register ...................................................................46
2.4.27 PFB—PCI Frame Buffer Register .........................................................................................47
2.4.28 HMGSA—High Memory Gap Range Start Address Register ..............................................48
2.4.29 HMGEA—High Memory Gap End Address Register ...........................................................48
2.4.30 IOSR1—I/O Space Range 1 Register (82454GX Only) .......................................................49
2.4.31 PCIRSR—PCI Reset Register .............................................................................................49
2.4.32 IOSR2—I/O Space Range 2 Register (82454GX Only) .......................................................50
2.4.33 APICR—I/O APIC Range Register ......................................................................................50
2.4.34 CONFVR—Configuration Values Driven on Reset Register ................................................51
2.4.35 CSCONFV—Captured System Configuration Values Register ............................................52
2.4.36 SMMR—SMRAM Range Register .......................................................................................53
2.4.37 HBIOSR—High BIOS Range Register .................................................................................53
2.4.38 EXERRCMD—PB Extended Error Reporting Command Register ......................................53
2.4.39 EXERRSTS—PB Extended Error Reporting Status ............................................................55
2.4.40 PBRTMR—PB Retry Timers ................................................................................................56
3.0 PB Functional Description ....................................................................................................................57
3.1 Memory and I/O Map ........................................................................................................................57
3.1.1 Memory Address Map ............................................................................................................57
3.1.2 I/O Address Map ....................................................................................................................59
3.2 Host Bus Interface ............................................................................................................................60
3.3 PCI Bus Interface ..............................................................................................................................61
3.4 Data Integrity and Error Handling .....................................................................................................62
3.4.1 Host Bus Errors ......................................................................................................................62
3.4.2 PCI Bus Errors .......................................................................................................................62
3.4.2.1 PB Master Operation on PCI ....................................................................................63
3.4.2.2 PB Target Operation on PCI .....................................................................................63
3.5 Dual PB Architectures (82454GX Only) ............................................................................................65