The internal hard disk drive has a storage capacity of 20, 30, or 40 GB. The drive uses the Ultra DMA ATA interface, which is also referred to as the ATA-5 interface. The transfer rate is 66 MB per second, which is sometimes referred to as ATA-66 or UDMA Mode 4. The internal hard disk drive is connected as device 0 (master) in an ATA Device 0/1 configuration.
The software that supports the internal hard disk is the same as that in previous Macintosh models with internal ATA drives and includes DMA support. To obtain information about that software and about the ANSI standard for the Ultra DMA ATA interface, see ATA Devices.