Tymshare

Tymshare, Inc.

Company type	Private
Industry	Time-sharing services, data networking, electronic data interchange, credit card and payment transaction processing, database management systems
Founded	1964 (1964)
Founder	Thomas O’Rourke, David Schmidt
Defunct	1984
Fate	Acquired by McDonnell Douglas
Successor	McDonnell Douglas Tymshare
Headquarters	Cupertino, California , United States
Area served	United States, Europe (Belgium, UK, Germany), worldwide via network
Key people	LaRoy Tymes, Norm Hardy, Joseph Rinde
Products	Tymnet network, TYMCOM-X operating system, Tymnet II, OnTyme eMail platform, Express database system
Number of employees	100 (by 1969) (1969)
Parent	McDonnell Douglas (from 1984)

Tymshare, Inc operated as a provider of time-sharing services and third-party hardware maintenance, competing with firms such as CompuServe, Service Bureau Corporation, and National CSS. The company both developed and acquired technologies spanning data networking, electronic data interchange (EDI), credit card and payment transaction processing, as well as database management systems. From its founding in 1964 until 1984, Tymshare was based in Cupertino, California. In 1984, McDonnell Douglas purchased the company. Following organizational restructuring and asset sales through 2004, much of Tymshare's network infrastructure was ultimately decommissioned; however, certain technologies continued to be utilized within EDI applications up to 2008.

After McDonnell Douglas merged with Boeing, ownership of Tymshare’s technological assets transferred to Boeing, British Telecom (BT), Verizon Communications, and AT&T Inc. as a result of subsequent corporate consolidations.

Founding and Early Development

Established in 1964 by Thomas O’Rourke and David Schmidt—both formerly employed at General Electric’s Computer Department—Tymshare entered the nascent time-sharing industry. Initially centered on the SDS 940 system running the Berkeley Timesharing System, the company experienced rapid growth; by 1969 it maintained three sites staffed by 100 employees operating five SDS 940 machines.

In 1968, LaRoy Tymes and Norm Hardy engineered a minicomputer network functioning as nodes interfacing with mainframe computers. Beginning with General Automation’s 12-bit systems and subsequently adopting the 16-bit Varian 620i, these nodes executed a "supervisor" program responsible for routing, diagnostics, and statistical analysis, while a local "leprechaun" program managed user authentication and security protocols. The supervisor software was crafted in assembly language by Tymes under Hardy’s system design guidance. By 1972, the Tymnet network linked 40 cities across the United States featuring centralized password management, statistical multiplexing techniques, flow control mechanisms, and robust security measures.

Tymshare expanded its footprint through acquisitions including Dial Data (1968), United Data Centers, Alan-Babcock Computing, Bancard of Rhode Island, and TeleCheck. Recognizing performance constraints with the SDS 940 platform, Joseph Rinde initiated a port of the Supervisor software to the 32-bit Interdata 7/32 and 8/32 systems in 1972. Due to inadequate performance on the Interdata 8/32, development began on a more powerful machine tailored for running Supervisor.

During the early 1970s, Tymshare extended operations into Europe via CEGOS-Tymshare in partnership with Credit Lyonnais, establishing offices in Brussels (1973), the United Kingdom (1974), and Germany through Taylorix-Tymshare GmbH (1976). Taylorix-Tymshare provided solutions such as the "OnTyme" eMail platform built on Tymnet infrastructure and the multi-dimensional database system "Express," which supported marketing analytics for major corporations like Johnson & Johnson. Taylorix-Tymshare ceased activities in 1986.

A second-generation Supervisor software iteration known as "Engine" was introduced in 1974; it operated both on Supervisor-class machines and network nodes. Development of Tymnet also progressed on the PDP-10 platform, culminating in a sale of Tymnet software to TRW Inc., which established its own private network named TRWNET.

Throughout the 1970s, Tymshare created its proprietary operating system TYMCOM-X for PDP-10 computers. This OS featured random access file systems, paging with working set management, and support for spawnable processes. Notable contributors included Bill Weiher, Vance Socci, Allen Ginzburg, Karen Kolling, Art Atkinson, Gary Morgenthaler, Todd Corenson, Murray Bowles, Randy Gobbel, Bill Soley, and Darren Price. The majority of Tymnet development activities transitioned onto TYMCOM-X.

