TARZAN – a Homebrew MicroVAX II


The MicroVAX II enclosure chosen had to follow these guidelines:

  1. Be safe, so it would be difficult to poke hands and fingers in it causing equipment damage or personal injury
  2. Be transparent, so anyone can clearly see what’s inside
  3. Be large, so that assembly and maintenance is not a pain
  4. Be QUIET, so that the computer can be comfortably run in a living room, 24/7

The enclosure chosen was a Thermaltake “Level 20 HT Snow Edition”, a huge desktop/floor enclosure with four tempered glass windows, which has plenty of room for, well, anything really.

It has ventilation grills on the bottom, top and rear, and also along the vertical front supports.

A modular design, it was very easy to remove unnecessary bits, like the hard drive cage and various supports intended for ATX motherboards, water cooling radiators etc., and it was left nearly empty.

Hardware components

Other bits of hardware



To keep the MicroVAX quiet, several low-RPM, low noise fans were chosen. All the externally-facing fans are mounted so that they suck hot air out of the enclosure.

To increase the “blinkenlights” effect, the FUNCT/SEL SLU module was positioned inside the enclosure facing forward, so its display of CPU status is not hidden at the back. Also facing forward is the board carrying the DCOK, POK, 12VDC, and 5VDC indication LEDs.

The QBUS cage is also facing forward, to allow easy access to modules, and making various indicator LEDs on the QBUS boards visible from the front.

The four plastic feet were replaced with swivel caster wheels, to make moving the enclosure around a little easier. It weighs about 25Kg.

With the MicroVAX II powered, temperature rise of the internal surfaces of the enclosure is only around 4C above ambient, and the temperature rise of the CPU and FPU IC’s is around 13C-15C above ambient.

What’s installed on TARZAN the MicroVAX II ?

Disk storage: four “disk drives” reside on a 16GB SanDisk SD card. Each is 4GB In size, and they are visible in VAX/VMS as DUA0:, DUA1:, DUA2: and DUA3:.

UCX V4.2 , although not “officially supported” under VAX/VMS 7.3, appears to run OK, and it is the best option available, as the later TCP/IP stack “TCP/IP Services 5.x” requires a minimum of 24MB system memory to run. It is not possible on a MicroVAX II.

Why the name TARZAN ?

(From Abe’s Books): “Tarzan has many skills. He is a master of numerous languages and dialects, a physical freak in terms of strength and agility

A MicroVAX II, which is a 32-bit machine running at approximately 5MHz is exactly that – strong and agile, and indeed many [programming] languages reside within.