Coleco ADAM Digital Data Pack

From Just Solve the File Format Problem
Jump to: navigation, search
File Format
Name Coleco ADAM Digital Data Pack
Released 1983

The Coleco ADAM Digital Data Pack (DDP) is a variant of an Audio Cassette used for data storage on a Coleco ADAM home computer, storing data and programs (including Coleco ADAM SmartBASIC tokenized files).

While these look like normal cassettes, they are not directly interchangeable; a hole on the case is in a different position than on a standard audio cassette, which prevents audio cassettes from being inserted into Coleco ADAM tape drives or ADAM data packs being inserted in audio cassette players, though "hardware hackers" have succeeded in making such uses by drilling appropriate holes.

Common tape copiers of the 1980s, such as ghetto-blasters and boom boxes are perfect for copying ADAM cassettes. After drilling the appropriate holes (a drill press makes this easy), all it takes is pressing PLAY on one cassette and RECORD on the other. Both sides of the cassette need to be copied. An hour or so later, and you have a perfect Data Pack copy.

Contrary to popular opinion, it does not require an expensive cassette to duplicate an ADAM Data Pack. Many different types of tapes have been used in copies, and even unbranded cheap bulk audio cassettes will work as long as the tape duplicator is of adequate quality. This fact is in contrast to the commonly assumed (but incorrect) idea that it takes a very high-quality cassette to work reliably under the conditions of the Adam drive. Even though the ADAM stores data at a high density and advances and rewinds the tape at high speeds (to do random access of data blocks), even bulk-bought inexpensive cassette tapes can be modded for use.

ADAM only recognizes cassettes when they're formatted. So just drilling some holes in a blank audio tape will not make an ADAM recognize a homemade Data Pack. New, store-bought ADAM tapes come pre-formatted, but any other cassette being prepared for use on an ADAM needs to be formatted first on a special machine designed for it, since the ADAM itself isn't able to format a tape. An easy way to create formatted DDPs, without access to the proprietary formatting hardware, is to simply copy an empty store-bought Digital Data Pack onto a blank audio cassette with properly drilled holes. You can easily make your own blank formatted Digital Data Packs using just a tape copier and a drill.

Both home-made and store-bought ADAM Digital Data Packs suffer from occasional explosions due to the extreme high-speed of the drive. Sometimes the drive door for the Digital Data Pack can become ajar, and the tape will "explode" inside the DDP shell, winding tape around the cassette cogs.

The tape drive uses two tracks of the tape, and has two basic formats for storing data: GW and HE. Each of them stores a total of 256 kilobytes in 1-kilobyte blocks, using 128 blocks per track.

The GW format stores blocks 0 through 7F (hex) in order on the first track (track 0), and similarly 80 through FF on the second track (track 1).

The HE format stores 40 through 7F, then blocks 0 through 3F, on track 0, and 80 through FF in order on track 1.

GW-format tapes are used to store data sequentially without any directory structure or filesystem, and the Adam's operating system offers no ability to copy this format.

HE-format tapes can have an EOS file system (the native OS of the Adam) with a directory, and are treated similarly to disks by the Adam.


Personal tools