Apple Performa 6400/180 - Manual (Page 33)

Basics Intelligent Device Electronics (IDE) Hard Drive - 31
Intelligent Device Electronics (IDE)
Hard Drive
The internal hard drive uses IDE technology, commonly used
in DOS-compatible systems, and the standard ATA-2 or IDE
interface. The hard drive has a standard 40-pin ATA
connector, and a separate 4-pin power connector.
The IDE hard drive functions the same as a typical SCSI hard
drive. You must replace IDE drives like for like. The IDE
drive does not affect SCSI ID selections or SCSI termination
schemes. Six external SCSI devices may be daisy-chained
through the external SCSI port.