Exatron Stringy Floppy
A continuous-loop tape drive for home computers, introduced in 1978.
The Exatron Stringy Floppy (ESF) was a continuous-loop tape drive that Exatron first presented at the 1978 West Coast Computer Faire. It was designed as a middle ground between the high cost of floppy disk drives and the slow speed of audio cassette recorders. The system used small "wafers"—continuous loops of tape about the size of an American business card—that moved in a single direction and did not require rewinding. However, because data could only be accessed sequentially, the drive had to scan the entire loop to find a file, and a complete pass through a 16 kB wafer took between 55 and 65 seconds.
Exatron sold roughly 4,000 units of its ESF-80 model for the TRS-80 by August 1981, priced at $249.50. A later version for the VIC-20 and Commodore 64 was listed at $199.50 in July 1983. The company produced two incompatible wafer formats: the Model 1000, which ran at 7200 baud, and the faster Model 2000, at 11400 baud. By 1983, Exatron had rebranded as Entrepo, and the ESF continued to be sold via mail order through A&J Microdrive until 1986.
The ESF used Manchester encoding, with code written by Li-Chen Wang. Unlike later tape systems, it did not warn users before overwriting existing data. Wafers were available in lengths from 5 to 75 feet. Texas Instruments licensed the ESF for its canceled TI 99/2 computer and a never-shipped Compact Computer 40 peripheral. Models were also produced for the Timex Sinclair 2068, ZX80, and ZX81. The drive was initially used in the Prophet-10 music synthesizer but was later replaced by a Braemar micro-cassette drive due to reported reliability issues.
A 1981 Naval Postgraduate School study found the ESF-80 faster than a standard cassette drive but significantly slower than an 8-inch or 5.25-inch floppy disk. A July 1983 review in *Compute!'s Gazette* praised the ESF as a faster alternative to data cassettes, noting it could outperform some low-quality hard disks, but criticized the lack of commercially available software on wafers. Like other tape-based formats, the ESF eventually faded from use as floppy disk prices dropped in the 1980s.
- Introduced
- 1978
- Manufacturer
- Exatron
- Baud rates
- 7200 baud (Model 1000), 11400 baud (Model 2000)
- Msrp 1981
- $249.50 (ESF-80)
- Msrp 1983
- $199.50 (ESF-20/64 for VIC-20 and C64)
- Units sold by august 1981
- about 4,000 ESF-80 drives
- Tape lengths
- 5 to 75 ft
Lore & Background
By the late 1970s, computer hobbyists and manufacturers sought alternatives to floppy disks and data cassettes. Floppy disks offered quick read/write times and random access but had high entry costs, while data cassettes were slower and sequential but extremely cheap. Exatron developed the ESF as a compromise, introducing it at the 1978 West Coast Computer Faire. An ESF-80 version for the Radio Shack TRS-80 followed in 1979. The system used continuous-loop wafers, similar to an 8-track cartridge, moving in a single direction. A photocell and indicator marked the start of the tape loop. Wafers were nearly the size of an American business card, about 3/16 in thick and 1/16 in wide. Loop systems did not need rewinding but required advancing through the remainder of the tape to access earlier files. The drive scanned the tape loop, stopping to read each file header; a complete cycle through a 16 kB wafer took 55 to 65 seconds. The ESF did not automatically prevent overwriting existing data; users had to verify the tape section before writing.
Reader's Guide
The Exatron Stringy Floppy represented a transitional storage technology that attempted to bridge the gap between cheap but slow data cassettes and fast but expensive floppy disks. Its higher baud rates—7200 for Model 1000 wafers and 11400 for Model 2000—offered a speed advantage over traditional audio cassette recorders, which operated at 250–500 baud. However, the format lacked random access and faced competition from other proprietary tape systems. Exatron sold about 4,000 ESF-80 drives by August 1981, and later models for the VIC-20 and Commodore 64 were priced at $199.50 in 1983. The system was used in the Prophet-10 music synthesizer but was replaced due to reported unreliability and poor mutual compatibility. Texas Instruments licensed the ESF for its cancelled TI 99/2 computer and a Compact Computer 40 peripheral that never shipped. Models were available for the Timex Sinclair 2068, ZX80, and ZX81. The format ultimately failed to gain widespread adoption as floppy disk costs dropped, and Exatron rebranded as Entrepo in 1983. The ESF was sold via mail order into 1986 by A&J Microdrive.
Did You Know?
- The Exatron Stringy Floppy used Manchester encoding, achieving 14K read-write speeds.
- The code controlling the device was developed by Li-Chen Wang.
- Wafers were available in tape lengths ranging from 5 to 75 ft.
More in Computer Storage 1-24
Spotted an error? Know more?
Reader corrections go straight into our review queue. Suggest an edit · How this site is sourced