Macintosh Hard Disk 20


At A Glance

The Macintosh Hard Disk 20 was the first hard drive produced by Apple. It was specifically for use with the Macintosh 512K and Macintosh Plus and was the first in a line of subsequent external storage products to support the Macintosh line of computers. Read the original specifications of the Macintosh Hard Disk 20 at the Apple support site.

Remember the Macintosh Hard Disk 20?

   View Results

(Voting is completely anonymous)

Loading ... Loading ...

Original Specifications


  • Storage Characteristics
    • Data Capacity: 20,769,280 bytes (formatted)
    • Data surfaces: 4
    • Heads per surface: 1
    • Total blocks: 39,040
  • Drive Characteristics:
    • Average Seek Time: 85 milliseconds
    • Head-to-disk transfer rate: 7.5 million bps
    • Rotational Speed: 2744 RPM
    • Average Startup Time: 15 seconds
    • Average Spin-down Time: 25 seconds
  • Power Requirements:
    • Line voltage: 85 to 270 volts AC, RMS
    • Frequency: 47 to 64 Hz
    • Power: 30 watts
    • Maximum Motor Start: 900 milliamps +5 volts DC


  • Interface:
    • Transfer Rate: Transfer Rate: 500 Kilobits per second (serial)
    • Expansion port: DB-19 connector
  • Environmental requirements:
    • Operating temperature: 50 to 104 F (10 to 40 C)
    • Relative Humidity: 20% to 80% condensing
    • Maximum altitude: -1000 to 10,000 feet
  • Size and weight:
    • Height: 3.1 inches
    • Width: 9.7 inches
    • Depth: 10.5 inches
    • Weight: 7 lbs. (3.2 kg)



Problem with these specifications? Let us know.

Got some suggestions / related sites we haven’t come across? Tell us about them.
[jwplayer config=”Shrine Player 1″ width=”800″ height=”448″ mediaid=”3688″]
Copyright © 2011 SOAWeb LLC - All Rights Reserved.
Shrine Of Apple is not affiliated with, endorsed by or connected to Apple Inc.