9-track tape drives for the Apple. (evaluation) Stephen Arrants.
The ability to exchange data with larger computers opens up a new world of attractive applications for the Apple user. Until recently, floppy disks and Winchester drives offered the only reliable storage and retrieval media.
If a business owner wished to buy or rent mailing lists, he was faced with a dilemma. Few companies offer mailing lists or other data on Apple compatible media. The U.S. government, for example, offers a seemingly endless supply of data on nine-track tape. The FAA and FCC routinely make their files available for a small copying charge. The complete directory of the new nine-digit zip codes may be borrowed at no charge from the U.S. Postal Service.
Almost any federal data except that concerning national security, matters of personal privacy, or proprietary information is available for a reasonable fee. For an additional charge you may request a subset of the data based on income, residence, age or almost any other category. Information on government data and software is available from the National Technical Information Service, 5285 Port Royal Rd., Springfield, VA 22161.
Many private companies such as magazine publishers, polling organizations, universities, and research bureaus also offer mailing lists on magnetic tape.
An Apple with a magnetic tape drive is ideal for data collection in scientific, commercial and educational situations, or for data reduction and analysis projects in these environments.
At less than $1 per megabyte, magnetic tape is a reliable, reusable medium for archival storage, hard disk backup, and general bulk data storage. Data storage and retrieval time with a nine-track drive are speeded up to almost 20 times faster than those achieved by an Apple disk drive. For example, BLOADING the 8K hi-res buffers used in the photographs takes about nine seconds with the Apple drive. Loading from a medium speed (25 IPS) tape takes less than 0.5 seconds.
Electrovalue Industrial Inc. is a six-year-old firm specializing in the purchase of quality commercial and industrial excess inventory items for resale to computer hobbyists. We recently discovered that this company which leases space in the Creative Computing building offers a unique product designed to afford data interchangeability among the Apple, minicomputers and large mainframes.
Electrovalue's Apple 9-Track Tape Drive consists of an industry standard tape drive with Apple adapter and with cables to a small controller card. The drives are compatible wth the Apple II, Apple II+, and the Apple IIe, as well as with Apple look-alikes such as the Franklin Ace. They do not run with the Apple III.
The controller plugs into any available slot and performs all the necessary data transfer, control and formatting functions. This allows easy reading and writing of tapes via simple CALLS from Basic and/or assembly language programs. A Pascal version is under development.
Two drives currently offered by Electrovalue differ primarily in tape speed and the maximum diameter reel which may be mounted. The full size drives read and write tape at 25 IPS and handle any size reel up to the largest (10.5"). The smaller size drives run at 18.75 IPS and take up to a 7" reel.
Half-inch nine-track tape comes on standard removable reels. Tape length can vary, depending on the user's needs, from200 feet to 3600 feet. Quantity prices for ten reels range from approximately $7 to $27 dollars. An explanation of how data is formatted on tape will show how this drive provides an inexpensive method of data storage. How It Works
Two nine-track recording formats are common today: 800 BPI (bytes per inch) and 1600 BPI. The Apple drives can read and write only the 800 BPI format, which is unfortunate, since 1600 BPI format provides twice teh storage capacity and is more popular than the 800 BPI tape. This drawback is offset by several factors: 800 BPI drives are less expensive, many of the drives in commercial use are capable of dual-density 800/1600 BPI operations, service bureaus offer inexpensive 1600 to 800 BPI conversion, and popular sources of data offer both formats.
Data are written on tape in blocks of 9-bit characters (an 8-bit byte and an automatically generated parity bit), hence the term nine-track. Collections of blocks are separated into files which are delineated by special blocks called EOF (End of File) markers. Each block also contains special characters used to check the data. These are generated by the controller when writing and checked when reading.
The length of the data blocks written on tape varies, depending on the application. The ANSI standard for 800 BPI defines a maximum block size of 2K (2048 characters), but in practice this is often exceeded. The Electrovalue interface can easily handle block lengths of up to 16K. Software
The firmware I/O routines provide a versatile, application independent means of accessing the tape drive. Electrovalue provides additional programs written in Applesoft to help users get the system up and running. The Demo program transfers ASCII files from tape to screen, disk, or printer and vice versa. It handles up to 100 tape files and allows the user to specify block size when going from disk to tape.
I found this program slower than I would have expected. This was traced to the programmer's use of GET A$ and PRINT A$ for character handling. All actual I/O transfers between tape and memory ran at full speed--up to 36,000 CPS with a 25 IPS tape drive. Electrovalue is rewriting the character handling routine in assembly language and adding EBCDIC-ASCII conversion, two desirable improvements to a very versatile program.
The Diagnostic program reads and writes blocks of random data and performs other operations to check drive operation, controller, and ROM resident firmware. It runs quickly and provided excellent information when I forced an error by inserting a piece of paper between the tape and the read/write head.
Finally, a Basic Subroutine package provides a way to access quickly and easily all the tape drive functions from Basic. It contains a short application program in the form of a test which calls an integrated set of Basic subroutines. After reading the documentation, I suggest you study a listing of this program to see examples of tape drive programming. Documentation
The documentation is clearly written and extensive in scope and technical content. Don't be put off by the three-ring binder and line printing. Electrovalue prefers to maintain documentation on a word processing system in order to be able to make quick updates.
Included with the documentation are a copy of the drive manufacturer's technical manual, a review of magnetic tape format and use, a thorough description of each of the firmware I/O routines with examples, schematic diagrams of the controller and adapter boards, installation procedure, and listings of the three sample programs. After a session with the documentation, you will have enough information to get the system up and running.
A new, full size 25 IPS drive with integrated controller is $3000. A smaller and slower drive is $1800. Used, refurbished drives are available from time to time at lower prices. Drives which are compatible with Electrovalue's controller are made by Cipher, Digi-Data, Kennedy, Perkin-Elmer, Pertec, Wangco, and others.
If you have your own drive, the controller along with system cables, documentation, and software is available separately for $900. At these prices, not every Apple owner will be able to afford such a drive. However, for those users who need nine-track compatibility with other computers, who need reliable data backup, or who use Apples for large scale data collection, this is a cost-effective alternative to other storage media. Commercial minicomputer magnetic tape controllers alone sell for about $2500.
Products: Electrovalue Apple 9-Track Tape Drive (computer apparatus) - Evaluation