The MicroVAX II enclosure chosen had to follow these guidelines:
Be safe, so it would be difficult to poke hands and fingers in it causing equipment damage or personal injury
Be transparent, so anyone can clearly see what’s inside
Be large, so that assembly and maintenance is not a pain
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
A H9278-A QBUS-22 8-slot backplane (DEC P/N 5015964), populated with
A DHV11 eight-port, asynchronous, DMA multiplexer (M3104)
A custom “Patch Panel” (console FUNCT SEL/SLU Module), a direct replacement for DEC P/N 5416744-0-1 or 5016743-01 (CK-KA630)
A custom “TOY (Time of Year)” board, holding a 14500-type Lithium rechargeable battery and charging circuitry to keep the server’s internal clock alive when not powered
A custom side panel board, which includes
A Direct replacement for the DELQA cab kit (70-22786-01)
Two DHV11 cab kits (similar to H3173-A, CK-DHV11-XX)
Space for a FUNCT/SEL SLU Module (unused)
Drivers for external LEDs - unused
A custom board for generating the QBUS BPOK (AC Power OK) and BDCOK (DC Power OK) signals required for the KA630 operation
OMRON power supply p/n S8FS-G15005CD, for 5V/21A (100 Watts)
OMRON power supply p/n S8FS-G05012CD, for 12V/4.3A supply (50 Watts)
An HP EtherTwist MAU (AUI Ethernet (DB15) 10BasetT to UTPRJ45) adaptor, p/n 28685A
Other bits of hardware
The enclosure’s Power LED and HDD LED were tied to the BDCOK and SRUN signals, respectively
The enclosure’s POWER pushbutton was tied to the BDCOK signal, so that it could be used as a hard RESET button
An old PC ATX power supply was scavenged for its rear panel, which holds the IEC AC cord power entry socket and the on/off switch
Two Tyco 5-1542004-4 heatsinks were attached to the FPU and the CPU ICs on the KA630 board. These 3-fin heatsinks are intended for 21mm BGA components, but they attach very well to the 21.6mm FPU and CPU heatsinks. No thermal grease or messy installation required.
Flat cables: 10-conductor and 20-conductor for the SLU, 20-conductor for the DELQA Ethernet cab kit, 40-condctor for the DHV11 cab kit, 50-conductor for the SCSI interface
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.
A Noctua AN-A20PWM 20cm fan directed at the QBUS cage
A Noctua NF-S12A CH.BK.S 1200ROM Chromax Black Swap fan, positioned directly above the KA630’s CPU and FPU IC’s.
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 ?
OpenVMS VAX 7.3 - this is the latest and final distribution of VMS for VAXen. VAX/VMS 5.5-1 was considered, but it is too old to support UCX 4.2, and would not run desired applications like a HTTP server.
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.
