DEC Professional
Introduction
The Professional series was Digital's response to the emerging IBM PC desktop market. These models were geared for the business and engineering market. By contrast the DEC Rainbow computer was targeted for the business and home market. The Professional computers were superbly engineered, perhaps even over-engineered, were more expensive to manufacture and could not compete with lower cost PCs which had a wide assortment of desktop software readily available.
When these models were introduced 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. As a result, the Professional was never widely accepted as an office or personal computer, nor as a scientific workstation, where the market was headed to Intel 8086, or alternately to Motorola 68000-based computers. The Professional models were well designed products with many innovative hardware features but limited market appeal.
Digital Equipment Corporation designers decided that new machines should perform several tasks at once, apply the same user interface to each task, communicate efficiently, and, as an added bonus, use the same software as Digital's popular minicomputers. The Professional 300 Series consisted of three models that differ in storage capability, slot space and speed. The 325 has one dual floppy-disk drive and three option slots and could be upgraded to a 350 model, which had an optional Winchester hard disk and three additional slots.
The Professional 325 and 350 used the F11 chip set, the same processor as used in LSI-11/23 and PDP-11/24 systems, to create a single-board PDP-11 with up to six expansion slots of a proprietary CTI (Computing Terminal Interconnect) bus using 90-pin Zero Insertion Force (ZIF) connectors. The processing power of the Professional 325 and 350 models were aided by a floating point processor chip and memory management chip which expanded the memory to 4MBytes using 22 bit memory addressing.
The Professional family used dual RX50 floppy drives for storage; the Professional 325 had only floppies, and the 350 and 380 models included an internal hard drive. Mainline PDP-11s generally used separate serial terminals as console and display devices but the Professional family had in-built bit-mapped graphics to drive a combined console and display.
The 380 model was a faster version of the 350 utilizing the J11 PDP-11 chip which is also used on DEC's PDP-11/73. The Professional 380 (PRO-380) used the 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. The Professional Series PC-38N was a PRO-380 with a real-time interface (RTI) that was used as the console for the VAX 8500 and 8550. The RTI has two serial line units: one connects to the VAX environmental monitoring module (EMM) and the other is a spare that could be used for data transfer. The RTI also has a programmable peripheral interface (PPI) consisting of three 8-bit ports for transferring data, address, and control signals between the console and the VAX console interface.
These personal computers were desktop-sized versions of the PDP-11, one of Digital's popular minicomputers. All models shared the PDP-11 instruction set and memory management and provided the user with 90 percent of the throughput of a PDP-11/24 for the 325 and 350 models. Both had an operating system based on Digital's RSX-11M+.
Architecture
Three major components; the system
unit, the monitor, and the keyboard-
comprised the Professional
300 system series. The system
unit contains the processor, memory
options, power supply, and mass
storage in a case that measures 23.5
by 14 by 6.5 inches. The main logic
module contains the F11 central processing
unit, a chip set equivalent to a
PDP-11/23-Plus or the J11 processor equivalent to a PDP-11/73.
Its instruction set includes 87 instructions and eight addressing modes of either 16-bit words or 8-bit bytes. Although the system works with 16-bit addresses, providing for 64K bytes of logical address space, the Memory Management Unit (MMU) constructs 22-bit addresses that allowed up to 4 megabytes of random-access read/write memory (RAM).
Two on-board memory modules totaling 256K bytes of RAM connect to the main system logic module with 40-pin connectors without occupying one of the option slots. The standard configuration also included 16K bytes of read-only memory (ROM) and 32K bytes of RAM for bit-map control.
Options requiring extra memory include the necessary additional RAM on the option module. A nonvolatile clock and RAM use a rechargeable nickel cadmium battery to maintain the time and date even when the system power is turned off. Each Professional System also included a unique 47-bit identification ROM that was readable from software and could be used for either system verification or as part of a piracy protection scheme.
