3.2.1) What is the Atari 810 Disk Drive?

Portions of this section developed by Laurent Delsarte from the 810 Field
Service Manual.

The Atari 810 is a floppy disk drive that provides secondary (not directly
accessible by the computer's central processing unit) and offline (removable
from the computer) magnetic storage and retrieval of digital data, using a
standard (of its time) 5.25 inch diskette.  Diskette storage capacity is
90KiB.  The 810 Disk Drive is used with a single Atari 8-bit computer with a
minimum of 16KiB of RAM installed.  Up to four 810 disk drives may be attached
and used with an Atari computer at the same time.

The front of the 810 features a Power on/off switch, a "Power" indicator
light, and a "Disk busy" indicator light.  The rear of the unit includes two
SIO ports ("I/O Connectors"), a power input jack, and drive number selector
switches:
                     Black & White left: Drive 1
                Black right, White left: Drive 2
                    Black & White right: Drive 3
                Black left, White right: Drive 4

810 Performance Specifications
- Capacity per diskette:
    40 tracks  x  18 sectors/track  =  720 sectors/disk
    720 sectors  x  128 bytes/sector  =  92,160 bytes/disk  (90KiB)
- Average Data Transfer Rate: 6000 bit/s
- Average Latency: 100 milliseconds
- Track to Track Access Time: 5 milliseconds
- Average Access Time: 74 milliseconds
- Head Settling Time: 15 milliseconds
- Head Loading Time: 35 milliseconds
- Power-up Delay: 0.5 seconds
- Maximum Data Access Time: 236 milliseconds

810 Functional Specifications
- Disk Rotation Speed: 288 RPM (Revolutions Per Minute) +- 1%
- Recording Density: 2,938 BPI (Bits Per Inch) (maximum)
- Flux Density: 5,876 FCI (Flux Changes per Inch) (maximum)
- Track density: 48 TPI (Tracks Per Inch)
- Tracks: 40  (track 1 is the outermost; track 40 is the innermost)
- Encoding method: FM (frequency modulation / "single density")
- Drive heads: One  (accesses the disk from below)
- Media used is Atari CX8100 Blank Diskette or equivalent:
   - 5.25" micro-diskette / minidiskette / mini-disk / minifloppy diskette /
     mini-floppy diskette / floppy disk
   - Soft-sectored (disks without sector holes)
      - Hard-sectored disks, which are rare, may also be used.  The sector
        holes of hard-sectored disks would be ignored by the 810.
   - 48 TPI, either single density or double density
   - 40 tracks.
      - Avoid rare early 35 track disks (introduced in 1976 as the first 5.25"
        floppy disks); these have a noticeably smaller-length drive head
        access opening than 40 track disks (introduced in 1977).  Production
        of 35 track disks was discontinued by the end of 1980.
   - Single-sided or Double-sided
      - The 810 is a single-sided drive.  A disk is inserted into the drive
        with label side up and, from below, the drive head accesses the back
        (non-label) side disk surface via the access opening on the back side
        of the disk.
      - All disk media is actually two-sided, and all disks have a drive head
        access opening on the front (label side) disk surface as well.
        "Single-sided" disks are certified for use on only one side, while
        "double-sided" disks are certified for use on either side.
      - The reverse side of a disk (the front, label side media surface) may
        be accessed by re-inserting the disk into the 810 upside-down, label
        side down.  The 810 thus sees the reverse side of the disk as another,
        entirely different, single-sided disk.  (Rare "flippy" disks, with two
        index holes/timing holes, support this for drives that use the index
        hole/timing hole; the 810 ignores the index hole/timing hole so a
        "flippy" disk is not needed.)
   NOTES:
      - 96 TPI 80-track High Density (HD) 1200KiB 5.25" floppy diskettes,
        which are very common, can NOT be used with Atari 810 and compatible
        drives.  The media is physically different from 48 TPI diskettes.
      - 96 TPI 80-track double density / "quad density" 720KiB 5.25" floppy
        diskettes, which are rare, MAY be used with Atari 810 and compatibles.
        The media in these is actually identical to that of 48 TPI diskettes.
- Diskette write enable notch status is respected: will not write to diskette
  side lacking (or having a covered) write enable notch corresponding to that
  side of the disk.
- On the Atari, an empty floppy disk drive is powered on prior to inserting a
  diskette into the drive.  Conversely, the diskette is removed from the drive
  before the drive is turned off.  These procedures protect the integrity of
  data on diskettes.

810 Internals
- 6507 MPU (MOS Technology MCS6507 or equivalent) @ 500KHz, C010745
- ROM, C011299
- 6810 128 x 8 bit static RAM (1KiB) (Motorola MCM6810), C014328
- 6532 PIA (MOS Technology 6532 RAM-I/O-Timer (RIOT) or equivalent), C010750
- Western Digital FD1771 Floppy Disk Controller (FDC) @ 1MHz, C014329
- Read/Write Head Gap: .013 inches
- Guard Band: .008 inches
- Pad Pressure: 17 grams

810 industrial design (case): Roy Nishi and Russ Farnell

The 810 underwent several significant design revisions over the course of its
manufacture.

