Exatron Stringy Floppy

{{short description|Magnetic tape storage format}} thumb|String floppy cassette from the mid 1980s made by California Technology International thumb|An Exatron Stringy Floppy (cover removed) designed for use with the TRS-80 Model 1

The '''Exatron Stringy Floppy''' (or '''ESF''') was a continuous-loop tape drive developed by Exatron in 1978 for home computer users. The format was one of many attempts made by manufacturers to develop a new data cassette format that was smaller and more data dense than traditional data cassettes. The like other data tape formats, the ESF wafer system failed to catch on as a removable media due to a number of competing formats and inherent speed issue with tape storage,<ref name=":2">{{Cite web |date=August 1, 1995 |title=Guide to Multimedia Storage (Le Guide des Memoires Multimedia) |url=https://apps.dtic.mil/sti/citations/tr/ADA299906 |website=Defense Technical Information Center |publisher=ADVISORY GROUP FOR AEROSPACE RESEARCH AND DEVELOPMENT}}</ref> and was eventually abandoned as the cost of floppy disk storage dropped in the 1980s.<ref>{{Cite journal |date=November 1, 1980 |title=CIRCLE COMPUTER SALES |url=https://archive.org/details/byte-magazine-1980-11-rescan/page/184/mode/2up?q=floppy |journal=Byte Magazine |volume=5 |issue=11 |pages=184}}</ref>{{Efn|An add-on 8" disk drive cost $669 in November 1980}}<ref>{{Cite journal |date=February 1, 1990 |title=COMPUTER DISCOUNT WAREHOUSE |url=https://archive.org/details/eu_BYTE-1990-02_OCR/page/n173/mode/2up?q=floppy |journal=BYTE Magazine |volume=15 |issue=2 |pages=102}}</ref>{{Efn|An add-on external 5.25 inch floppy drive cost $207 in February of 1990}}

== History ==

By the late 1970s computer hobbyists and manufacturers had begun to look for alternatives methods of data storage for home computers. The two main data storage formats for home use in 1978 were floppy disk or data cassette (repurposed audio cassette tapes and recorders).<ref name="halfhill198307" /> The 5 1⁄4-inch floppy was not introduced until 1976<ref>Watson (24 May 2010). "The Floppy Disk". Canadian Business. Vol. 83, no. 8. p. 17.</ref> and the more rigid 3 1⁄2-inch version did not appear until 1983.<ref>{{Cite book |last=Shea |first=Tom |url=https://books.google.com/books?id=zS8EAAAAMBAJ&pg=PA8#v=onepage&q&f=false |title=InfoWorld |date=1983-06-13 |publisher=InfoWorld Media Group, Inc. |pages=1,7-8 |language=en}}</ref> Floppy disks offered quick read and write times, random-access , but there was a high cost of entry for drives.<ref name=":2" /> Data cassettes were significantly slower and only offered sequential access to data, but the entry cost was extremely low.

Like other companies other companies, Exatron developed a proprietary digital cassette to offer a compromise between the two formats. The company introduced the Exatron stringy floppy drive (ESF) and accompanying "wafers"<ref name=":0">{{Cite book |title=Radio Shack Hardware Manual: Exatron Stringy Floppy Users Manual |publisher=Exatron Corporation |year=1980 |pages=1-1}}</ref> at the 1978 West Coast Computer Faire, and a "ESF-80" version for the Radio Shack TRS-80 in 1979.<ref name="halfhill198307" /> ESF wafers allowed for higher write speeds (7200 baud<ref name=":3">{{Cite web |last=Reed |first=Matthew |title=The Exatron Stringy Floppy |url=https://www.trs-80.org/exatron-stringy-floppy.html |access-date=2026-03-24 |website=trs-80.org}}</ref> for Model 1000 wafers, and 11400 baud for Model 2000) than a traditional audio cassette recorder (250 - 500 baud), but did not provide random access. Data on tape needs to be accessed sequentially, that is, the tape must be wound to the appropriate position before data can be read or written.

Exatron sold about 4,000 ESF-80 drives by August 1981<ref name="barry19810831">{{cite news | url=https://books.google.com/books?id=rD0EAAAAMBAJ&pg=PA47 | title=Stringy Floppy from Exatron | work=InfoWorld | date=1981-08-31 | accessdate=15 February 2015 | author=Barry, John | pages=47–48}}</ref>, at an MSRP of $249.50.<ref>{{Cite book |last= |first= |url=https://books.google.com/books?id=FzAEAAAAMBAJ&pg=PA47 |title=InfoWorld |date=December 27, 1982 |publisher=InfoWorld Media Group, Inc. |pages=47 |language=en}}</ref> Exatron eventually began to produce only their "Model 2000" tape, which moved at twice the speed of a Model 1000 mode. These formats were not compatible.<ref name=":4">{{Cite web |date=December 1, 1984 |title=A&J Microdrive Dealer Insert Packet |url=https://archive.org/details/a-j-microdrive/A%26J%20Stringy%20Floppy%20dealer%20packet/page/46/mode/2up |website=Internet Archive |page=47}}</ref> In July 1983, the VIC-20 and C64 model (ESF-20/64) MSRP was $199.50.<ref name="halfhill198307" /> Exatron rebranded as "Entrepo" in 1983. The ESF was sold via mail order into 1986<ref name=":3" /> by A&J Microdrive.<ref name=":4" />

== Technical information and limitations ==

The Exatron system used a continuous-loop (similar to an 8-track cartridge) which moved in a single direction<ref name=":1">{{Cite journal |last=Carlson |first=Keith |title=The Exatron Stringy Floppy Data-Storage System |url=https://archive.org/details/byte-magazine-1981-11/page/n127/mode/2up |journal=Byte Magazine |volume=6 |issue=11 |pages=128-130}}</ref>. The wafers used a photocell and indicator to designate the start of the tape loop. The wafers were almost the size of an American business card (about {{convert|3/16|in|mm|1}} thick and {{convert|1/16|in|mm|1}} wide).<ref name="barry19810831" /> Loop systems were considered advantageous since they did not need to be rewound like a traditional magnetic audio or video tape (although they did need to advance through the remainder of the tape length to access files located at earlier memory addresses). On a traditional data cassette of the era, the user would need to manually rewind the tape into the correct position.

