TUBLAT – A Homebrew MicroVAX I

The MicroVAX I.
The first MicroVAX and the slowest VAX ever (around 0.25VUPS).

This buid is based on a Corsair iCUE 7000X RGB black enclosure.
The MicroVAX I proved to be a difficult and limited machine, even before mentioning its eye-watering slowness.
A cold boot of VMS 5.4 plus Multinet takes 11 minutes.


Parts used in this build:

  • MicroVAX I CPU (M7135 + M7136)
  • MSV11-P (M8067) 512KB QBUS MOS MEMORY (two boards)
  • National Semiconductor NS23C 1MB QBUS MOS MEMORY (two boards)
  • RQDX3 (M7555) QBUS MSCP MFM/RLL Hard Disk/Floppy controller
  • DHQ11 (M3107) 8-port serial asynchronous line interface (eight RS232 ports)
  • DELQA (M7516) 10BaseT (10MBPS) Ethernet Controller
  • TDK/Lambda LS200-5/L (200W 5V 40A switching power supply)
  • XP Power VCS50US12 switching power supply (12V, 50W)
  • Custom MicroVAX II combo panel board (github project page)
  • Custom “VT100” ASCII terminal board (github project page)
  • Eyoyo S501H 5 inch LCD Monitor, 800×480
  • Custom board for generating the POK and DCOK signals (originally part of the H7864-C project)
  • DREM MFM/RLL emulator, emulating a single RD54 hard drive
  • GOTEK floppy drive emulator, emulating a RX33 floppy drive
  • Lots of other bits and pieces, wire, screws, spacers, termnial blocks, connectors and flat cables


The most modern operating system that would run as-is, more ore less, on the MicroVAX I was discovered to be VMS V5.4-1, dated November 1990. More modern operating systems may work, but at 2.5MB RAM and limited space (159MB on an emulated RD54), and the need for a networked machine, I doubt it is desireable or indeed possible.

Multinet 3.2D installed, it provides TELNET, FTP, name services and routing which is all that is needed.