A 208-watt power supply with an integral fan handled a Professional 350 equipped with all available options. The disk-drive units were easily accessible from the front of the chassis. All Professional Series systems came with an RX50 dual-disk subsystem that was capable of storing up to 800K bytes of formatted data in fixed-length blocks on two 5.25-inch DIGITAL proprietary floppy disks. This subsystem included a separate single board controller module and extensive internal self-testing and diagnostic firmware.
Optional Winchester disks were available for the 350/380 models, ranging from 5 to 20 Megabytes, although higher capacity disks were used successfully. The 350/380s module cage contained six slots for the addition of peripherals. In the standard configuration, one slot was occupied by the floppy-disk controller and another was occupied by the video controller. The back panel of the system unit enclosure has connectors for a serial printer port, the video monitor port, an RS-232C/423A serial-communications port, power, an optional telephone-management interface, and a 16-pin Ethernet connector.
Communications
The Professional's designers assumed
that managers and office
workers rarely work alone. Instead,
they spend their time communicating
with others and accessing data from
larger computers, activities that require
powerful and concurrent communications
facilities. The standard
communications port on the Professional
handles asynchronous or synchronous
communications. By using
available software, the system
manages VT102, VT125, 3276 BSC,
3276 SNA, and 3780 communications.
Other communications facilities were available as options. A realtime interface module provides an IEEE-488 bus interface, two EIA RS- 232C-compatible asynchronous ports that were programmable from 50 to 9600 bps, and a 24-bit bidirectional parallel port. An Ethernet connection is also provided at the rear of the system unit, used with an optional DECNA-K Ethernet controller card.
Monitor
A 12-inch monochrome monitor
and a 13-inch color monitor are
available for the Professional Series.
The standard monochrome video
controller provides full bit-mapped
graphics with 32K bytes of memory
on the board, supporting a 960 X 240
pixel display. An
extended bit-mapped option provided
memory for two additional bit planes
as well as RGB (red-green-blue) control
for the color monitor. Both
monitors were designed to be as small
as possible to keep the computer
system's footprint-the size of the
surface it occupies-as unobtrusive as
possible.
Keyboard
The keyboard was designed to
meet three major criteria: it must conform
to international standards, accommodate
Digital's multinational
character set, and provide user-defined
function keys. Using these criteria
and basing their work on
ergonomic studies, the designers provided
105 keys and separated them
into four logical groups.
A main typing array of 57 keys conforms to the international touch-typist layout. Immediately to the right of the main keyboard are the editing pad and the cursor-control keys. The most commonly used editing keys-Find, Insert, Remove, Select, Next Screen, and Last Screen-are located just to the right of the main array. The cursor controls are arranged in an inverted T, the most efficient configuration for touch-typists. To the right of the cursor controls is an 18-key numeric pad that makes it possible to enter large amounts of numeric data quickly. The pad layout is compatible with all existing software dependent on Digital's VT100 keypad arrangement. Across the top of the keyboard is a row of 20 function keys.
Application programmers can program all but four of these keys. Digital's designers also provided a special windowed area at the top of the keyboard for key labels. Digital did extensive tests with computer novices to help ensure that the functions of the keys are obvious from their labels.
User Interface
Digital made a concerted effort on
the design of the user interface for this
family of personal computers. In all
aspects, from installation and
maintenance features to the operating
system, the designers anticipated prospective
users' habits and needs. A
novice user can install the hardware,
the operating system, and application
software and do minor maintenance
without technical help. The system
components assemble quickly. For
example, you simply connect the
keyboard to the monitor with a cable,
connect the monitor to the system
unit in the same way, plug the power
cord on the system unit, insert the
Winchester disk, plug into an AC
power outlet, and hit the switch.
Options
The
option cards were designed with zero insertion-
force (ZIF) connectors and install
on a system bus designed to eliminate
the need for switches and jumpers.
The Professional's CTI system bus
has many notable features. Like the
older LSI-11 bus, the Professional's
system bus had 22-bit addressing and
multiplexes addresses and data by
combining 16-bit data signals with
the 22-bit address signals on 22 signal
lines.
