Category: MicroVAX I

With two screws removed from the rear of the case the computer can be removed from its skin. The skin itself is very heavy and once gone the computer can be easily lifted on to a bench by two people.

The front panel comes off with the removal of several screws. The drives are on skids and can be released by pressing on the handles at the bottom of the case.

Two screws retain the back panel. Two ground leads need to be disconnected for the panel to be free and the rack to be revealed.

I pulled each of the cards just for a photo and to confirm the ID. The ejection handles are solid and require a fair bit of effort to operate. They have to be positioned correctly when the cards are inserted into the rack. The levers pull the cards home.

The machine has:

• An KA610/KD32 CPU consisting of two cards M7135 Data Path Module and M7136 Memory Controller.
• Memory modules including 1x M7551 MSV11-QA 1MB Memory Module and 2x M8067 MSV11-PL
• M8639 RQDX1 Disk Controller – not sure of version. Could also be RQDX2.

The only external I/O is the console serial port so this is very much a standalone system. If it shows promise then i could acquire some additional cards. No point at this stage.

A few screws and some cable disconnections and the power supply is out. There are 4 RIFA line filtering capacitors and they are cracked as expected. There are no obvious issues with any other companents.

That’s it until the replacement arrive.

• MicroVAX I Disassembly
• DEC MicroVAX I

The subject of this site is microcomputers and although this unit has micro in the title it is actually a minicomputer. Why get hung up on consistency?

This machine is a recent arrival and so far it has not even been powered up. It belonged to a gentleman who developed security software for the VMS operating system although i suspect that this unit was possibly a nostalgic purchase rather than being a machine that was used by him for real work.

Curiously it came with a bunch of tapes and a few high density 5.25″ disks none of which can be read by this machine. This, together with a shipping label that was on the machine dated 2001 is why i think this machine was a nostalgic purchase. Perhaps more will be revealed if it ever boots.

The MicroVAX I was released in 1984 and was quickly superseded by the MicroVAX II which is a more common and more useable model.

The MicroVAX series was a more compact and less capable derivative of the VAX computers that i used as a student of Adelaide Uni in the early eighties, speaking of nostalgia.

The MicroVAX I uses a Q-bus backplane which was also used in some DEC PDP computers. The CPU consists of two Q-bus cards. The MicroVAX I typically shipped with 1MB memory. This one has a dual floppy disk drive and a 30MB hard disk and would therefore have a floppy/hard disk controller.

With the only wired I/O being a serial line for a console terminal this unit is truly standalone. Additional Q-bus cards can be added for many other functions but i imagine they won’t be easy to find.

There are RIFA line filter capacitors inside, so there is work to be done before power can be applied.