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CHAPTER 2
Hardware Modifications
200 MB Hard Disk Drive
13
Table 2-4 lists and describes the interface signals for the 8-pin segment of the connector.
The internal hard disk is assigned a SCSI ID number (0–7). Pins 5-7 on the SCSI connector
are encoded and allow the CPU to select the appropriate device. Table 2-5 shows how the
ID signals are encoded.
Terminator 2
The hard disk has 1000-ohm termination resistors for all I/O signal lines. The lines are
pulled up to through the resistors to termination power.
Table 2-4
Hard disk SCSI connector signal assignments: SCSI ID
Pin Signal name Description
1, 2, 3, 4, 8 Unused These pins are not used and are not connected
electrically to the CPU
5 /ID1 SCSI ID 1
6 /ID2 SCSI ID 2
7 /ID4 SCSI ID 4
Table 2-5
SCSI ID encoding
ID1: Pin 5 ID2: Pin 6 ID4: Pin 7 SCSI ID
High High High 0
Low High High 1
High Low High 2
Low Low High 3
High High Low 4
Low High Low 5
High Low Low 6
Low Low Low 7