The DECstation 3100 (aka the PMAX) was a system based on the same motherboard as the VAXstation 3100, except with a MIPS processor.   It was the first time that Digital had built a system using another company's chip architecture.

We had a choice between supporting the MIPS R2000 chip as "big endian" or "little endian".   We chose to support "little endian" to be compatible with PDP-11s, VAXen and Intel chips, rather than be compatible with other manufacturers.   This, in my mind, was very important since it let us share data over NFS and give greater compatibility with programs and libraries of applications already running on other Unix-like systems such as Ultrix, BSD, etc.   Sun experienced this grief when they ported Solaris off the big endian Motorola and SPARC chips to little endian Intel.

One of the few issues of the DECstation 3100 (and 2100, known as the "PMIN" after that) was that the serial I/O port did not support hardware handshaking.   To save a couple of pennies per system the VAX hardware designers determined that having full hardware modem control (DECstandard 52) on the board was not needed, because "very few workstation users hook a modem up to their serial line".   What they meant was that "very few VMS workstation users hooked a modem up to their serial line", opting for DECnet to handle their networking.   Therefore the pins necessary to support hardware modem control were missing from the DECstation product lines.

Unix users, on the other hand, often had modems hooked up to their workstation, to handle cu(1), uucp(1) and other serial line protocols.   We eventually got around this by better refining software modem control, but it was painful.

The proposal, design and release of the DECstation 3100 was a top-secret project inside of DEC, kept secret from even many people in the Digital Unix group in Nashua, New Hampshire.   The development of the system was done in Palo Alto's WorkStation Engineering group and the software engineering was done in the Western Software Labs in Palo Alto, albeit by taking key engineers from the Nashua facility and transplanting them temporarily to Palo Alto.

The implementation was kept so secret that it caught Dave Cutler, then working on DEC's next-generation operating system and chips, by surprise when it debuted at a Board Meeting in Maynard, Massachusetts.   Shortly after that board meeting Mr. Cutler left Digital and moved (with some of his team) to Microsoft.

The DECstations only were manufactured for a couple of years, as the DEC Alpha processor replaced MIPS in Digital's lineup.   Although originally promised that OSF/1 would be ported to the DECstation line, this port was dropped due to realizing that there would never be an application base to support the customers of a DECstation OSF/1 port.   It was better for ISVs and customers to maintain the Ultrix base for the DECstations than to split the base into Ultrix and OSF/1.

md