World Library  
Flag as Inappropriate
Email this Article


Article Id: WHEBN0000988418
Reproduction Date:

Title: Uniservo  
Author: World Heritage Encyclopedia
Language: English
Subject: 9 track tape, Tape drive, UNIVAC Tape to Card converter, UNIVAC Card to Tape converter, TX-2 Tape System
Collection: Univac Hardware, Univac Storage Devices
Publisher: World Heritage Encyclopedia


The UNISERVO tape drive was the primary I/O device on the UNIVAC I computer. Its place in history is assured as it was the first tape drive for a commercially sold computer.

The UNISERVO used metal tape: a 12-inch-wide (13 mm) thin strip of nickel-plated phosphor bronze (called Vicalloy) 1200 feet long. These metal tape reels were very heavy. Data was recorded in eight channels on the tape (six for the data value, one parity channel for error checking, and one timing channel) at a density of 128 bits per inch. The tape could be moved at 100 inches per second, giving a nominal transfer rate of 12,800 characters per second. Data were recorded in fixed size blocks of 60 words of 12 characters each. Making allowance for the empty space between tape blocks, the actual transfer rate was around 7,200 characters per second.

The UNISERVO supported both forward and backward modes on read or write operation. This offered significant advantages in data sorting and merging applications. The data transfers to/from the UNIVAC I processor were fully buffered in a one block dedicated memory, permitting instruction execution in parallel with tape movement and data transfer. The internal serial data path permitted inserting a tape data block into main memory in one instruction.

UNIVAC continued to use the name UNISERVO for later models of tape drive (e.g., UNISERVO II, UNISERVO IIIC, UNISERVO VIII-C) for later computers in their product line. The UNISERVO II could read metal tapes from the UNIVAC I as well as use higher density PET film base/ferric oxide media tapes that became the industry standard. While UNIVAC was first with computer tape, and had higher performance than contemporary IBM tape drives, IBM was able to set the data interchange standard. UNIVAC was later forced to be compatible with the IBM technology.

Technical details

The tape motion in the UNISERVO I was controlled by a single capstan connected to a synchronous motor. Supply and take-up reel motion was buffered via a complex pulley-string-spring arrangement, as the design was prior to the invention of the vacuum column buffer. The tape drive contained a permanent leader and each tape reel had a connector link to the leader. The nickel plated phosphor bronze tapes were very abrasive and to counter this problem, a thin plastic wear tape was slowly moved over the recording head, between the head and the tape, preventing the recording head from quickly wearing out. The metal tapes also were dirty and a slowly renewed felt wiper collected tape debris. The UNISERVO I had a high speed rewind capability and multiple drives on the UNIVAC I could rewind while others continued with data processing reads or writes. Phase encoding (Manchester) was used to record the information.

The later UNISERVO IIA and IIIA omitted the plastic wear tape and felt wipers, since they were primarily used with PET film base magnetic tape. Both continued the use of phase encoded recording and single capstan drives and were vacuum column designs. The IIIC and later tapes used NRZI encoding to be compatible with the IBM 729 series tape drives which set the industry standard for data interchange. Ironically, IBM then later switched to phase encoding in its 1600 bit per inch tape generation because of its superior data reliability.

See also

This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.