Hard Disk 20SC


At A Glance

The Apple Hard Disk 20SC, 40SC and 80SC allowed Macintosh, Apple IIe, or Apple IIGS owners to boost their disk storage capacity with a choice of 20, 40 or 80 megabyte external hard disks.

Read the original specifications of the Apple Hard Disk 20SC at the Apple Support site.

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Original Specifications


  • Recording media:
    • Two double-sided rigid fixed disks with two dual read/write heads
  • Capacity:
    • Data capacity: 20 megabytes (formatted)
    • Data surfaces: 4
    • Heads/surfaces: 1
    • Block size: 512
    • Total disk blocks: 39,360
    • Sectors/Tracks: 32
  • Characteristics:
    • Average seek time: 85 milliseconds
    • Transfer rate (Macintosh Plus): 265,000 bytes per second
    • Transfer rate (Macintosh SE): 660,000 bytes per second
    • Transfer rate (Macintosh II): 937,000 bytes per second
    • Rotational speed: 2,744 rpm
    • Startup time: 15 seconds
    • Spin-down time: 25 seconds


  • Interface:
    • Connects directly to the Macintosh Plus, Macintosh SE or Macintosh II via the external SCSI DB-25 connector
    • Connects to the Apple IIe or Apple IIGS via the expansion port, using the Apple II SCSI Interface Card
  • Electrical requirements:
    • Line voltage: 85 to 270 volts AC
    • Frequency: 47 to 64 Hz
    • Maximum power: 30 watts
  • Environmental requirements:
    • Operating temperature: 50° to 104° F (10° to 40° C)
    • Storage temperature: 32° to 122° F (0° to 50° C)
    • Relative humidity: 20% to 80% noncondensing
    • Altitude: 0 to 10,000 ft. (0 to 3,048 m)
  • Size and weight:
    • Height: 3.1 inches (78.5 mm)
    • Width: 9.7 inches (246 mm)
    • Depth: 10.5 inches (266 mm)
    • Weight: 9 lbs. (4 kg)


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apple.com

For the original specifications at the Apple support web site, click here.

Wikipedia

For the Wikipedia entry on the Apple Hard Disk 20SC click here.

Herb's Collectibles

Want to buy one? Check some old ones out at Herb’s Collectibles.
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