Each option module installed on the bus generated two different hardware-interrupt signals with an associated register indicating the memory location of the interrupt handling routine associated with this signal. The design of the interrupt handling hardware made the interrupt priority independent of the slot position. When the user installed a module, an option-present signal alerts the main system logic module. Because each option contains identification information in ROM, the system easily locates and identifies all installed options.
Each bus slot has a fixed address, and an option card assumes the address of the slot it occupies. And except for the hard disk and the floppy-disk controllers, any option card works in any slot.
Diagnostics
The installation of the operating
system is equally simple. A series of
copies from floppy disk to hard disk
with software prompts guide the
way. Application programs use a
similarly simple procedure under control
of an automatic installation utility.
The Professional 350 also offers
diagnostics both in ROM and on disk
that run every time the system boots.
The diagnostics for the main system
logic run first and are followed by a
segment that detects which options
are installed. Then diagnostics on
each module transfer to RAM to be
run by the central processing unit.
Error messages take advantage of the
machine's bit-mapped graphics by
drawing a picture of the system and
highlighting the failing component in
reverse video.
All the system's modules could be replaced and could be removed either with fingers or a ballpoint pen. These features reflect Digital's belief that a user who has to call a technician soon becomes convinced that the computer is complex and difficult to use.
Software Availability
Digital's design goals are further
evident in the company's three pronged
software effort: the Professional
Operating System (P/OS), the
Professional Developer's Toolkit, and
third-party application programs.
The operating system was derived
from Digital's RSX-11M+, an event driven
multitasking operating system.
The design team regarded multitasking
capabilities as mandatory. As the
personal computer becomes an integral
part of the professional's working
patterns, the designers reasoned,
the machine must function in the
same manner as its user, which means
working at multiple tasks.
Throughout the design process, the goal of a consistent user interface was cardinal. Today, some operating systems force users to have as many different interfaces as they have application packages. Digital believed that a continual proliferation of interfaces would impose a major constraint on the perceived usefulness of personal computers. P/OS removes that constraint by making it simple for programmers to work with a consistent user interface that controls every application on the system. The combination of multitasking, the user interface, and published standards, tools, and guides for application is a design that responds to the needs of the Professional's market. In the initial release of the operating system, a single menu-tree structure, help-message handler, error message handler, and a common file structure characterize the user interface.
While the hardware architecture makes it possible to take advantage of windowing and various cursor-positioning schemes such as mice or bit pads, the software design team felt that the first priority should be establishing a consistent interface. The other options will evolve as users demand them. For an example of how the user interface works, consider what happens when you want to use a new application package on the Professional system. First you insert the disk and call the automatic application installation utility, which copies the program into the program library. At the same time, the utility copies the error messages into the appropriate library, puts text in the help library, integrates the application 's menu into the menu tree, and places the name of the application package in the main menu. During this process you can also rename that application program or position it at a particular place in the menu tree.
All of the application programs Digital developed use this same installation approach. One advantage of a consistent user interface is that you can get on-line help at any time simply by pressing the Help key. Other P/OS features include a file structure protocol identical to that on PDP-11 and VAX systems, which makes file transfers between the Professional and those systems much easier. A set of file services, print services, disk utilities, and a memo editor called PROSE are included with the operating system. The designers also furnish an interactive BASIC interpreter, PRO/BASIC, to meet the user's everyday programming requirements . PRO/BASIC is a compatible subset of Digital's BASICPlus- 2 and VAX-11 BASIC, the only exception being that the PRO/BASIC has additional graphics commands. Features of the language include 31 character variable names , extended IF...THEN ... ELSE statements, single and double precision, program chaining, and online help.
Development Tools
For special applications that require
the user to design custom software,
Digital has provided the Professional
Developer's Toolkit. This
package of tools lets a programmer
use the power and resources of a VAX
or PDP-11 minicomputer to write
programs for the Professional Series
microcomputers. The Toolkit supports
seven languages
and contains programming utilities
RMS (Record Management System),
FMS (Forms Management System),
and CGL (Core Graphics Library).
