Taking a Vintage DEC Drive for a Spin

Hard disks, SD cards, and the like are so compact and inexpensive these days that it is easy to take them for granted. Got a couple of terabytes of data that you need to store somewhere? That is nothing that 15 bucks and a tiny card the size of your fingernail can’t take care of for you. But it wasn’t always this way, of course. Just a few decades back, the storage capacity in megabytes and the weight in pounds of a hard disk drive was pretty close to the same.

Former Microsoft engineer Dave Plummer, best known for his work on Space Cadet Pinball and Windows Task Manager, recently acquired a massive vintage disk drive of this sort. This DEC RA82, which weighs in at 200 pounds and can only store 622MB of data, may not be very practical for real world use today. But it is the perfect complement to his DEC PDP-11/73 computer. So Plummer decided to whip it into shape and use it to run a Unix operating system on the vintage machine.

Nobody’s eyes are going to pop out when looking over the specs for the RA82 today, but at the time, it was really high-end equipment. The magnetic platters spin at 3,600 RPM and have an average rotational latency of about 8.3 milliseconds. The disk also comes equipped with not one, but two microprocessors of its own. One tracks the mechanical aspects of the drive, including head loading, servo positioning, and spindle control. The other is dedicated to managing communications with the host computer.

The RA82 uses something called the Standard Disk Interconnect to interface with computers. But despite the name, it is anything but standard today. Fortunately, Plummer got all of the required cabling along with the drive, and some time spent with a copy of the manual helped him to get it all wired up correctly.

Before loading Unix, the disk first needed a low-level formatting that prepares the raw sectors for data storage. That was followed by the creation of a partition table to specify volumes, then creating a file system on each volume. From there, a very complicated process was needed to get Unix loaded on the disk in a complete and bootable state, but after a few days, Plummer had all of the details worked out.

The first boot sounded something like a jet taking off, but that is just part of this classic disk’s charm. Not only is an exercise like this a great education in computer storage technologies, but the result is also beautiful and a perfect, era-appropriate complement to a DEC PDP-11/73. Be sure to watch the end of the video to see the RA82 start up before the computer boots to Unix from it.