Jump to content

Professional 350

From RetroTechCollection
Professional 350
DEC Professional 350 (Centre for Computing History)
Professional 350 system unit, model PC350-D
Specifications
ManufacturerDigital Equipment Corporation
TypePDP-11 compatible personal computer
Released1982[1]
CPUDEC F-11 chip set[2]
Memory128 KB RAM daughterboards (each upgradable to 512 KB); 3 MB maximum[3]
StorageRX50 dual 5.25-inch diskette drive (819 KB); RD50 (5 MB), RD51 (10 MB) or RD52 (32 MB) hard disk[2][4]
DisplayVR201 30.5 cm (12 in) monochrome monitor; bit-mapped graphics[2][5]
Sound—
PowerH7862 switching supply, 320 W[6]
Dimensions16.5 × 55.8 × 34.3 cm (6.5 × 22 × 14.3 in)[6]
Weight15.9 kg (35 lb) maximum[6]
OS / FirmwareP/OS[1]
SuccessorProfessional 380
Model no.PC350

The Professional 350 (PRO-350) is a personal computer based on the PDP-11 architecture, made by Digital Equipment Corporation (DEC) and introduced in 1982 with the Professional 325.[1] It uses DEC's F-11 chip set on a single system module, with a proprietary card cage bus, bit-mapped video, an RX50 diskette drive and an RD-series hard disk.[2][1] The 325 and 350 share the system module and differ in the number of option slots and in hard disk support; DEC's manuals describe both together.[7]

History

[edit | edit source]

DEC launched the Professional series in 1982 alongside the Rainbow 100 and DECmate II, with the same LK201 keyboard and RX50 drive, as its answer to the IBM PC; none of the three sold well.[1] The standard operating system was P/OS, a menu-driven derivative of RSX-11M; RT-11, Venix and 2.9BSD also ran on it. The faster Professional 380 followed in 1985.[1]

Hardware

[edit | edit source]
Professional 350 system module and card cage (DEC Figure 5-2)
Professional 350 system module with its card cage, battery and LED display (DEC, EK-PC300-V1-001, Figure 5-2)

The system module is a circuit board on a metal plate that slides in and out of the bottom of the enclosure. It carries the processor, memory control, the keyboard, printer and communications ports and a six-slot backplane for the CTI (Computing Terminal Interconnect) bus.[7][8] DEC's parts list calls the board the CT100 system module, 5415101, mounted with the card cage on the KDF11-C large system unit motherboard assembly.[9]

Professional 300 series differences (DEC Table 1-1)
Item 325 350
RX50 diskette drive Yes Yes
User option slots (diskette-based system) 1 3
RD hard disk No Yes
Hard disk operating system No Yes
Download over a network No Yes

[2]

In a diskette-based Professional 350, slots 1 and 2 hold the RX and RD disk controllers and three slots are left for options.[6] DEC's manual says cable restrictions require the hard disk controller to be in slot 1.[10] Video comes from a bit map video controller module, with an optional extended bit map module (EBO) in the slot next to it.[10] RAM is on plug-in daughterboards of 128 KB, upgradable to 512 KB, of which two can be fitted; the system module's 22-bit addressing reaches 4 MB, but DEC limited the system to 3 MB.[3]

The system module also has a battery-backed time-of-day clock with 50 bytes of battery-backed RAM.[8] The battery is a three-cell 3.75 V nickel-cadmium pack (DEC 12-19245-00) on connector J3, which the power supply charges at 10 mA while the computer is on.[9][11][12]

Power supply

[edit | edit source]

The H7862 switching supply sits at the top left of the chassis, with a front rocker switch, a rear 115/230 V selector and circuit breaker, and an exhaust fan that draws air through the whole system unit. It delivers +5.1 V at up to 20 A, +12.1 V at up to 8 A and −12 V at up to 1 A, and tells the processor through two signals, DCOK and POK, when the outputs and the mains are good.[13][14] The same supply is used throughout the Professional 300 series; its capacitor list is on Professional 325 Capacitor Replacement Guide.