In a typical development scenario on the Professional, a programmer enters and edits source code using PROSE. Then the programmer uses the communications utilities provided with the Toolkit and takes advantage of the identical file structure protocols to pass the source code to a larger PDP-11 or VAX system. The' minicomputer compiles the code and transmits the result back to the Professional system, where the programmer uses an interactive debugger to refine the program. Later, the programmer uses the frame-development tools to create menus and error messages for the program.
Additionally, an application-builder program creates floppy-disk copies for distribution. Finally, the programmer may develop algorithms that use the identification number located in ROM to combat software piracy. A Toolkit style guide helps programmers maintain the consistency of the user interface. For example, execution of a command should be initiated by pressing the DO key rather than Enter or Return.
Digital's design goal is that end users will get some applications programs from Digital, some from their own programming staff, and some from third-party vendors, but all the programs will look and act as if they came from the same programmer. Already, Professional Series users have access to software that has been developed with the consistent user interface. Much of this application software is also available for both the Professional and Digital's larger systems, and the common file structure provides an easy migration path to established minicomputer software.
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.
Telephone Management
In another example of designing a
personal computer around the work
habits of the user, Digital introduced
a Telephone Management System
(TMS) option. A potential
user of the Professional system
probably spends at least 20 percent of
the day on the telephone. That time
can be made more productive by
using TMS, which lets the computer
maintain a personal directory of
numbers, dial calls, log and file
messages, and answer the phone
when necessary. Additionally, TMS
can provide facilities for dictation
and transcription.
Perhaps most impressive
is that the TMS hardware
will support composite documents,
which combine text, graphics, and
voice-which are necessary components
of the automated office.
The TMS has three components: a
controller board that fits into the
option-card cage of the system unit,
an attachment plate that goes on the
rear of the system unit, and an accessory
box designed to resemble the
keyboard. The controller board contains
most of the TMS logic, including
the modems, DTMF transceiver,
tone-detection circuitry, Codec,
a voice encoding and decoding chip.
Bell Laboratories 103J/212A
equivalent modems provide the user
with 300- or 1200-bps (bit-per-second)
data communication over standard
telephone lines, and Touch-
Tone signals can be transmitted with
the DTMF transceiver. The tone detection
circuitry detects dial, busy,
and ring-back tones. Analog voice
signals from the telephone line or
voice unit are converted into digital
signals by the CODEC circuitry. These
signals can then be stored on the Professional's
Winchester disk, on a file
server, or on a larger system. The
process also reverses to reconstruct
analog signals from transmission on
the phone line or voice unit. A CVSD
(continuously variable slope delta
modulation) 32K-bps encoding
scheme maintains high-quality voice
playback.
A plug-in attachment on the back of the system provides modular-jack connections for two telephone lines, allowing the user simultaneous voice and data connections. Additionally, this attachment provides the necessary connections for the user 's telephone and the optional voice unit, which contains a full telephone dial pad, conference phone buttons, and dictating-machine control keys. The unit also has a speaker and a microphone.
The TMS hardware operates through a standard handset or an external speaker. In combination with an optional communication-services software package, the user can maintain a personal calling directory and automatically invoke dialing of either voice or data calls.
- Dictation: A dictation wand can be obtained as an accessory for the voice unit. Using the wand, a manager will be able to dictate text, which can be converted to digital signals and transmitted across Ethernet to a secretary's Professional Series system.
- Transcription: Using the earphone and foot pedal, which are available as accessories for the voice unit, a secretary can transcribe the dictated text.
- Voice annotation on text: Text being read from the video screen will be annotated simply by positioning the cursor where the comment is to occur. When the Comment key on the voice unit is depressed and the comment has been dictated, it will be converted from analog to digital signals and embedded in the text. The technique can, of course, be used to edit text prepared by a typist.
