Service manual

System Overview 1-31
Table 1–1 PCI Motherboard Slot Numbering
Slot PCI0 PCI1
PCI2
(4000 only)
PCI3
(4000 only)
0 Reserved Reserved Reserved Reserved
1 PCI to EISA
bridge
Internal CD-ROM
controller
Reserved Reserved
2 PCI or EISA slot PCI slot PCI slot PCI slot
3 PCI or EISA slot PCI slot PCI slot PCI slot
4 PCI or EISA slot PCI slot PCI slot PCI slot
5 PCI slot PCI slot 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 bus bridge. PCI0 has one
dedicated PCI slot and three slots, though there are six connectors, that can be
PCI or EISA slots. Each slot has an EISA connector and a PCI connector only
one of which may be used at a time. PCI0 is powered by 5V.
• PCI1 is a 64-bit bus with a built-in CD-ROM controller and four PCI slots.
PCI1 is powered by 5V.
• PCI2 (4000 only) is a 64-bit four-slot PCI bus powered by both 3V and 5V.
• PCI3 (4000 only) is a 64-bit four-slot PCI bus powered by both 3V and 5V.
The B3050-AA PCI motherboard has cable connections to remote I/O (mouse,
keyboard, serial port, and parallel port), an internal floppy drive, an internal CD-
ROM drive, the control panel, and 5V power. Also on this module are the chips for
the PCI to EISA bridge and the internal CD-ROM controller. This module is the
motherboard for the PCI card cage on the left side of the system drawer.
An 8-bit XBUS is connected to the EISA 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.
The B3050-AB PCI motherboard, used only in the AlphaServer 4000, contains two
four-slot 64-bit PCI buses.