DECmate I
The DECmate I is a word-processing computer made by Digital Equipment Corporation (DEC) from 1980 to 1984. DEC sold it simply as the DECmate; the "I" was added after the DECmate II appeared. The machine is a VT278 video terminal: a VT100-style case holding a CPU board built round the Harris 6120, a single-chip implementation of the 12-bit PDP-8 instruction set, with RX02 8-inch diskette drives in a separate unit.[1][2]
.jpg) | |
| A DECmate I with the word-processing keyboard | |
| Specifications | |
|---|---|
| Manufacturer | Digital Equipment Corporation |
| Type | Word-processing workstation and PDP-8 compatible computer |
| Released | 1980[1] |
| Discontinued | 1984[1] |
| CPU | Harris 6120 (12-bit, PDP-8 instruction set)[2] |
| Memory | 32K 12-bit words main memory[3] |
| Storage | RX02 dual 8-inch diskette drive (separate unit); optional RL02 cartridge disks[2][4] |
| Display | 12-inch monochrome CRT, 24 × 80 or 14 × 132 characters[4] |
| Sound | — |
| Weight | 13.6 kg (30 lb) terminal; 2.0 kg (4.5 lb) keyboard[4] |
| OS / Firmware | WPS-8/278, COS-310, OS/278[5] |
| Successor | DECmate II |
| Model no. | VT278 |
History
editThe DECmate I replaced the VT78, which had put a PDP-8 processor inside a VT52 terminal. Douglas Jones's PDP-8 FAQ gives its introduction as 1980 and its withdrawal as 1984, when it was phased out in favour of the DECmate II.[1] DEC's own manuals for it date from 1981: the DECmate Technical Description (March 1981), the DECmate System Architecture Manual (June 1981) and the VT278 field maintenance print set (May 1981).[2][4][6]
The FAQ describes the DECmate I as a closed system. Its options were a second RX02 (or an RX01), the DP278-A and DP278-B communications boards, and the RL278 controller for one to four RL02 cartridge disk drives.[1]
Hardware
editThe VT278 contains the CPU board, the keyboard interface, the video monitor board and the power supply. DEC's block diagram shows the 6120 microprocessor, 32K words of main memory, a 100 Hz real-time clock, the CRT controller and the keyboard controller on the CPU board.[2]
The 6120 runs user programs from main memory and uses a second 32K-word address space, called control panel memory, for self-test, terminal emulation, the floppy bootstrap, the display buffer and the CRT control registers.[2] The DECmate II specification compares the two machines: the DECmate I runs its 6120 at 5 MHz and has 4K words of fitted control memory, against 8/4 MHz and 32K words on the DECmate II.[7]
| Assembly | Part | Notes |
|---|---|---|
| CPU module | M8436 | 6120, memory, CRT, keyboard, printer and diskette control |
| Communications adapter | M8437 | DP278 option |
| I/O connector board | 5414322 | Carries the 72-pin module connectors |
| Keyboard | 70-14653 assembly, 5413404 board | Keycap sets for word processing and several languages |
| Monitor board | 5414131 | Drawn as the VT100 monitor board |
| Power supply | H7836-A (120 V), H7836-B (220 V) | +5 V 2.5 A, +12 V 2 A, −12 V 0.25 A |
The keyboard is joined to the CPU board by a 3-wire cable. Two wires carry +12 V and ground for the keyboard logic; the third is a bidirectional serial line.[3] The power supply takes 120 V or 220/240 V, selected by a slide switch on the rear panel, and a second switch selects 50 Hz or 60 Hz.[3]
Display
editThe display is 24 rows of 80 characters or 14 rows of 132. Each character can be given increased intensity, underlining, blink or reverse video.[3] The screen brightness is set from the keyboard in SET-UP mode, in 16 steps.[8]
Storage
editA 37-pin connector at the rear of the VT278 takes one or two dual diskette drives.[3] Each RX02 diskette holds 256,256 12-bit words formatted on 77 tracks.[4] The printer port is a 25-pin connector; it starts at 9600 baud and can be set from 50 to 19,200 baud under program control.[3]
Rear panel
edit
The rear panel carries the floppy disk, printer, keyboard, COMM 0, COMM 1 and cartridge disk connectors, the POWER O.K. and CPU O.K. indicators, the main fuse, the power switch, and the line frequency and voltage selector switches beside the power cord connector.[9] PWR OK lights when the power supply passes its tests; CPU OK blinks once a second when the basic tests pass.[10]
Known faults
edit- Randy Hick's notes on the VT100 monitor board, which the VT278 also uses, give C439 and CR408 as a common cause of a blank white raster. See DECmate I Troubleshooting Guide.[11]
- A failed self-test is reported on the keyboard LEDs and the CPU OK indicator. DEC's table of LED patterns is in the troubleshooting guide.[8]
Documentation
editThe DEC manuals for the DECmate I are hosted here and described on DECmate I Documentation.