The company also acquired the Augmentation Research Center from SRI International. Following this acquisition, Tymes and Rinde developed Tymnet II, which operated concurrently with the original network on Varian hardware before eventually replacing it. Tymnet II introduced architectural enhancements that significantly increased scalability through an alternative method for constructing virtual circuits.

Separation of Tymnet, Inc.

In 1976, Tymnet Inc. was separated from Tymshare Inc., becoming an FCC-designated "common carrier." This status allowed Tymnet to offer a wider range of communication services while subjecting its pricing to regulatory oversight. The Tymnet network facilitated remote connections between host computers and terminals, enabling users to access or resell computer time through the network, with Tymnet billing for usage accordingly.

Acquisition of Tymshare by McDonnell Douglas

McDonnell Douglas Tymshare

McDonnell Douglas Corporation purchased Tymshare, including Tymnet, in 1984 and rebranded it as McDonnell Douglas Tymshare, undertaking significant restructuring. By 1985, the company divided Tymshare into several divisions—MD Network Systems Company, MD Field Service Company, MD RCS, among others—commonly referred to as the Alphabet Soup period. Despite incorporating Microdata Corporation into its Information Systems Group alongside Tymshare’s assets, McDonnell Douglas found it challenging to fully capitalize on Tymnet’s telecommunications potential. After five years and seeking liquidity amid global disarmament trends, they sold MDNSC and MDFSC profitably.

Sale of MDC Network Systems Company to British Telecom

BT Tymnet, BT North America, BTNA

On July 30, 1989, British Telecom announced its acquisition of McDonnell Douglas Network Systems Company; simultaneously, MD Field Service Company was spun off as NovaDyne. Following Boeing’s acquisition of McDonnell Douglas, the latter exited these operations. British Telecom aimed to strengthen its international data network footprint by acquiring Tymnet. On November 17, 1989, MDNSC was renamed BT Tymnet with headquarters in San Jose, California. BT established ongoing development teams across the Americas, Europe, and Asia-Pacific regions and rebranded its offerings as Global Network Services (GNS).

BT reinvigorated Tymnet by creating new hardware and software solutions leveraging relationships with telecom vendors. It piloted "TURBO engine nodes" utilizing Motorola 68000 processors. During the late 1980s, development of node code shifted from PDP-10 mainframes to UNIX environments running on Sun Microsystems’ Sun-3 and subsequently Sun-4 workstations. The original PDP-10 systems were initially retained for legacy code maintenance and documentation but were eventually retired as all development migrated to SunOS on Sun-4 servers.

Before BT’s takeover, a migration project had begun transferring Tymnet’s codebase from PDP-10 systems to Sun platforms under the Code Generation Systems (CGS) initiative. Initially supported by six Sun-3/280 servers, this transitioned to a pair of redundant Sun-4/690 servers managing source code and binary files for over 6,600 nodes and 38,000 customer interfaces worldwide. A disaster recovery failover setup was established in Pennsylvania.

Tymnet continued expanding and occasionally experienced maximum load during high-demand events—for example, during a live online chat with Michael Jackson on AOL when call volumes surpassed the network’s capacity.

MCI, NewCo, Concert

In 1993, British Telecom and MCI Communications reached an agreement known as the "Deal of the Century," whereby MCI acquired Tymnet’s U.S.-based operations and formed a joint venture initially called "NewCo," later named "Concert." Concert complemented BT’s acquisition of Synchordia in Atlanta. Tymnet was marketed under names such as The Packet network, the BT/MCI network, and Concert Packet-switching Services (CPS). MCI planned to capitalize on Tymnet’s extensive U.S. presence with over 150 points of presence (POPs) across cities to broaden local service offerings. Although MCI anticipated a decline in Tymnet usage, it remained a profitable asset.

By May 1994, approximately 5,000 nodes operated across 30 countries within the network. Key protocols included X.25, asynchronous terminal and host interfaces (ATI/AHI), and SNA. Following the failure of the Turbo nodes initiative, BT and Concert outsourced protocol integration efforts to Telematics International. Telematics adapted Tymnet protocols for their ACP/PCP frame-relay hardware; these super-nodes created a mesh network spanning Europe, Asia, and the Americas with high-speed data connectivity.

