Mentec

Mentec International Ltd was founded in 1978^[1] and initially focused on the development of monitoring and control software and systems. It was a significant Digital Equipment Corporation (DEC) reseller and OEM in Ireland.^[1] Mentec Computer Systems Limited was a subsidiary of Mentec Limited that repackaged PDP-11 processors. Mentec Inc.^[2] was a US-based subsidiary of Mentec Limited. In the early 1980s it had a range of remote terminal units based on the SBC/11-21 (Falcon).

Once the

, the M70.

In 1994 Digital transferred the PDP-11 operating systems to Mentec Inc.^[3]

Product range

M70

The M70 was developed between 1982 and 1984. It was a quad

and 4 serial lines implemented using DEC DC319 DLART chips.

M71

The M71 was a version of the M70 intended for process control.

Remote Terminal Units

.

M80

The M80 was a further development of the M70 but using parity memory and a slightly higher clock rate. It also introduced software configuration via the bootstrap which all but eliminated wire-wrap configuration.

M90

This was effectively merely a clock tweaked version of the M80.

M100

The M100, a redesign of the 11/93, was the last of Mentec's J-11 based processor boards.[5]^[6] It ran the J-11 chipset at 19.66 MHz, and had four on-board serial ports, 1-4 MB of on-board memory, and an optional FPU. The M100 was a somewhat tidied up and faster re-design of the M90.

Some late models incorporated a daughter card with a Xilinx part which replaced the DLARTs and implemented a FIFO to prevent overruns for OEM applications. A small number of late models also incorporated an SRAM daughter card which replaced the on-board DRAM.

M11

The M11 was a microcoded implementation of the PDP-11 instruction set done from scratch, Mentec announced, describing it as a processor upgrade board replacement for the M100.^[7] It was based around two Texas Instruments TI8832 ALUs and a TI 8818 microsequencer. One of the ALUs was used as the processor ALU while the second was used to implement the memory management unit. An

. The 4 DLARTs of the earlier M100 were emulated on a single Xilinx part. All of the memory (both microcode and PDP-11 main memory) was implemented using SRAM. While not of any significant effect in the field it suffered from the fact that it used a large number of microcode controlled drivers onto tri-state buses, which made developing microcode somewhat hazardous.

The M11 design was implemented in

CPU diagnostics on the simulator before any hardware was constructed.

M1

The M1 was a processor upgrade board, done as an ASIC re-implementation of the M11's implementation of the PDP-11 instruction set. Despite being an ASIC implementation it was also fully microcoded.^[8] The M1 used an Atmel 0.85 μm ASIC for 5V operation.^[8]

PDP-11 operating systems

RSX-11

Ownership of RSX-11S, RSX-11M, RSX-11M Plus and Micro/RSX was transferred from Digital to Mentec Inc. in March 1994^[9] as part of a broader agreement.^[10] In 2006 Mentec Inc. was declared bankrupt while Mentec Ltd. was acquired by Irish firm Calyx in December 2006.^[11] The PDP-11 software, which was owned by Mentec Inc. was then bought by XX2247 LLC, which is the owner of the software today.^{[citation needed]} It is unclear if new commercial licenses are possible to buy at this time. Hobbyists can run RSX-11M (version 4.3 or earlier) and RSX-11M Plus (version 3.0 or earlier) on the SIMH emulator thanks to a free license granted in May 1998 by Mentec Inc.^[12]

Legal ownership of RSX-11A, RSX-11B, RSX-11C, RSX-11D, and IAS never changed hands; therefore it passed to Compaq when it acquired Digital in 1998^[13] and then to Hewlett-Packard in 2002.^[14] In late 2015 Hewlett-Packard split into two separate companies (HP Inc. and Hewlett Packard Enterprise),^[15] so the current owner cannot be firmly established.^{[dubious – discuss]} New commercial licenses have not been issued at least since October 1979 (RSX-11A, RSX-11B, RSX-11C)^[16] or 1990 (IAS),^[17] and no one of these operating systems was ever licensed for hobbyist use.

RSTS

In 1997 Digital and Mentec granted anyone wishing to use RSTS 9.6 or earlier for non-commercial, hobby purposes a no-cost license . The license is only valid on the SIMH PDP-11 emulator. The license also covers some other Digital operating systems. Copies of the license are included in authorized software kit available for download on the official website of the SIMH emulator.^[18]

References