- DECmate Technical Description, EK-VT278-TD-001: File:DECmate Technical Description (EK-VT278-TD-001).pdf
- DECmate System Architecture Manual, EK-VT278-HR-001: File:DECmate System Architecture Manual (EK-VT278-HR-001).pdf
- VT278 field maintenance print set, MP-00900: File:DECmate VT278 Field Maintenance Print Set (MP00900).pdf
- DECmate Owner's Guide, AA-K330E-TA: File:DECmate Owner's Guide (AA-K330E-TA).pdf
Related pages
editReferences
edit- ↑ 1.0 1.1 1.2 1.3 1.4 Douglas W. Jones, "PDP-8 Summary of Models and Options", alt.sys.pdp8 FAQ, posted 8 June 2001, section "What is a DECmate I?", faqs.org. Introduction 1980, withdrawal 1984, VT278 name, 6120 in a VT100 box, RX02 in the pedestal, options, operating systems.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Digital Equipment Corporation, DECmate Technical Description, EK-VT278-TD-001, March 1981, pp. 1-1 to 1-2 (File:DECmate Technical Description (EK-VT278-TD-001).pdf). System overview, block diagram, CPU board, control panel memory.
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 DEC, DECmate Technical Description, EK-VT278-TD-001, pp. 1-3 to 1-4. Main memory, CRT control, real-time clock, diskette and printer ports, keyboard cable, power supply input switches, options.
- ↑ 4.0 4.1 4.2 4.3 4.4 Digital Equipment Corporation, DECmate System Architecture Manual, EK-VT278-HR-001, June 1981, pp. 1-4 to 1-6 (File:DECmate System Architecture Manual (EK-VT278-HR-001).pdf). Specifications of the VT278, RX02 and RL02.
- ↑ DEC, DECmate System Architecture Manual, EK-VT278-HR-001, p. 1-3. The three DEC operating systems for the DECmate: WPS 8/278, COS-310 and OS/278.
- ↑ 6.0 6.1 Digital Equipment Corporation, VT278 field maintenance print set, MP-00900, May 1981 (File:DECmate VT278 Field Maintenance Print Set (MP00900).pdf). Drawing directory (PDF p. 4), terminal sub-assembly parts list with the H7836 ratings (PDF p. 23), module parts lists.
- ↑ Digital Equipment Corporation, DECmate II Specification, revision 4, 18 January 1983, section 2, "System Components", bitsavers.org. CPU speed and control memory of the DECmate I and DECmate II compared.
- ↑ 8.0 8.1 DEC, DECmate System Architecture Manual, EK-VT278-HR-001, p. 3-6. Table 3-1 General Self-Test Summary; SET-UP brightness control.
- ↑ DEC, DECmate System Architecture Manual, EK-VT278-HR-001, p. 3-3, Figure 3-2, "VT278 Rear Panel With I/O Cover Removed".
- ↑ DEC, DECmate System Architecture Manual, EK-VT278-HR-001, pp. 3-4 to 3-5. Rear panel controls and LED indicators; power and CPU OK tests.
- ↑ Randy Hick, "VT100 trouble analysis of video monitor board", text file hosted at bitsavers.org. Community repair notes for the VT100 monitor board.