Original 810 Disk Drive (1980-1981, no Data Separator and "Pre-Analog")
specifications:
- Micro Peripherals, Inc. (MPI) minifloppy diskette drive mechanism
- Two printed circuit boards: a Side Board and a Rear Board
- Power Input: 9 volts AC, 1.7 amperes
- Power Usage: 20-21 watts
- Power: Used with an external 9 volt AC transformer power supply:
  Atari CA014748 or equivalent (earlier 20W C014319 units only; later 18.5W
  C014319 units are inadequate)

810 drives manufactured after September 1, 1981 ("DS" sticker) shipped with an
External Data Separator Board, which improves the drive's ability to
distinguish between data pulses and clock pulses on the disk, lowering the
chance of a misread.  It is installed in the Side Board where the FDC chip
would otherwise be installed. (810 FSM p.1-9)  The Side Board stepper motor
circuit voltage was increased to regulated 12 volts DC as well, leading to
greater power requirements for the drive:
  - Power Input: 9 volts AC, 3 amperes
  - Power Usage: 30 watts
  - Power: Used with an external 9 volt AC transformer power supply:
    Atari C016804 or equivalent
The External Data Separator Board was also offered as an upgrade for earlier
810 drives.  Earlier Side Boards must be upgraded in order to accept the Data
Separator.

Next, Atari introduced the 810 Revision C ROM in November 1981 ("C" sticker).
According to Antic (Oct. 82), "ROM C causes diskettes to be formatted with an
improved sector layout which is more efficient than that used by earlier 810
control ROMs."  Performance was reported to be 20% faster than with the
original B ROM.  The ROM C was also offered as an upgrade for older drives.

810 drives produced from February 1982 used the new "810 Analog"
("810M Analog") design, further improving reliability:  (see 810 FSM p.8B-1)
  1. A Power Supply Board now bolts onto the common base plate where the Rear
     Board used to be.  The Power Supply Board contains:
      a) A redesigned Power Supply.
      b) A Tachometer/Speed Switch I.C. (frequency to voltage converter)
         added as the Tach circuit to stabilize the motor speed. 
  2. An Analog Board now bolts to the top of the Drive Mechanism.  This board
     contains the Analog circuitry which used to be on the Rear Board.  The
     major changes are to the Read/Write circuitry.  The Analog Board
     contains:
      a) Operational amplifiers ("op-amps") and discrete transistors in place
         of transistor arrays.
      b) A multiplexor chip for switching the Read/Write amplifiers.
  3. A 10 pin flat cable connects the Analog Board to the Power Supply Board.
810 Analog power: Used with an external 9 volt AC transformer power supply
  rated for at least 30 watts; shipped with Atari CA017964.
The 3 new 810 Analog components were also offered together as an upgrade:
  - CB101128 "Grass Valley Analog Board Set" for Pre-Analog 810 drives.

In November 1982, the drive mechanism of the 810 Analog disk drive was changed
from MPI to Tandon.  The Tandon version is known as the "810T Analog" disk
drive.
           TANDON (810T Analog)                 MPI (Pre-Analog & 810M Analog)
FRONT      Operated by a front latch.           Operated by a door release
BEZEL      No diskette eject mechanism.  Raise  button.
           the front latch to access diskette.  Contains a diskette eject
           Plastic guides and front latch       mechanism.
           inhibitor position the diskette.

UPPER      Contains no pressure spring.         Contains pressure spring
ARM                                             assembly.
ASSEMBLY   Adjust by turning the two nuts which Adjust pressure spring.
           secure the upper arm to the
           carriage.

STEPPER    Adjust by turning the cam screw at   Adjust by loosening setscrew
MOTOR      rear of Drive Mechanism.             to move Stepper Band Pulley.
ADJUSTMENT

TRACK 00   Adjust by monitoring increase and    Adjust for 0.010 clearance.
STOP       decrease in waveform amplitude.

WRITE      Microswitch Assembly                 Phototransistor
PROTECT
CIRCUIT

810 manuals by Atari:
- Atari 810 Disk Drive Operator's Manual C014760 (CO14760) (earlier units)
- Atari 810 Disk Drive Owner's Guide C060056 (CO60056) (later units)
- Atari 810 Disk Drive Field Service Manual
    - Preliminary (~190 pages)
    - FS015854 Rev. 1 July 1980 (~138p)
    - FD100003
       - July 1982 [Rev. 02]
       - Rev. 03 May,1983

From winter 1980 to fall 1981 the 810 shipped with CX8101 Master Diskette
(boxed; DOS I).  From fall 1981 to May 1983 the 810 shipped with CX8104 Master
Diskette II (boxed; DOS II version 2.0S or DOS 2.0S).  Box contents for both
are detailed elsewhere in this FAQ list.

