System Overview 1-23
Table 1-1 PCI Motherboard Slot Numbering
Slot
PCI0
PCI1
1
PCI to EISA/ISA
bridge
Internal CD-ROM
controller
2
PCI slot
PCI slot
3
PCI slot
PCI slot
4
PCI slot
PCI slot
The logic for two PCI buses is on each PCI motherboard.
•
PCI0 is a 64-bit bus with a built-in PCI to EISA/ISA bus bridge. PCI0 has three
PCI slots and one EISA/ISA slot. When the EISA/ISA slot is used, PCI slot 4
on PCI bus 1 is not available. An 8-bit XBUS is connected to the EISA/ISA
bus. On this bus there is an interface to the system I
2
C bus; mouse and keyboard
support; an I/O combo controller supporting two serial ports, the floppy
controller, and a parallel port; a real-time clock; two 1-Mbyte flash ROMs
containing system firmware, and an 8-Kbyte NVRAM.
•
PCI1 is a 64-bit bus with a built-in CD-ROM SCSI controller with three PCI
slots.
Cable connectors to the CD-ROM, the floppy, and the OCP are on the motherboard.
Connectors for the mouse, keyboard, two COM ports, the serial port, and a modem
are on the system bulkhead. The bulkhead is part of the system motherboard.
