IDE background from TechWeb,
http://www.techweb.com/encyclopedia/defineterm.jhtml?term=ide

IDE - Integrated Drive Electronics

IDE is a type of hardware interface widely used to connect hard disks, CD-ROMs
and tape drives to a PC.  IDE was always the more economical interface,
compared to SCSI.

With IDE, the controller electronics are built into the drive itself,
requiring a simple circuit in the PC for connection.  IDE drives were attached
to earlier PCs using an IDE host adapter card.  Today, two Enhanced IDE (EIDE)
sockets are built onto the motherboard, and each socket connects up to two
drives via a 40-pin ribbon cable for CD-ROMs and similar devices and an 80-
wire cable for fast hard disks.

IDE drives are configured as master and slave.  Jumper pins on the drive
itself are used to set up the first drive on the cable as master and the
second one, if present, as a slave.

The IDE interface is officially known as the ATA (AT Attachment)
specification.  ATAPI (ATA Packet Interface) defines the IDE standard for CD-
ROMs and tape drives.  ATA-2 (Fast ATA) defined the faster transfer rates used
in Enhanced IDE (EIDE).

The following hardware interface devices allow IDE devices (such as hard disk
drives) to be connected to the Atari:

==> SmartIDE project by Bob Woolley
Uses 256 of the normal 512 byte sectors.  Point-to-point wiring project.
Articles and software at http://www.wolfpup.net/atarimods/
(Atari page by Clarence Dyson)

==> KMK/JZ IDE Hard Drive Interface
by Jacek Zuk and Konrad Kokoszkiewicz (Draco)
KMK writes (March 2005):
  This is sort of cartridge fitting in ECI+CARTRIDGE slot in XE computers.
  The box is about 1,5 cm high, 15 cm long, and its width is less or more
  equal to the XE ECI+CARTRIDGE slot. You have an ECI+CARTRIDGE connector
  at one end, and an IDE cable at the other end. The whole is cased with
  black plastic case.
  What advantage does it have over similar products?
  1) it is available and still being made;
  2) the software is maintained, you can download an upgrade for the
     internal handler, for example;
  3) it uses a well defined Atari parallel bus interface, thus no OS
     modifications or other hacks are necessary to get the machine booting
     from this device;
  4) it works fine with unmodified SpartaDOS X, SpartaDOS 3.x, MyDOS (and
     other DOS-es, but using it with DOS 2.x lacks sense);
  5) it allows you to make true partitions (up to 16);
  6) it can currently address up to 8 GB (and this is not a hardware
     limit, so an upgraded internal ROM can do more);
  7) it works with all devices which are ATA-compliant;
  8) you can use two drives (master/slave);
The Interface's internal software provides two modes: native and emulation.
The native mode uses a 512 byte physical block as a logical data sector, the
emulation mode uses the physical block to store two 256 byte logical data
sectors.  ALL existing DOSes require the emulation mode to work properly.
Maximum drive capacity: 8388607 physical blocks on each device.
Maximum number of partitions: 16
Maximum capacity of a partition: 8388607 logical sectors
Logical sector length:  256 or 512 bytes
Average speed: 58 kilobytes per second (native mode, R/W)
               32 kilobytes per second (emulation mode, reading)
               7 kilobytes per second (emulation mode, writing)
Booting from any partition
Write protection capability
8 jumpers to set the device number for the operating system
Note, that ALL existing DOSes limit the partition size to 16 MB.
Available: E-mail to: jurekQrembertow.net (q = @)
User's Manual and software downloads:
http://drac030.krap.pl/  or  http://drac030.atari8.info

==> Fine Tooned Engineering (FTe) Multi I/O II (MIO II) interface
An IDE interface.  Several exist, but it was never really released

==> msc-IDE Controller, by Matthias Belitz
*  real device for the parallel-port (PBI/ECI) of the Atari XL/XE
*  up to 240 partitions per hard disk supported
*  emulates D1: until D9: of disk devices (access to 9 partitions at one time)
*  full bootable from any partition (with standard XL-OS)
*  write protection capability
*  supports master/slave configuration
*  more than 30 KB/s file access with SPARTA-DOS 3.2 gx (reading)
*  more than 10 KB/s file access with SPARTA-DOS 3.2 gx (writing)
*  software partially supports CD-ROM and ZIP drives.
Sold out.  http://www.birmanns.de/atari/

==> Gary Morton's BadSector"A" Project
 Wants to connect his IDE drive to the SIO bus.
 http://www.alma.demon.co.uk/Atari/AtariProjects.html

==> MyIDE interface and software by Mr.Atari, Sijmen Schouten
Point-to-point wiring project.  Different units for 800 and XL, including a
cartridge version for the XL.
http://www.mr-atari.com/

==> Atarimax "MyIDE+Flash" Cartridge
Atarimax "MyIDE+Flash" Cartridge is a professionally produced IDE interface
cartridge for all 64k Atari 8-bit computers.

The new MyIDE+Flash interface combines Sijmen "Mr. Atari" Schouten's popular
"MyIDE" interface with an Atarimax 1Mbit reprogrammable flash cartridge.

The cartridge's built in 1Mbit flash system allows you to utilize the
interface and your hard disk setup in any 64k XL/XE computer, using the built-
in boot OS, without modifications to the existing hardware or operating
system.
http://www.atarimax.com/myide/documentation/

==> SIO2IDE, by Marek Mikolajewski (MMSoft)
     The SIO2IDE is a simple interface that allows you to attach any IDE
  Disk Drive to your 8-bit Atari computer. Latest interface version has the
  following main features:
      * ATARI side:
        - uses standard Atari SIO at a speed of 19200 baud
        - works with Atari High Speed SIO (US and Happy) at a speed of 52000
          baud
        - emulates Atari disks D1: to D8:
          disk D1: can be swapped with Common disk D1: (HD1_ZW jumper)
        - can be used with any Atari DOS and OS
        - can be used without any problems with other SIO devices (disk
          drivers, printers, modems, SIO2PC, second SIO2IDE etc)
        - can be easy installed inside your Atari with 2.5' laptop HD
        - is easy to configure via special fdisk.com utility software
          (changing disks sequence and active directory)
      * IDE device side:
        - all IDE ATA/ATAPI devices can be used: Disk Drives (2.5' and 3.5'),
          CD-ROMs, Compact Flash cards etc.
        - supports PC file systems, FAT16 and FAT32
        - supports CD file system, ISO9660
        - supports ATR disk images (SD, DD up to 16MB)
        - supports directory change (multiconfig)
        - is easy to configure, many text configuration files (sio2ide.cfg)
          can be stored in different directories
        - disk configuration can be checked by special checkfs.exe PC utility
          NOTE: checkfs.exe does NOT work with HDD connected via USB port
        - standard disk utilities can be used (defrag.exe, scandisk.exe etc)
        - Long File Name (LFN) support for HDD
        - TEST mode for checking HDD initialization
      * USB port side:
        - interface works as Mass Storage Class device (removable drive)
        - no drivers are needed for Windows 2K, ME, XP
        - driver for Win98 is included in this SIO2IDE package
http://www.atariarea.krap.pl/sio2ide/
http://mega-hz.no-ip.com/Angebote/SIO2IDE33/SIO2IDE33.html

==> Nathan Hartwell's IDE projects
http://www.magelair.com/