Specifications

CHAPTER 3
I/O Features
SCSI Bus 29
second and a data buffer that further enhances performance. Table 3-6 is a summary of
the specifications of the CD-ROM drive.
SCSI Bus 3
The Macintosh Performa 6400 computer has a SCSI bus for the internal CD-ROM device,
one additional internal SCSI device, and one or more external SCSI devices. The
CD-ROM device and any additional internal SCSI device receive power directly from the
power supply.
SCSI Connectors 3
The SCSI connector for the internal SCSI devices is a 50-pin connector with the standard
SCSI pin assignments. It attaches to a cable that is connected to the main logic board by
the internal chassis connector. The external SCSI connector is a 25-pin D-type connector
with the same pin assignments as other Apple SCSI devices. Table 3-7 shows the pin
assignments on the internal and external SCSI connectors.
Table 3-6 Specifications of the AppleCD 600i CD-ROM drive
Feature Specification
Rotation speed Approximately 920 to 2120 rpm
Average access time Less than 200 ms
Sustained transfer rate 1200 KB per second
SCSI burst rate More than 3 MB per second
Table 3-7 Pin assignments for the SCSI connectors
Pin number
(internal 50-pin)
Pin number
(external 25-pin)
Signal
name Signal description
2 8 /DB0 Bit 0 of SCSI data bus
4 21 /DB1 Bit 1 of SCSI data bus
6 22 /DB2 Bit 2 of SCSI data bus
8 10 /DB3 Bit 3 of SCSI data bus
10 23 /DB4 Bit 4 of SCSI data bus
12 11 /DB5 Bit 5 of SCSI data bus
14 12 /DB6 Bit 6 of SCSI data bus
continued