If you lived through the ’70s or ’80s, you probably remember a time when technology was big. TVs, with their cathode ray tubes, were monstrous. Amplifiers and hi-fis were heavy, bulky, expensive things. And computers… computers were really large. Case in point: The IBM hard drive pictured above, which weighs in at 38.5kg (85lbs) and stores a grand total of between 1 and 2 gigabytes.

This drive, which originates from around 1989, would’ve been teamed up with a number of other drives and slotted into a IBM 3390 Direct Access Storage Device (DASD) — a floor-to-ceiling server rack. One IBM 3390 model was capable of storing up to six drives, for a total capacity of 22.7GB. A complete IBM 3390 system had a data transfer rate of 4.2MB/sec, with an average seek time of 12.5 milliseconds. The platters probably span at around 2,500-3,000 RPM.

While it’s hard to put an exact price on a single drive, it would’ve cost somewhere in the region of $50,000 to $100,000 in 1989 — or about twice that, in today’s money. That’s around $50,000 per gigabyte — or one million times more expensive than today’s hard disk drives, which are currently priced at around five cents per gig.

With the background out of the way, I give you EEVblog’s teardown of the the hard drive. The video is rather long, so you might want to around the 8-minute mark for the case opening; the 15-minute mark for spindle motor; 20 minutes for the hard drive heads; and 33 minutes to see the head actuators in motion.

Back in the ’80s and ’90s, the IBM 3390 DASD was the pinnacle of reliable, online (as opposed to offline tapes) storage. EEVblog’s hard drive was sourced from a bank, where it would’ve stored recent transactions until they were backed up to tapes. In the ’80s and ’90s it would’ve been quite common to find systems like these in the vaults of banks, and large corporations and institutions.

It’s worth noting that this drive isn’t big just because it’s old. In 1989, 2.5-, 3.5- and 5.25-inch hard drives already existed — but their capacities were measured in megabytes. The IBM 3390 had a large capacity, but it was primarily designed for reliability — and in the ’80s that meant going large (the platters are 11 inches across in this case). If you watch through the entire teardown, you will see that the hard drive’s only silicon chip is a tiny chip that acts as a signal amplifier. If you look closely, you’ll see a nozzle on the drive’s exterior that was used to pump the enclosure full of pressurized halon, increasing reliability. EEVblog says that these IBM drives were so reliable (and so expensive) that many institutions carried on using them well into the ’90s.

At this point, you should check out our history of computer storage. It’s amazing how hard drives were one of the most recent advances in non-volatile storage, and yet the fundamental technology has remained almost unchanged for 40 or 50 years. If you took the IBM 3390 drive and simply scaled it down a few hundred times, it would look virtually identical to a modern hard drive.

Now read: How a hard drive works