3.3.1) What is the Corvus disk system?

For mass storage capacity beyond that of floppy disk drives, microcomputer
users of the time of the Atari could turn to drives that utilized a "fixed" or
"sealed" magnetic disk.  Such devices were still widely known in the early
1980s as "Winchester" disks, after the code name for IBM's influential 3340
Direct Access Storage Facility (14"; 70MB or 140MB) introduced back in 1973.
As they became much more common by the mid 1980s, the Winchester term mostly
disappeared from common usage, along with the alternatives "fixed-disk" and
"sealed disk", all ultimately replaced by today's: "hard disk drive"

One feature of early hard disk drives was that the disk controller was usually
a separate component from the disk itself.  In the late 1970s and early 1980s
several different interface standards for communications between computer
host, controller, and disk competed for market acceptance.  This complicated
market landscape, combined with the extreme costs involved, severely limited
the sales of hard disks for early home computers.

Corvus Systems teamed with disk-maker International Memories Inc. (IMI) to
develop and market complete, integrated Winchester disk systems compatible
with many computer platforms, including the Atari 800.  It was the first and
remained the only hard disk drive solution available for an Atari computer for
several years.

Corvus Systems Atari 800 Disk System (1982) includes:
   - Corvus Winchester Disk Drive unit, one of:
      - Corvus B-Series 5.25" 6MB
        (IMI 5007 disk with IMI 5000 Phase III controller)
      - Corvus B-Series 8" 11MB
        (IMI 7710 disk with embedded controller)
      - Corvus B-Series 8" 20MB
        (IMI 7720 disk with embedded controller)
      - Corvus H-Series 5.25" 6MB (Model 6)
        (IMI 5006H disk with IMI 5000H controller)
      - Corvus H-Series 5.25" 12MB (Model 11)
        (IMI 5012H disk with IMI 5000H controller)
      - Corvus H-Series 5.25" 18MB (Model 20)
        (IMI 5018H disk with IMI 5000H controller)
   - Corvus Atari Interface (host adapter)
      - Attaches to Atari 800 controller jacks 3 and 4
      - Attaches to Processor port on Corvus drive (34 pin Corvus-IMI bus)
   - Two different "AT Utilities" diskettes (v.1 and v.2)
   - Disk System Installation Guide and System Manager's Guide
- The power switch is on the front of the 8" drives, while it's on the back on
  the 5.25" drives.
- Drive units can be daisy-chained.  The Processor port of an add-on drive can
  be connected to the Drive port of an existing drive (34 pin Corvus-IMI bus).
  Up to 4 Corvus hard drives (any of the above models) can be connected to one
  computer.
- Requires 48KiB RAM, and 810 or equivalent floppy disk drive.
- SYSGEN utility divides the drive into any combination of 90KiB and 180KiB
  "volumes" for use by the Atari as logical drives.  A Model 20 drive may
  contain up to 196 single-sized volumes (with no double-sized volumes) or up
  to 98 double-sized volumes (with no single-sized volumes).
- System must boot using Corvus bootstrap from either disk or cassette.
   - WRITEBOOT.OBJ utility creates a Corvus Boot Disk out of Atari DOS 2.0S,
     which boots to: Disk Operating System II Corvus A2.0D (4/25/81)
   - CWRTBOOT.OBJ utility creates a boot cassette
- Multiple users support - each "user" can have access to up to 8 logical
  drives, which can be any combination of Corvus volumes or Atari drives
  (except logical drive 1 must be Corvus volume 1 or an Atari drive where a
  Corvus boot disk will be used).
   - Usage: User boots the system with uniquely-assigned boot disk, then uses
     the DOS L. BINARY LOAD option to load the user's unique "volume mount
     table" file, which maps the user's assigned Corvus volumes to logical
     drives.
- Optional: Corvus Mirror (internal)
   - Mirror video in and video out phono jacks connect to corresponding jacks
     on a VCR (VHS or Beta)
   - Corvus volumes or the entire Corvus drive can be backed-up or restored
     from backup.
- Sold separately by Corvus:
   - Corvus Multiplexer - Configured as a Host, unit connects to the Processor
     port of a Corvus drive and provides 8 Processor ports (34 pin Corvus-IMI
     bus) to the system, allowing up to 8 computers to be connected to the
     system.  Configured as a Master, unit allows Multiplexer Host units to be
     attached to the 8 Processor ports of the Master unit.  Thus up to 64
     computers can share the same Corvus hard drive (or set of up to 4 daisy-
     chained Corvus hard drives).
     (System upper limit: 80MB of storage shared by 64 computers)
   - Corvus Mirror (external unit) - Same as internal Mirror, but is connected
     between the Corvus drive and the Atari Interface, or between a Corvus
     drive and a Corvus Multiplexer. (34 pin Corvus-IMI bus)
- Sold separately by ?????: Right Cartridge which boots the Atari from the
  Corvus.  (source: Integrater manual.  Details????)
- Sold separately by ADS: Integrater (1983)
   - Detailed elsewhere in this FAQ List (personality boards for the 800)
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