Meanwhile, MCI pursued transitioning Tymnet protocols toward TCP/IP using SPARC technology by rewriting supervisory software in C for UNIX systems running Solaris. Despite limited investment levels, this project was regarded internally as more advanced.

With the growing dominance of the Internet and World Wide Web, upgrades were necessary for Tymnet to support TCP/IP and related Internet protocols. Both BT and MCI opted not to compete directly with Internet services but focused on migrating customers toward IP-based networks while continuing to generate revenue from existing profitable Tymnet services.

MCI, MCI WorldCom, WorldCom vs. BT, Concert

In 1997, BT sought to purchase MCI, but the transaction did not materialize. By September 1998, WorldCom completed the acquisition of MCI through a stock exchange offer that was more appealing to shareholders compared to BT’s cash proposal. WorldCom assumed control in September 1998, effectively ending the BT/MCI partnership by October 15, 1998.

Concert's headquarters in Reston, Virginia

After their partnership ended, BT and MCI WorldCom began disentangling their extensive voice and data communication infrastructures. To facilitate this separation, Concert initiated Project Leonardo to divide the networks previously shared by BT and MCI WorldCom. Over a span of five years, progress was inconsistent due to ongoing contractual negotiations that caused delays and occasional setbacks. The initiative involved transitioning customers from X.25 protocols to IP-based networks and establishing parallel services so both Concert and MCI could independently operate their respective network segments. Additionally, accounting systems were separated to guarantee precise billing for clients.

Concert and BT+AT&T's headquarters in Atlanta, Georgia

In 2000, BT created a new Concert partnership with AT&T and moved its headquarters to Atlanta, Georgia. This new alliance complicated negotiations with MCI WorldCom because AT&T and MCI were competitors in the market. The division of the Tymnet data network under Project Leonardo was never fully realized. MCI WorldCom completed migration of its services from Tymnet to IP by March 2003 and terminated its portion of the network on March 31, 2003. BT maintained operation of its segment until February 2004 when the final customer switched to alternative access solutions. The Concert alliance between BT and AT&T was dissolved on September 30, 2003, with remaining BT assets merging into BT Americas, Inc., which also included BTNA. By early March 2004, BT Americas disconnected the last Tymnet supervisors, marking the end of the network.

MCI WorldCom continued to operate a lucrative EDI business segment that depended on Tymnet for connecting Tandem computers through a proprietary X.25 interface and high-speed bi-synchronous modems for EDI clients. Prior to shutting down its Tymnet portion, MCI modified the Tymnet Engine node software to allow internal communication between X.25 and modem interfaces without needing the Tymnet Supervisor. This adaptation enabled ongoing EDI support after most of Tymnet was decommissioned. These isolated Tymnet nodes remained functional as late as 2008.

WorldCom bankruptcy

WorldCom became embroiled in a significant financial scandal that led to CEO Bernie Ebbers being removed from his position and facing federal charges. The company’s stock value collapsed to ten cents per share, forcing it into bankruptcy protection. Several months later, it reemerged under the name MCI.

AT&T sold to SBC

On January 31, 2005, SBC Communications announced its acquisition of AT&T Corp. for more than $16 billion. After completing the acquisition, SBC adopted the name AT&T Inc. to distinguish itself from the original AT&T Corp.

MCI sold to Verizon

On February 14, 2005, Verizon agreed to purchase MCI, formerly known as WorldCom, shortly following SBC’s acquisition of AT&T Corp.

Verizon was formed in 2000 through the merger of Bell Atlantic, a Regional Bell Operating Company, and GTE. Prior to becoming Verizon, Bell Atlantic had merged with another Regional Bell Operating Company, NYNEX, in 1997.

Tymshare SUPER BASIC

SUPER BASIC was a version of the BASIC programming language designed for compile-and-go use on the Scientific Data Systems SDS 940 time-sharing platform. Tymshare introduced this variant commercially around the year 1968.

Tymshare PDP-10 compatible computers

Tymshare offered a series of computers created by Foonly, branded as the Tymshare XX Series Computer Family, with particular emphasis on the Tymshare System XXVI. The Foonly F4 model was marketed under the name System 26KL, which was another designation for the Tymshare System XXVI.