810 accessories from Atari:
CX8100 5 Diskettes.  Box contains five CX8100 Atari 810 Blank Diskettes
CX8202 5 Blank Diskettes.  Box contains five CX8202 Atari 810/815 Blank
       Diskettes (certified for double density use).
       Minimal production, see: http://www.myatari.com/ebay/815dt.html
CX8111 Atari 810 Formatted Diskettes II (5 per box; retail box never shipped)

Third-party upgrades for the 810:

Fast-Chip, by Binary Corporation, 1982
- Disks formatted by an 810 with Fast-Chip utilize an improved sector
   layout which is more efficient than those created by standard 810 drives.
- 30% faster formatting for earlier 810 drives (prior to "ROM C"), or
   10% faster formatting for 810 drives with "ROM C" (Nov. 1981 or later)

Happy 810 Enhancement, by Happy Computing (Richard Adams), 1982
- Company name became Happy Computers, Inc. in 1983
- Three versions: HE810S-X for early 810 drives (no Data Separator)
                    - Upgrade includes a data separator
                   HE810S-L for pre-Analog 810 drives with Data Separator
                   HE810S-H for 810 Analog drives
- RAM buffer: 1 track / 2304 bytes / 18 sectors
- "Happy" Warp Speed standard high speed "Reads disks up to 3 times faster
   than standard 810" with any software; supporting software also supports
   buffered fast write with verify
- Navigate/edit/create nonstandard format disks
- 1982-1983 units shipped with Happy Backup Program (single drive) disk,
   including standard 810 ROM emulator and diagnostic program
- Software sold separately, 1982-1983:
   - Multiple Drive Happy Backup Program
   - Happy Compactor Program
- Warp Speed Software disk included (1983- ), contains Warp Speed DOS
   (modified Atari DOS 2.0S), Diagnostic, Sector Copier, Happy Backup, Happy
   Compactor, Multi Drive Happy Backup, Tracer
- Software sold separately, 1982- :
   - Happy Customizer Program (create non-standard disks track-by-track)
- 810 Version 7 Upgrade, hardware upgrade by Happy Computers, required for
   1982-1985 units to run Happy Warp Speed Software Rev 7, as well as other
   software sold separately by Happy Computers:
   - Warp Speed DOS XL, including under cartridge, under ROM and Axlon RAM
     versions (modified DOS XL by Optimized Systems Software (OSS))
   - TOP DOS version 1.5, by Eclipse Software
- Software sold separately:
   - Happy Version Archiver/Editor, by Spartan Software of Minnesota, 1984
      - Also marketed by B&C ComputerVisions as: Scan-It!/810 Happy, 1987
   - Fuzzy/Phantom Sector Maker, by CSS, 1986 (Antic 9/86p48)
   - Archiver Enhancement, by Computer Software Services (CSS), 1987
      - Super Archiver/Editor 3.0, The Archiver Tracer

The Chip, by Spartan Software of Minnesota, 1983-1984
The Chip with Archiver I, by ICD, 1984
Scan-It!/Chip, from B&C ComputerVisions, 1987
- Popularly: "Archiver chip", "810 Archiver", "Archiver/810", "Archiver"
- Navigate/edit/create nonstandard format disks
- Shipped with Archiver/Editor program
    - Disassembler, sector editor, custom formatter and mapper
- Software sold separately:
   - Archiver Enhancement, by Computer Software Services (CSS), 1987
      - Super Archiver/Editor 3.0, The Archiver Tracer

Right-Write, by Gardner Computing, 1983
- Write to side 2 of any disk without notching out a hole in the disk
DS-810 Disk-Switch, by Computer Software Center (CSC), 1983
- Write to side 2 of any disk without notching out a hole in the disk
- Write protection to any disk
Protector, by Computer Software Serices (CSS), for 810/1050/Indus GT, 1983
- Includes hardware and software
- Bad sector generator; also move/rearrange data, scramble directories
Silencer, by CSS, for 810/1050, 1984
- Eliminates loud drive sounds when reading bad sectors
- Write to both sides of any disk without notching disks
Over-Write [810 version], by Computer Support, 1985
- Write to side 2 of any disk without notching out a hole in the disk
Bad Sector, by Computer Support, 1985
- Write bad sectors to any diskette; can backup some protected disks
Electronic Phantom Sector Maker, by CSS, 1987 (Antic 9/87p28)
- Installs into any drive, no other modification needed
    - Can be combined with other upgrades including Happy and
      The Chip/Archiver
- Make fuzzy/phantom sectors or fuzz portions of sectors
- Find/Display valid data, CRC errors and phantom sectors
- Deluxe version: Allows you to switch between CRC and phantom sectors
   without having to readjust hardware module each time
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