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1-30 AlphaServer 4000/4100 Service Manual

1.15 PCI I/O Subsystem

The I/O subsystem is PCI. Both the 4100 and the 4000 have two four-slot PCI

buses that hold up to eight I/O options. One of these buses can be both PCI and

EISA but can hold not more than four options three of which may be EISA. The

4000 can have an additional two four-slot PCI buses allowing a total of sixteen

I/O options.

Figure 1-19 PCI Block Diagram

EISA:

3 32-

bit slots

I2C Bus

Interface

Mouse/

Keyboard

Combo I/O:

serial ports

parallel port

floppy cntrl

Realtime

Clock

Flash

ROM

2MB

NVRAM

8Kx8

BDATA

Xceivers

XBUS

Xceivers

XBUS

EISA

Data

Bus

PCI-0

PCI-2

PCI-1

PCI-3

4 64-bit slots

464-bitslots

4 64-bit slots

Serial

Interrupt

Logic

3.3MHz

Osc

Clock Bfr

40MHz

Clock

PCI-1 Bus

PCI-2 Bus

Serial

Interrupt

Logic

PCI to EISA Bridge

Chipset

SCSI Control

53C810

Connector

PKW0431R-96

4000 only