World Library  
Flag as Inappropriate
Email this Article

DEC Professional (computer)

Article Id: WHEBN0001871163
Reproduction Date:

Title: DEC Professional (computer)  
Author: World Heritage Encyclopedia
Language: English
Subject: PDP-11, List of Soviet computer systems, Digital Equipment Corporation, DEC J-11, Microcomputers
Collection: Dec Hardware, Microcomputers
Publisher: World Heritage Encyclopedia

DEC Professional (computer)

The Professional 325 (PRO-325) and Professional 350 (PRO-350) were PDP-11 compatible microcomputers introduced in 1982 by Digital Equipment Corporation (DEC) as high-end competitors to the IBM PC.


  • History 1
  • Technical specifications 2
  • Clones 3
  • See also 4
  • References 5
  • External links 6


Like the cosmetically similar Rainbow-100 and DECmate-II (also introduced at that time), the PRO series used the LK201 keyboard and 400kB single-sided quad-density floppy disk drives (known as RX50[1]), and offered a choice of color or monochrome monitors.

For DEC, none of the three would be favorably received, and the industry instead standardized on Intel 8088-based IBM PC compatibles which were all binary program compatible with each other. In some ways, the PDP-11 microprocessors were technically superior to the Intel-based chips. While the 8088 was restricted to 1MB of memory because of its 20-bit address bus, DEC microprocessors were capable of accessing 4MB with their 22-bit addressing (although direct addressing of memory was limited in both approaches to 64KB segments, limiting the size of individual code and data objects). But other factors would weigh more heavily in the competition, including DEC's corporate culture and business model, which were ill-suited to the rapidly developing consumer market for computers.

Further, although the PDP-11 was a very successful minicomputer, it lacked a wide base of affordable small business software. By comparison, many existing CP/M applications (see the Rainbow 100) were easily ported to the similar 8086/8088 chips and MS-DOS operating system. Porting existing PDP-11 software to the PRO was complicated by design decisions that rendered it partially incompatible with its parent product line. Industry critics observed that this incompatibility appeared at least in part deliberate, as DEC belatedly sought to "protect" its more-profitable mainstream PDP-11s from price competition with lower-priced PCs.

The PRO was never widely accepted as an office personal computer, nor as a scientific workstation, where the market was also headed to Intel 8086, or alternately to Motorola 68000-based computers. The failure of DEC to gain a significant foothold in the high-volume PC market would be the beginning of the end of the computer hardware industry in New England, as nearly all computer companies located there were focused on minicomputers, from DEC to Data General, Wang, Prime, Computervision, and Honeywell.

Technical specifications

The PRO-325 and -350 used the F-11 chipset (as used in LSI-11/23 systems) to create a single-board PDP-11 with up to six expansion slots[2] of a proprietary CTI (Computing Terminal Interconnect) bus using 90-pin ZIF connectors. The PRO family used dual RX50 floppy drives for storage; the PRO-325 had only floppies, and the 350 and 380 also included an internal hard drive. Mainline PDP-11s generally used separate serial terminals as console and display devices; the PRO family used in-built bit-mapped graphics to drive a combined console and display.

All other I/O devices in the PRO family were also different (in most cases, radically different) from their counterparts on other PDP-11 models. For example, while the internal bus supported direct memory access (DMA), none of the available I/O devices actually used this feature. The interrupt system was implemented using Intel PC chips of the time, which again made it very different from the PDP-11 standard interrupt architecture. For all these reasons, support of the PRO family required extensive modifications to the previously-existing operating system software, and the PRO could not run standard PDP-11 software without modification.

The default PRO-3xx operating system was DEC's Professional Operating System (P/OS), a modified version of RSX-11M with a menu-driven core user interface.[2] Industry critics complained that this user interface was awkward, slow, and inflexible, offering few advantages over the command-line based MS-DOS user interface that was coming into widespread use.

Other available operating systems included DEC RT-11, VenturCom Venix, and 2.9BSD Unix.

Later, the Professional 380 (PRO-380) was introduced using the much faster J-11 chip set (as used in 11/73 systems). However, due to clocking issues on the motherboard, the J-11 chip ran at 10 MHz instead of 16-18 MHz, thus making the PRO-380 slower than a stock 11/73 system.

A PRO-380 with the Real-Time Interface option was later used as the console on high-end VAX-8800 family systems.


Like the PDP-8 and PDP-11 before it, the Professional 350 was cloned in the Soviet Union as the Elektronika-85.

See also


  1. ^ The RX50 FAQ
  2. ^ a b Melling, Wesley (June 1983). "Digital's Professional 300 Series / A Minicomputer Goes Micro". BYTE. pp. 96–106. Retrieved 5 February 2015. 

External links

  • Pro 325, 350, 380
  • The Observation Deck: UNIX, circa 1984
  • The Xhomer, DEC Pro emulator based on the SIMH/PDP-11
  • DEC's PC Challenge 1982, This corporate documentary produced by Digital Equipment Corporation (DEC) chronicled DEC's two year odyssey to bring three personal computers, the Professional 325 (PRO-325), the Professional 350 (PRO-350), and the Rainbow 100 to market, a year after IBM launched their personal computer.
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.