Like all data cassette formats of the era, there is no digital single catalog of files. To load a specific file, the drive must scan the tape loop, briefly stopping to read the header of each file. Since the tape loop only moves in one direction, a file that starts behind the current location cannot be read until the read head moves over that spot on the tape{{r|halfhill198307}}. One complete cycle through a 16kB wafer takes 55 to 65 seconds, depending on the number of files it contains{{r|halfhill198307}}.

Unlike later formats, the ESF system did not automatically prevent or remind a user when they were about to write-over existing data<ref name="halfhill198307" /><ref name=":1" />. Users had to use a command to verify the section of tape they planned to write to was empty (or unwanted) before transferring data to a wafer<ref name=":0" />.

Wafers were available in tape lengths ranging from {{Convert|5 to 75|ft|m}}.{{r|barry19810831}} {| class="wikitable" |+ Model 1000 Tape Capacities <ref name=":3" /> !Kilobtyes !Length (feet) !Length (meters) |- |4 kB |5 feet |1.5 m |- |16 kB |20 feet |6.1 m |- |48 kB |50 feet |15.25 m |- |64 kB |75 feet |22.9 m |} {| class="wikitable" |+Model 2000 information<ref name=":4" /> !Length (ft) !Length (m) !Kilobtyes !Read time |- |10 feet |3 meters |14 kB |12 seconds |- |20 feet |6.1 meters |28 kB |24 seconds |- |35 feet |10.7 meters |49 kB |42 seconds |- |50 feet |15.2 meters |70 kB |60 seconds |- |62 feet |18.9 meters |85 kB |73 seconds |}

== Usage and reaction == In the July 1983 issue of ''Compute!'s Gazette'', the Exatron Stringy Floppy (ESF) for the VIC-20 and the Commodore 64 was described as a faster alternative to traditional data cassettes, and its ability to out-perform some lower quality hard disks. The main issue highlighted was the lack of software available for purchase on wafers<ref name="halfhill198307" />.

According to ''Embedded Systems'' magazine, the Exatron Stringy Floppy uses Manchester encoding, achieving 14K read-write speeds and the code controlling the device was developed by Li-Chen Wang.{{Citation needed|date=March 2026}}

Texas Instruments licensed the ESF for its cancelled TI 99/2 computer and a Compact Computer 40 peripheral which never shipped.<ref name="mace19830530saddle">{{Cite magazine |last=Mace |first=Scott |date=1983-05-30 |title=Texas Instruments in the Saddle |url=https://books.google.com/books?id=4S8EAAAAMBAJ&pg=PA26 |access-date=2024-12-29 |magazine=InfoWorld |pages=26–28}}</ref><ref name="halfhill198307">{{cite news | url=https://archive.org/stream/1983-07-computegazette/Compute_Gazette_Issue_01_1983_Jul#page/n59/mode/2up | title=Exatron Stringy Floppy for VIC-20 and 64 | work=Compute!'s Gazette | date=July 1983 | accessdate=6 February 2016 | author=Halfhill, Tom R. | pages=58–62}}</ref>. Exatron hoped to develop Apple II and Commodore PET models<ref name="barry19810831" />. Models were available for the Timex Sinclair, including the 2068, the ZX80 and the ZX81<ref name=":4" />

An investigation by the Naval Postgraduate School in 1981 described the ESF-80 version of the string floppy as a quicker alternative to a cassette drive but noted the significant delays when compared to an 8" or 5.25" floppy.<ref>{{Cite web |last=Isbell |first=Robert Paul |date=September 1, 1981 |title=Statistical Analysis Software for the TRS-80 Microcomputer |url=https://hdl.handle.net/10945/55104 |website=Defense Technical Information Center (DTIC)|archive-url=|url-status=}}</ref>

The Exatron drive was initially used in the Prophet-10 music synthesizer and was later replaced with a micro-cassette drive from Braemar, reportedly due to unreliability and poor mutual compatibility of the former.<ref name="Reid 1999">{{cite web|url=http://www.soundonsound.com/sos/mar99/articles/retroprophet.htm|title=Sequential Circuits – Prophet Synthesizers 5 & 10 (Retro)|last=Reid|first=Gordon|date=March 1999|work=Sound on Sound|archive-url=https://web.archive.org/web/20160203065241/http://www.soundonsound.com/sos/mar99/articles/retroprophet.htm|archive-date=3 February 2016|accessdate=January 23, 2015}}</ref>

== Notes == {{Notelist|liststyle=lower-alpha}}

== References ==

== External links ==

* [https://www.digibarn.com/collections/devices/stringy-floppy/ Exatron Stringy Floppy as described by Bill Fletcher] * [https://www.classic-computers.org.nz/system-80/software_esf_archive-imaging.htm Getting Files off Stringy Floppy Wafers for use in Emulators] * [http://www.trs-80.org/exatron-stringy-floppy/ Advertisements] * [https://www.exatron.com/ Exatron Official Website]

Category:Computer storage devices Category:Home computer peripherals Category:TRS-80 Category:Computer-related introductions in 1979