Today a memory card smaller than a fingernail can carry terabytes of data. In 1956 the first hard drive was the size of a large refrigerator, weighed about a ton, and held less data than a single high-resolution photo would take today.
Its name was the IBM 350, and it changed the course of computing history. Because for the first time a computer could reach recorded data directly, not sequentially. If you don't wait when you open a file or search in an app today, the root of that lies in this giant cabinet.
50 disks, 1,200 revolutions per minute
The IBM 350 disk storage unit was introduced in September 1956 as part of the IBM 305 RAMAC computer system. Sources differ on the exact day: Wikipedia gives September 14, while ASME's engineering heritage record gives September 4. RAMAC stood for "Random Access Method of Accounting and Control".
At the heart of the device were iron oxide-coated disks 24 inches (61 cm) in diameter. Most sources say 50 disks. Wikipedia writes 52 disks, with 100 of their surfaces used for recording, so the figure varies with how you count. The disks spun at 1,200 revolutions per minute, and an access arm went to the right disk and the right tracks to read the data.
"Random access" was revolutionary for those years. Until then business data was usually read sequentially from magnetic tape or punched cards. With the IBM 350 it became possible to go straight to the record you wanted.
According to heise, development of the project had begun in 1952. The disks were stacked only about 0.72 cm apart. Having an arm go to the right spot and read data among giant platters spinning at 1,200 rpm in such a narrow gap was a serious achievement for 1950s engineering.
3.75 MB: what does "5 million characters" mean?
The IBM 350's capacity was advertised as 5 million characters. But each character was stored with 6 bits. In today's 8-bit byte terms, that comes to about 3.75 MB. heise adds one more detail: although the theoretical capacity looks higher, parity and gap bits reduced the usable space, which is why the effective capacity is cited as about 3.75 MB. According to heise, data was kept in 50,000 blocks of 100 characters each.
The data transfer rate was 8,800 characters per second. At that speed, this entire article could be read in under a second. For the business world of 1956, this was a big relief compared with dealing with stacks of punched cards. The cabinet was about 152 cm long, 172 cm high and 74 cm wide.
A forklift, a cargo plane and a ton
Moving such a large machine was a job in itself. Wikipedia writes that the device weighed about a ton and was moved by forklift and often shipped in large cargo planes. heise gives the weight as "almost a ton" including the cooling system and recalls a photo of a RAMAC being unloaded from a DC-7 aircraft at Amsterdam Schiphol Airport in 1957.
That is the truth behind the "first hard drive moved by forklift" photos circulating online.
| IBM 350 (1956) | Today |
|---|---|
| About 3.75 MB | Drives holding terabytes of data |
| About 1 ton | SSDs that fit in your palm |
| 50 disks of 24 inches | A single small circuit board |
| Lease only | Memory cards sold at the store |
A short but deep mark
The first engineering prototype went in June 1956 to the Zellerbach Paper Company in San Francisco. According to Wikipedia, deliveries of series-production units began in November 1957. According to heise, production stopped in 1961 after more than a thousand units had been built. RAMAC was withdrawn from the market entirely in 1969.
A machine that weighed a ton, could only be leased and held a few megabytes may sound funny today. Even a single photo taken with a phone today often strains this capacity. But the idea of "direct, non-sequential access to data" stands at the foundation of every disk and every database we use.
Do you think that in 70 years we'll look at today's terabyte drives with the same smile?