Macintosh 800K external drive M0131

Popularly referred to as an external 800K floppy drive, the M0131 is an external drive for Sony 3.5" double-sided 800 Kbyte rigid disks. It was introduced at the same time as the Macintosh Plus, and contains the same Sony drive as the internal one in that computer. The drive also supports older 400K single-sided disks, and it can initialise a disk as single-sided to allow it to be used in an earlier Macintosh with a 400K internal drive. However, the drive normally requires the 128K ROMs and cannot be used with the original 128K RAM Mac, which can't load the HFS disk format. At the time hard disks were quite expensive, and an external floppy drive was a popular accessory to avoid repeated disk swapping with the single Macintosh internal floppy drive.

The drive controller automatically adjusts the rotational speed of the disk to minimise the change in recording density as the head moves from the inner to the outer radius of the disk.

160 tracks, 16 sectors per track.
Apple 6-and-2 group code recording (GCR).
Auto-eject function; no manual eject button or LED.
50 cm cable with DB-19 connector.

The external drive is powered from the Macintosh, which supplies:
+12v pins 7, 8.
+5v pin 6.
-12v pin 5.
Ground pins 1, 2, 3, 4.

The drive has no second connector to permit daisy-chaining several drives. However, the Apple Hard Disk 20 does have such a connector, so one or more hard disks and one external floppy drive can be connected to the same Macintosh. Unlike the Apple 3.5 Drive, the Macintosh 800K external drive does not work with Apple II computers.

The Macintosh 800K external drive was delivered with a yellow protective disk inserted into the drive. The disk ejected automatically on switching on the Macintosh after connecting the drive. It should be reinserted when transporting the drive.

Apple recommended placing the disk drive on the right side of the Macintosh to avoid magnetic interference from the left side of the computer. The circuitry connected to the pins inside the DB-19 connector is vulnerable to static discharge. Whenever the drive is not connected to a Macintosh the connector should be covered with an antistatic bag

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Elenco delle radio e altri apparecchi della Apple Computer; Cupertino, CA