Search Posts:

Digital DECmate VT278


Return to Threads

  Digital DECmate VT278 by Bill Degnan - 10/05/2017 08:10
Digital DECmate VT278
Digital DECmate VT278 Click image for larger view.

EK-VT278 Technical Description

Digital DECmate
The DECmate VT278 is a PDP 8 on a CPU / RAM board installed in a VT-100 chassis. Pictured here is the SETUP screen one sees upon successful boot. Click image for larger view.

Digital DECmate
This image shows the CPU card (left) and Comm port card (right side). Click image for larger view.

Digital DECmate
These are the RAM modules. Note that the rear RAM module was found to be defective and removed. The system should have 32K, I guess removing one RAM module will reduce to 28K, I have not determined yet, but the system will boot without the last RAM module installed. Click image for larger view.

Digital DECmate
Here is a close up of the RAM module removed from the CPU card. Note the missing pin. Click image for larger view.

Digital DECmate
After removing the bad RAM I was able to access terminal mode by pressing "4" from the SETUP screen. Click image for larger view.

Digital DECmate
This is the dual RX02 drive pedestal that came with the DECmate. I need to get cables and software. I don't know if the drives work. Click image for larger view.

More Photos

  Items Needed for DecMate by Bill Degnan - 10/17/2017 18:04
I need a 37pin to 25 pin drive cable, DECmate OS/8 disks in RX02 format, and a RAM module.

Tips on making a boot disk:

I have a catweasel it may be possible to use that to create disks See cw2dmk on this page:

Tips on replacing a RAM module:

I happen to have a 37pin to 25 pin cable that was used in a DEC environment, but it was split to connect to two "somethings" so I will need to check the pinouts from the manual and compare with the cable, hack it to work as a DECmate cable. Here is the pinout of a similar cable:

  Disk Images by Bill Degnan - 02/26/2019 00:18

Thanks Lou.

  OS/8 Disk created by Bill Degnan - 02/18/2020 22:06
DECMATE VT-278 rear ports
Pictured is the rear of the VT-278 with RX278 Floppy Drive Interface Connector (drive cable) attached. It's called a RX278 Floppy Drive Interface Connector cable, part number is RC26N-2L. Click image for larger view.

This weekend at the System Source computer museum I used their DECMATE VT278 to build a copy of the OS/8 boot disk for my system. Now that I have a known-working OS/8 disk, I need the cable. I checked page 23 of the ED-VT278-HR-001 Decmate System Architecture Manual for a pin-out to confirm that I don't have the correct cable on hand.

  Drive Cable Found, but... by Bill Degnan - 02/01/2021 01:17
Finally found a drive cable but alas the drive itself is not working. It responds to a request to boot from disk but the drive just "ding ding ding"'s...indicating probably a snapped or disconnected drive belt. I did make my own cable a while back and I got the same results, so at least I know my homemade cable is probably ok afterall.



Buy a Commodore Computer Poster

Popular Topics and FAQs

  • Commodore B Series Tips and Tricks
  • Aerocomp TRS 80 M 1 Expansion Unit DDC
  • Items Wanted
  • Lobo Max 80
  • Zenith Z-19-CN
  • Prototype PET 2001 photo
  • Using Toggle Switches to Analyze Memory
  • Commodore Disk Archive Project
  • PET 2001 Prototype at Gametronics 1977
  • Jim Butterfield Photo
  • IMSAI 8080 With Processor Tech. Cutter
  • Secrecy is the keystone of all tyranny
  • Cromemco System Three
  • Northstar Horizon - Boot Problem
  • Computer History and Restoration Links
  • Commodore BX-256-80 - 8088 Co-processor
  • S-100 board testing with Z-80 ICE
  • Donner 3500 - an early portable computer
  • Digital (DEC) PDP 11/05 NC Assembly
  • Univac 1219 rescue
  • Fido BBS listing node list 6-13-1986
  • PDP 8e
  • MITS 88-2 SIO (2SIO) for BASIC
  • Visual Technology Inc Model 1050
  • Amiga 2500 Restoration
  • The Evolution Of IBM Computers
  • Replacement teletype print hammer head
  • Archiving and Copying Software 101
  • Computers Built 1940 - 1950
  • CBM B-520 (a.k.a B256-80 or B500 256)
  • RCA COSMAC Microkit
  • Commodore 64K C-116 Mods
  • MITS 8800b Turnmon 9600 baud
  • Catweasel, 8in and 5 1/4
  • Raspberry Pi as Gateway to Internet
  • Digital PDP11 late 1969 early 1970
  • PDP 11/40 72 inch cabinet model
  • PDP 11/40 Industrial 11 model
  • Digitial MicroVAX 3100 30 System
  • Digital VAX 4000-200
  • Commodore 64 / 1541 DRIVEKNOCK
  • Booting the System Using RL02 drive
  • PACS: Reflections by Kathleen Mauchly
  • Tele-Graphic Computer Systems Inc.
  • Commodore B Series SID Jukebox?
  • Installing Core into PDP 11/40
  • Setting Up OpenVMS 7.1 DNS CLERK
  • Felt-Tarrant Comptometer Model J
  • NextStation Color
  • Digital Rainbow (PC100-B2)
  • 1970 Compusad Compulogical Tutor
  • Archiving Papertapes Using DSI NC 2400
  • 1976 P.C.C. Features the MAI JOLT 6502
  • 1961 Beckman DEXTIR Computer
  • UNIVAC 1 and UNIVAC File Computer 1
  • Past Issues:

    BASIS 108

    This image was selected at random from the archive. Click image for more photos and files from this set.