Technical Reference Guide
Compaq Deskpro 4000 and 6000 Personal Computers
featuring the Pentium II Processor
First Edition -October 1997
5-39
5.9 ULTRA SCSI ADAPTER
The system board integrates an Ultra SCSI adapter that provides an Ultra SCSI interfaces for
compatible SCSI peripheral devices. The interfaces are provided through an Adaptec AIC-7860
controller that is backward-compatible with previous SCSI implementations.
NOTE:
[1] LED mounted on unit bezel.
Figure 5–13
. SCSI Adapter, Block Diagram
The adapter follows standard SCSI guidelines in supporting up to seven devices using SCSI
identification numbers 0-6 (ID #7 is reserved for the adapter). Each SCSI device chain must be
terminated at both ends.
NOTE:
The adapter includes two connectors; and external Ultra SCSI connector and an
internal Ultra SCSI connector. The internal connector is attached to a SCSI hard drive
in the standard configuration. A system with multiple SCSI devices must have those
devices interfacing through either the internal connector
or
the external connector,
but
not both
.
The BIOS code for the 7860 is included in the system’s BIOS ROM and is copied during POST
to the option ROM space at segment E8000h. The BIOS provides the following functions:
♦
INT 13h for multiple controllers and drives.
♦
Pass-through SCSI commands
♦
Synchronous and wide negotiations (initiated using pass-through)
♦
Fault prediction support (Compaq-supported drives only)
AIC-7860
SCSI
Controller
HD LED [1]
SCSI Connector (Ext)
SCSI
Activity
SCSI Bus
PCI Bus 0
Process
or
SCSI Connector (Int)
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