TOPS (file server)
| Company type | Private |
|---|---|
| Industry | Software, Networking |
| Founded | July 1985 |
| Fate | Acquired by Sun Microsystems; rebranded as TOPS; division later renamed Sitka and closed in 1993 |
| Successor | Sitka (division) |
| Products | TOPS (Transcendental OPerating System), FlashTalk, TCP/IP stacks for Mac and Windows |
| Owner | Sun Microsystems (after acquisition) |
TOPS (Transcendental OPerating System) is a peer-to-peer LAN-based file sharing platform best recognized for its implementation on the Macintosh, with versions also available for DOS and compatibility with Unix's NFS. Initially created by Centram Systems West, the company was later purchased by Sun Microsystems to bolster Sun's NFS environment. Following the acquisition, Centram was rebranded as TOPS. The product's popularity waned after the release of System 7, which incorporated a comparable native file sharing feature, prompting Sun to transfer their NFS-related projects to Sitka.
Early versions
During the 1980s, when networking protocols were largely incompatible across different systems, TOPS was developed amid Apple's unsuccessful Macintosh Office project and its efforts on the Apple Filing Protocol (AFP) over AppleTalk. Centram designed TOPS as an autonomous alternative after the discontinuation of Macintosh Office.
Launched in July 1985, TOPS addressed a market void as the pioneering peer-to-peer file sharing solution tailored for Macs. While AppleTalk was initially aimed at printer connectivity, Apple's own file sharing product, AppleShare, appeared later and necessitated a dedicated server machine such as a Mac Plus. TOPS provided an affordable option for smaller workgroups and achieved widespread use, sustaining approximately 600,000 client installations even after AppleShare became available.
The system employed a proprietary protocol grounded in remote procedure calls restricted to TOPS clients. To overcome PCs’ lack of networking capabilities, Centram introduced LocalTalk adapter cards and a PC-compatible TOPS client, facilitating seamless file transfers between Macs and PCs with automatic filename translation.
FlashTalk
In June 2013, Centram unveiled FlashTalk, a networking technology that enhanced LocalTalk speeds via external clocking. The Mac’s Zilog SCC serial ports operated internally at 3.6864 MHz, capping LocalTalk performance at 230.4 kbit/s. FlashTalk utilized an external clock source connected through the serial port to achieve higher data rates when paired with suitable hardware.
This solution combined a LocalTalk-style interface dongle with an external clock and dedicated power supply, enabling TOPS to operate at speeds up to 770 kbit/s—far surpassing standard LocalTalk and competitive during an era when 1 Mbit/s networks were becoming standard.
TCP/IP Support
Following Sun’s acquisition of Centram in April 1987, TOPS was assigned the task of facilitating access to Sun file servers via NFS. To accomplish this, Centram adapted their file-sharing protocol for use over TCP/IP. Since neither Mac OS nor Windows had built-in TCP/IP support at that time, the TOPS Division developed full IP stacks for both platforms. Their prior experience included creating a TCP/IP stack for their "TOPS Terminal," a freeware Telnet client designed for Mac.
Most Macintosh machines relied on LocalTalk or PhoneNet connections and lacked direct Ethernet access to Unix LANs. To bridge this divide, TOPS implemented support for the emerging "KIP" (Kinetics Internet Protocol) standard, which encapsulated TCP/IP packets within AppleTalk frames for transmission over LocalTalk networks. Specialized KIP bridges then converted these packets back into Ethernet format.
One drawback of this TCP/IP implementation was its lack of DNS functionality, requiring users to input IP addresses manually. However, since DNS usage was uncommon in predominantly Mac or Windows environments at the time, this limitation had minimal impact. KIP alleviated addressing challenges by utilizing AppleTalk's Address Resolution Protocol (AARP) to identify remote hosts and associate them with their IP addresses.
Additionally, TOPS incorporated the "InBox Personal Connection" email system—originally created by Symantec—thereby expanding its communication capabilities.
Decline
Following the introduction of System 7 in 1991, which featured an integrated file sharing server surpassing TOPS in performance, TOPS experienced a notable downturn in its market standing. Initially contending with AppleShare, TOPS saw a steep reduction in sales. Subsequently, Sun Microsystems separated the division into Sitka before ultimately ceasing its operations in 1993.