Olfs Computer Zoo - MicroVAX 3300

DEC? Thats the VMS people, right?

Exactly. The VAX ist the peak of the CISC architecture, and runs happily with VMS. The VAXen family is widespread, from desktop machines to multi-rack monsters. The MicroVAX ist a later model and belongs - even at sight - to the smaler VAXen.

While the CPUs of the earlier models - like the calssic VAX 11/780 filled multiple boards, the VAX architecture has been cramed on a chip in a CMOS implementation for the MicroVAXen. The chip called CVAX runs at 10MHz in the 3300 and as 1kB(!) cache attached. The memory is luxuriosly equipped with 4MB - VAX machine code is extremely dense.

To be able to realize the CVAX chip with the then contemporary technology, DEC utilized a trick: The CPU implements only the most common instructions of the VAX instruction set - the rest triggers a trap, and is implemented in software.

Square, nice and handy.

The MicroVAX 3300 and a VT-320

Even mechanicaly the 3300 stands out from the masses - which coputer looks like a flower stand. The base of the case is nearly square, with castors on the bottom. With about three feet height, you could easily pace a flower pot or a vase atop.

But a terminal comes in nicely - my VT-320 gets along well with the VAX. Meanwile I got hold of a keyboard with US layout, what eases up things noticably.

The drive are located On the upper front behind the cover. To the left are two 300MB DSSI disks on thick rubber mounts. DSSI is a early, incompatible variant of SCSI. They are 5.25" devices in half height. There is space for one more.

The front panel has an error LED, a write protect switch (with LED) and a ready switch (with LED) for each of the drives possible. Below are the Restart/Run and teh Halt push-button plus teh power LED.

The front panel can be covered with a protective door of semi-transparent perspex, through wich the LEDs glow.

Compaq Tape? - CompacTape!

Top right you see the CompacTape drive. These things are the grand-grandfathers of the modern DLT (Digital Linear Tape) drives. Full 90MB are packed on the tapes. The Media looks exactly like DLT tapes, so the mechanical specs did'nt change.

CompacTapes

The tape cartridge technologie is inventive. To save the room the empty reel would take up, only the would up tape is in the cartride. In front is an eyelet for tearing the tape out and threads it into the mechanics. Since this is afully complicated, you ougth to obey the right sequence when changing tapes: Press button, wait for LED to go dark, open lock, remove cartride, insert new one, close lock, press button, wait for LED to light steady, done.

VMS is different

Only VMS is possible as an operating system for this VAX at this time. NetBSD does not support the DSSI disks an the "classic" V7 binaries from DEC/Compaq/HP only like "classic" Hardware, in the directionof a VAX 11/750. Thats hard for an Unix guy, because VMS is different ... sigh.

For instance I was not able to shut down the machine cleanly in the beginning, also I already had found shutdown.com. How could I know that its a DCL script and thus has to be called as @shutdown. Meanwhile I found the docs on the net and borrowed a few paper manuals.

Besides, VMS is extremely chatty. Options are prefixed with '/' (where have I seen this before?). This gives something like:

BACKUP/VERIFY/LOG *.LIS MFA0:LIST.BCK

Saves all files of type LIS to drive MFA0 under the name LIST.BCK, with verify and log listing. Or, short gtar cvWf /dev/rmt0 *.lis

On the other hand VMS can do several intersting things. The filesystem can manage different versions of each file inherently. The security meassures are manifold and sophisticated, as well as the accounting system.

It even has a TCP/IP Stack, which is configured different, but meanwhile the machine is fully integrated in the network.