The first hard drive, the IBM 350 Disk Storage Unit, made its debut in 1956 when IBM introduced the RAMAC 305 vacuum tube computer system. RAMAC stood for “Random Access Method of Accounting and Control”, which gives you an idea of the market IBM was targeting at the time. Over 1,000 RAMACs were produced in total between 1956 and 1961.
The RAMAC allowed transactions to be recorded as they happened and to be applied to multiple accounts simultaneously. In addition, you could randomly access any of those records instead of having to read sequentially through vast amounts of data. This helped even out processing loads, so heavy peak times were a thing of the past. Such real-time computing was quite revolutionary at that time.
Only large corporations and government agencies with a significant amount of money could afford the RAMAC 305, which could be leased for $3,200 a month. The entire system was comprised of several components:
- 305 Processing Unit
- 370 Printer
- 323 Card Punch
- 380 Console
- 340 Power Supply
- 350 Disk Storage Unit
Altogether, the entire RAMAC system weighed over a ton and had to be moved with forklifts (imagine those shipping charges). It took up an inordinate amount of space, basically an entire room.
Originally the 305 included one Disk Storage Unit, but within two years of its debut, an optional second Disk Storage Unit could be added. An additional arm per Disk Storage Unit was also added.
The primary component of the 350 Disk Storage Unit was a magnetic disk memory unit that was accessed via pneumatic and electronic controls. The 24” disks, of which there were 50, were arranged vertically. Data could be written to 100 tracks on either side of each disk. The disks spun at 1200 RPM.
The access arm moved vertically to select the appropriate disk, then horizontally to select the appropriate track. There were two read/write heads at the end of the arm, one to access the top of the disk and one to access the bottom of the disk. The distance between the head and the disk was 800 microinches.
The data transfer rate was 8,800 characters per second.
In terms of capacity, the 50 disks each had 50,000 sectors. Each sector held 100 characters, making the full capacity 5 million characters, or 5 MB. So basically it would take an entire 350 disk drive to hold a 5 minute MP3 file.
The form factor was astonishing compared to the external hard drives of today. Fully assembled, the 350 was 60” x 68” x 29” (picture an oversized washing machine).
Seek time was around 600 milliseconds. Data was recorded at a max of 100 bits/inch.
When you think about the fact that it’s been a little over 50 years since the IBM 350 Disk Storage Unit was manufactured, it boggles the mind. You can carry around 2 terabytes of data in your pocket on a device that’s about the size of a deck of cards!
Below is an info-graphic that compares the IBM 350 with hard drives of today. It’s amazing how far we’ve come since that first hard drive.