It comes with 1 or 2 drives an is menu driven with easy keyboard commands. You can SAVE and LOAD programs at 1100 BAUD on microcassettes. The CAI/ESF is used with the CAI/O board.
The predecessor to MDV.
From “The Timex/Sinclair Directory” by E. Arthur Brown Company, 1983.
The “Stringy-Floppy” mass storage device is probably the only system available in the US that allows true disk-like capabilities. The CAI/ESF allows you to access specific data without LOADing everything into RAM. It operates on a continuous loop of magnetic tape at very high speed so that information retrieval is not only possible, but fast.
In order to access specific data files without LOADing everything into RAM. a computer must have the capability to selectively read outside data. The TIMEX-Sinclair doesn’t come equipped to do this. However, it can do it through the proper interfaces. And that is what CAI has done with their ‘Stringy-Floppy’ system. The interface is called the CAI/O board. Since you’d have to have some sort of disk interface to connect up to a disk drive anyway, the CAI/O board in no way diminishes the value of the stringy floppy. At this writing, there are no disk drives that I know of that come near its price of only $119.95. The CAI/O board sells for $79.95. (Incidentally, the CAI/O board connects up to a lot of other things as well, like printers and modems.)
The Stringy Floppy is part of a new generation of mass storage devices manufactured specifically for the T/S computer. It lets you access your programs and data at near the speed of a floppy disk. For example, a 10ft. tape cartridge holds 15K of data and can be LOADed in 10-15 seconds. For comparison, a standard cassette player operates at about 250 baud (bits/second) while the Stringy Floppy operates at 11,000 baud. Unlike the sensitive volume and tone controls of a cassette, the CAI/ESF is preset to communicate only with the T/S computer… it LOADs perfectly every time.
Since the Stringy Floppy connects to the CAI/O board on the back of the computer, it leaves the cassette player parts available for ease of program transferring from cassette to Stringy Floppy. You won’t have to worry about incompatibility with all of the software currently available on cassette tapes.
I mentioned before that it has the ability to selectively search and retrieve data, It can do this while a program is running as well. This gives the T/S the capability of computerized letter generation. More specifically it can run a word processing program for a form letter, access names, addresses and other information from a mailing list, and fill in the blank, to produce a personalized looking letter. Of course all of this depends on the availability of compatible software.
The Stringy Floppy is menu driven. A menu is displayed on the TV screen giving you LOAD, SAVE and FORMAT options. It’s all operated directly through the computer keyboard. You can set up the CAI/ESF to bring programs into the computer while RUNning – no need to enter ‘RUN’. Tape loop cassettes are available in 5. 10, 20, 25, 35 and 50 foot length taking approximately 1 minute to cycle completely. The system is also capable of handling two drives increasing memory and speed of data access. The CAI/ESF comes with 2 tutorial programs and a manual.
That was in 1983 when disk drive prices were very high. Even the disks themselves were on the order of up to $2.00 each for 5.25″ disks while the drives were close to $200 each plus the disk interface. That was one reason that the T/S computers were so slow to have disk drive interfaces available, those that went to disk drives had money to spend.
The CAI/ESF uses a special tape cartridge called a wafer. The wafer is 2 21/32″ long by 1 9/16″ by 7/32″ thick. The tape itself is 1/16″ wide and like the tape in an 8-track audio cassette is endless.
To call the CAI/ESF into use you key in the following:
PRINT USR 10246 (ENTER)And you get the menu:
ZX-81 ESF MENU 1. LOAD 2. SAVE 3. CERTIFY 4. BASIC 5. SELECT DRIVE
The ESF SAVEs to a file number. It does not use file names so you have to keep a list to be able to know what is on a wafer. It does not assign file numbers as you SAVE but you supply the number and if you reuse a number it will overwrite the previous data under that file number. If you had five files on a wafer and reSAVEd the 2nd file (#2), I don’t know exactly what would happen if the reSAVEd file was longer than the first but I suspect that part or all of the third file would be overwritten. There is no wafer directory nor minimum file size on the wafer,
The operation is rather simple and surprisingly reliable. I will take you through the steps to start out with a brand new wafer. Like a disk for a floppy drive the wafer has to be certified (FORMATted). From the CAI/ESF menu you select 3, the computer will ask for a file number, just press ENTER. The screen will go blank and the motor light will come on. Then when the tape reaches the foil joint the other light will come on. The FORMATting is verified and the total byte count is displayed on the screen above the menu. If a specific file number is given, the FORMAT (certify) will start at that file number and certify to the end of the tape.
The only problem was that I found two wafers that self destructed, that is the tape parted at the splice/foil and tangled up inside the CAI/ESF mechanism. I had to disassemble the unit on one tape to get the tape out. In the other the tape did not get tangled-up inside the mechanism. In both cases the wafers were no longer usable. The wafers that self destructed were solid black and had labels from A & J. Since I have tested all the wafers (except for some new ones still sealed in plastic bags) there should be no more problems. It was amazing how few moving parts were inside the CAI/ESF.
When any other wafer option is selected the computer will ask for file number. And when ENTER is pressed the CAI/ESF goes into action. While I did not test it, I believe that the CAI/ESF does not really know what order the files are in. I think that at the end-of-file (EOF) marker there is a way for the CAI/ESF to determine that here is a certified space to put a file. If the SAVE is too long, it tries to SAVE on the foil splice, there will be an error message to that effect. In the SAVEing process, it seems to go through the tape to get the foil marker.
When you LOAD a file number and that number does not exist on the wafer; the CAI/ESF goes through the tape from foil to foil before reporting that the file can’t be found. However if you have LOADed a file and then LOAD the next file there is almost no elapsed time between the pressing of ENTER and the appearance on the screen of a successful LOAD.
The wafers can be write protected by removing a white dot. Somewhat like the 3.5″ disks, to uncover an opening that write protects the recording medium. Just the reverse of the 5.25″ disks.
The CAI/O is powered from the computer but the ESF is powered by a 12 VAC .93 amp. transformer. It has the ESF plugged into the rear of it while the right side of the CAI/O has the standard Timex port connector.
There are instructions for program chaining and a chapter in the 16 page manual for machine code buffs. For instance “WEOF 280F ENTRY: A=File number. Used to write the EOF marker.”
The only real advantage over cassette is that it is so much faster. With the available LOAD AIDS the dependability of a person’s own system is great. The undependblility appears only when you try to LOAD cassettes from a different machine.
There are programs to accelerate the baud rate of the SAVEing and LOADing routines. The CAI/ESF is an interesting concept that just didn’t make it like 8-track cassette systems.