Specifications

[edit | edit source]
Professional 350 specifications (DEC section 1.2)
Item Specification
Processor DEC F-11 chip set
Memory Addresses up to 3 MB
Video RS-170 compatible monochrome, bit-mapped graphics
Communications port RS-423, asynchronous or byte synchronous, up to 19.2 kbaud, with modem control
Printer port Serial, RS-423
Removable storage RX50 dual diskette drive, 819 KB, 96 tracks per inch
Fixed storage RD50 5 MB (170 ms access), RD51 10 MB (85 ms), RD52 32 MB (37.5 ms)
AC input 90–128 V or 174–256 V rms, 47–63 Hz, switch selectable
Line current 6 A at 115 V, 4 A at 230 V
Power consumption 320 W maximum

[2][6][4]

Self-test

[edit | edit source]

The self-test runs at every power-up. Four red LEDs on the back show its progress and turn off at the end, when the DIGITAL logo appears on the screen; a green LED shows that the system module is receiving DC power.[15] DEC's tables of the LED codes and corrective actions are on Professional 325 Troubleshooting Guide, and the codes, error numbers and faults particular to the 350 are on Professional 350 Troubleshooting Guide.

Known problems

[edit | edit source]
  • The nickel-cadmium clock battery leaks. One owner who removed the pack after years of storage still found the board damaged around the battery connector, with a dead clock chip and a nearby 74LS04; the machine reported errors 000020 and 000023.[16]
  • RX50 drives stick: a seized spindle, and a drive running at 293 r/min instead of 300, gave error code 330, "drive speed not in limit".[16]
  • The VR201 monitor suffers the same "cataracts" and ageing capacitors as on the Rainbow; one VCF member's VR201 lost vertical hold and then went black on a Professional 350.[17] See DECmate III Capacitor Replacement Guide for the VR201 capacitor list.

Documentation

[edit | edit source]

The hosted DEC documents are described on Professional 350 Documentation.

[edit | edit source]

References

[edit | edit source]
  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 "DEC Professional (computer)", Wikipedia, en.wikipedia.org, retrieved 2 October 2026. Introduction dates, launch with the Rainbow and DECmate II, operating systems.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 DEC, EK-PC300-V1-001, p. 1-3, Table 1-1 and section 1.2. System differences and specifications.
  3. ↑ 3.0 3.1 DEC, EK-PC300-V1-001, p. 5-3. Memory daughterboards and addressing.
  4. ↑ 4.0 4.1 DEC, EK-PC300-V1-001, pp. 1-6 to 1-7. RD50, RD51 and RD52 hard disk specifications.
  5. ↑ DEC, EK-PC300-V1-001, p. 1-5. Monochrome monitor and RX50 specifications.
  6. ↑ 6.0 6.1 6.2 6.3 6.4 DEC, EK-PC300-V1-001, p. 1-4. Expansion, power and physical specifications.
  7. ↑ 7.0 7.1 Digital Equipment Corporation, Professional 300 Series Technical Manual, Volume 1: Kernel System, EK-PC300-V1-001, June 1985, p. 1-2 (File:Professional 300 Series Technical Manual Volume 1 (EK-PC300-V1-001).pdf). System unit components; the 325 and 350 identical except as noted.
  8. ↑ 8.0 8.1 DEC, EK-PC300-V1-001, p. 5-4. System module features and physical description.
  9. ↑ 9.0 9.1 Digital Equipment Corporation, PC350 field maintenance print set, MP-01394-00, KDF11-C large system unit motherboard parts list (PDF p. 11) (File:Professional 350 PC350 Field Maintenance Print Set (MP-01394-00).pdf). CT100 system module 5415101-00 and "BATTERY, 3CELL 3.75V .18MA NICAD", 12-19245-00.
  10. ↑ 10.0 10.1 DEC, EK-PC300-V1-001, pp. 2-6 to 2-7. Module installation: extended bit map module beside the video controller, hard disk controller in slot 1.
  11. ↑ DEC, EK-PC300-V1-001, p. 5-55. Battery charging at 10 mA and clock retention.
  12. ↑ DEC, EK-PC300-V1-001, p. 5-130, Table 5-23, J3 battery back-up connector.
  13. ↑ DEC, EK-PC300-V1-001, pp. 10-1 to 10-3. H7862 power supply description.
  14. ↑ DEC, EK-PC300-V1-001, p. 10-11, section 10.6.2. Electrical specifications.
  15. ↑ DEC, EK-PC300-V1-001, p. 3-2. Indicators 1 to 4 and the DC indicator.
  16. ↑ 16.0 16.1 "Pro 350 revival", Vintage Computer Federation forum, thread started 18 July 2025, forum.vcfed.org. Battery damage, RTC repair and RX50 speed fault reported by the owner.
  17. ↑ "Fixing a dead VR-201", Vintage Computer Federation forum, thread started 12 April 2023, forum.vcfed.org.
Retrieved from "https://retrotechwiki.com/index.php?title=Professional_350&oldid=24449"