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D > DIGITAL EQUIPMENT CORPORATION > 300 Professional series   

Digital Equipment Corporation
300 Professional series

In conceiving the Professional 300 series, DEC designers decided that new machines must be able to perform several tasks at once, apply the same user interface, communicate efficiently and use the same software as Digital's popular microcomputers.

These personal computers were really desktop-sized versions of the PDP-11, one of Digital's popular minicomputer. Both models shared the PDP-11 instruction set and memory management. Both had an operating system based on Digital's RSX-11M+. For the user, this meant that software applications developped for more than 500,000 PDP-11 and VAX systems were candidat for easy migration to a desktop personal computer.

The members of DEC 300 Pro series were the 325 (two 5.25" disk drives, 400 KB each, and 1 expansion slot), the 350 (one 5.25" disk drive, 10 MB hard disk and 5 expansion slots) and the 380. The 325 and 350 used the F-11 CPU running at 13.33 MHz (the external clock actually ran at 26.66 MHz). The 380 used the J-11 CPU

About the number of colours: the three planes gave 8 colors at one time by referencing an 8 entry palette.Each entry in the palette could be programmed for one of 256 colors (by setting RGB values).

The internal card cage had space for up to 6 options total, and the base 350 system with EBO used four. The base 380 system used two. A Z80 card was available and allowed to use CP/M as the OS.

The operating systems which ran on it were P/OS (which was a variation of RSX), RT-11 and a variation of Unix called Venix. P/OS and Venix are freely available nowadays. RT-11 is still licensed software and is still being developed and maintained.

These systems were originally sold as standalone units, but were later incorporated into the VAX 8000 series as the system “Console”

Thanks to Megan Gentry, Former RT-11 Developer, who helped us 'debug' this page ;-)

Please consider donating your old computer / videogame system to or one of our partners from anywhere in the world (Europe, America, Asia, etc.).


The 300 Professional Series was, in truth, only "sort of" compatible with most of the PDP-11 line. Radically different interrupt hardware, and many other vital differences, meant that even the operating systems needed major modifications to work. Almost none of the software from the PDP-11 could run "as is". This left you what seemed like a fine machine with almost no software. For all of IBM''s faults they did a far better job here. Other things prevented this model series from catching on.

Tuesday 21st March 2023
Lawrence Shadai (USA)


NAME  300 Professional series
MANUFACTURER  Digital Equipment Corporation
TYPE  Professional Computer
YEAR  June 1982
KEYBOARD  Full-stroke 106 keys keyboard with 20 function keys, editing and numeric keypads
CPU  DCF-11 chipset (325/350) - Harris J-11 chipset (380)
SPEED  13.33 MHz. (325 - 350), 15 MHz. (380)
CO-PROCESSOR  MMU and FPA (belong to the DCF-11 chipset)
RAM  256 KB (up to 1 MB)
ROM  12 KB (contains power-up self test code, configuration & initialisation code and boot code)
TEXT MODES  80 x 24 / 132 x 24
GRAPHIC MODES  1024 x 256 dots.
SOUND  Although there wasn't a sound port, there was an option known as the Telephone Management System (TMS). It could be programmed to be used as a modem, but it also could be programmed to play and record sounds - one application turned it into essentially an answering machine - playing an outgoing message from a disk file, and recording incoming voice data to a file.
SIZE / WEIGHT  58(W) x 36(D) x 17(H) cm. (Mainframe)
I/O PORTS  Video output, Keyboard, Printer output (which could also be used for a debugging terminal), RS232, 6 expansion slots
BUILT IN MEDIA  325: 2 x 5.25 400 KB FDD
350: 2 x 5.25 400 KB FDD - 1 x 10 MB HDD
380: 2 x 5.25 400 KB FDD - 1 x 20 MB HDD
OS  P/OS, RT-11,, Venix
PRICE  Pro 325 : about US$8,000
Pro 350 : about US$10,000

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