- Voice Messaging: The Telephone Management System, with proper application programming, wad able to accept and digitize voice messages. This ability permits the caller to dictate a message that can be appended to a text header prepared by the secretary.
Under proper program control, the TMS system can alternatively provide a complete telephone answering service.
The communications software also provides for VT102 and VT125 terminal emulation using the TMS modems and permits file transfer between other Professionals as well as to RSX and VMS systems. The hardware's potential, however, still remains to be reached, and the Professional's design ensures additional future uses. The following applications can be expected in the near future.
The CP/M Option Module consists of a Zilog Z80 microprocessor with 64K bytes of memory on-board. Included with the unit is a floppy disk containing the CP/M operating system. This option is available only for the DECmate II and the Professional Series, which do not come with a built-in Z80 processor. With the CP/M Option Module installed, the Z80 can run any of the popular CP/M software while the microcomputer's main processor is busy working on something else.
Programming Languages
- BASIC-Plus-2 is an extended BASIC compiler that offers structured programming constructs; access to global variables, functions, and constants; and support for implicit and explicit data types.
- FORTRAN 77 is an extended implementation of the ANSI (American National Standards Institute) subset Fortran-77 standard (X3.9-1978). Professional Tool Kit FORTRAN- 77 contains many of the full set language features and extensions not included in the standard. Full language features include double precision and complex data types, intrinsic functions, exponentiation forms, format editor descriptors, and generalized DO loop parameters.
- COBOL 81 is based on the 1974 ANSI COBOL Standard (X3.23-1974) and includes some of the features planned for the next standard.
- DIBOL allows for the use of P/OS system services while maintaining many of the standard DIBOL features found on VAX/VMS, RSTS/E, CTS-300, and CTS-310.
- Professional Macro Assembler.
- Pascal is a true optimizing compiler with an extended implementation of the Pascal language. The extensions assist the application programmer in accessing P/OS system services and simplify application design. Extensions include ISAM (indexed sequential-access method), separately compiled procedures, sets of up to 256 elements, 31 character identifiers, FIND and LOCATE I/O procedures, and an OTHERWISE clause for the CASE statement.
- C is available from Whitesmiths Ltd.
I came across a sale on eBay that indicated an optional VAX card could be added to the PRO. It was marked as a Microvax II Proto 54-16707 CTI card. Lee Gleason purchased the cards and was kind enough to post pictures of them on his blog page. I retrieved the images form the page, cropped the, increased the contrast so the details are clearer. In DEC's "MicroVAX Business Plan" of December 1983 a reference is made to the "Meteor" project. This was a strategy for attaching a VAX card to the PRO380 computer as a CTI bus option.
"Meteor is Digital's first single-user MicroVAX product. Developed within Low End Engineering, the product is positioned as a strong competitor in the low end, technical/scientific and the high end office/business graphics workstation market. Meteor should be an effective follow-on product to the Professional Series and high end VAX/Seahorse workstations. Although not a replacement product per se, Meteor represents a clear migration path for PRO users upward in functionality, and for VAX Workstation applications downward to a lower cost, single user design."
This is the VAX softcard that was meant for the PRO380. As I understand it, it was never commercialized, but would have added the VAX 32 bit processor capability to the Professional desktop line. This would have made a great VMS software development platform.
VAX CPU Soft Card Top View
Underside View
The memory board is meant to attach to the VAX softcard. You can see the pins on the left side of the card and the accompanying connector where the memory card fits into. Similar to how the PRO series memory cards are atached to the system board.
VAX Soft Card Memory Top View
Underside View
DEC also manufactured an 8086 processor board produced for the Professional series. It was a self-contained card with processor and memory.
8086 Soft Card
Summary
The Digital Professional Series
family was designed to meet the needs
of the modern business organization.
Whether the need was for desktop computing
power, personal computer
clusters, or system-to-system communications,
the Professional series offered
functionality with ease of use.
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.