Specifications

CHAPTER 3
I/O Features
30 Sound
SCSI Bus Termination 3
The internal end of the SCSI bus is terminated by an active terminator. The terminator is
located on the main logic board near the portion of the internal chassis connector that
contains the signals for the internal CD-ROM drive. On enclosures with only one
internal SCSI device located close to the logic board, the active termination is
automatically enabled. On enclosures with multiple SCSI devices, the active termination
is disabled, and a positive terminator is located at the end of the internal bus.
Sound 3
The sound system supports both 8-bit and 16-bit stereo sound output and input. SRS
(sound retrieval system) enhanced sound output can be optionally turned on and off
through the Sound panel of the Monitors and Sound control panel. No additional
software API is available for controlling the SRS sound enhancement.
Like other Macintosh computers, the Macintosh Performa 6400 computer can create
sounds digitally and play the sounds through the internal speakers or send the sound
signals out through the sound output jacks. The Macintosh Performa 6400 computer also
16 13 /DB7 Bit 7 of SCSI data bus
18 20 /DBP Parity bit of SCSI data bus
25 – n.c. Not connected
26 25 TPWR +5 V terminator power
32 17 /ATN Attention
36 6 /BSY Bus busy
38 5 /ACK Handshake acknowledge
40 4 /RST Bus reset
42 2 /MSG Message phase
44 19 /SEL Select
46 15 /C/D Control or data
48 1 /REQ Handshake request
50 3 /I/O Input or output
20, 22, 24, 28,
30, 34, and all
odd pins
except pin 25
7, 9, 14, 16, 18,
and 24
GND Ground
Table 3-7 Pin assignments for the SCSI connectors (continued)
Pin number
(internal 50-pin)
Pin number
(external 25-pin)
Signal
name Signal description