The Sagacious Iconoclast: 50th Anniversary of Computer Disk Drive Memory

First Computer Disk Drive

The IBM 350 RAMAC

50th Anniversary

2006-09-13

The first computer memory disk drive, the IBM 350 RAMAC (Random Access Method of Accounting and Control), was released fifty years ago today, on September 13, 1956, as a component of the IBM 305 computer. The 305 was one of the last vacuum tube computers that IBM built.

The first unit was shipped to Crown Zellerbach, which got the RAMAC because the company delivered a lot of computer card stock to IBM.

In 2006, about 450 million to 460 million drives will leave factories, according to Disk/Trend.

According to the Electrical Engineering Times^[1]:

The RAMAC marked the birth of an industry with a history as colorful as any in electronics, punctuated by such events as an unprecedented mass exodus from IBM, two major lawsuits that ended in a draw, a fatal strategic misstep stemming from company politics and even a country-club murder. Along the way came sensational boosts in storage capacity and access speeds along with amazing reductions in size.
IBM's RAMAC disk drive was a momentous achievement. So one might assume that it consumed a great deal of corporate enthusiasm and top-management support. Well, it didn't. Instead, geography and the relatively primitive state of transportation were the factors that mainly contributed to its success.
San Jose, California, a relatively small town in the '50s, was 12 hours away by plane from IBM headquarters on the East Coast, a tough trip for busy executives. The difficulty kept visits down, so the research team in San Jose -- led by Reynold B. Johnson, who turned over responsibility to senior engineer Louis Stevens in late 1953 -- ran what was essentially a bootleg project.
When management back East got wind of the project, it sent stern warnings that RAMAC be dropped because of budget difficulties. But the brass never quite caught up with the cowboys in San Jose.
[...]
In 1956, the Univac operation in St. Paul, Minn., was ready to bring a disk drive to market. But for political reasons, it didn't. Univac in Philadelphia wanted to stick with 18-inch drums. And Philadelphia had more clout. The city was the heart of computer activity because of the fact that it was there, at the University of Pennsylvania, that J. Presper Eckert and John Mauchly, senior people at Univac, had developed the pioneering ENIAC computer in 1946.
The decision to stick with drums rather than switching to disks has been described as not the only bad decision by Univac, but one that ranks right up there with the worst.

IBM's RAMAC could only be leased, not purchased. The lease price, per year, was about $10,000, or in inflation- adjusted dollars, about $85,000. The RAMAC enclosure cabinet dimensions were 60" × 60" × 29", giving a drive volume of 104,400 in³.

The RAMAC stored 5 megabytes across 50 disk platters, each 24" in diameter. Both surfaces of each disk were used (except for the top and bottom disks' outer surfaces), giving a surface area of ( 50 × 2 - 2 ) × π × (24 / 2) ² = 44,334 in². The disks rotated at the rate of 1,200 revolutions per minute, the average seek time to a track was over half a second, and the transfer rate was up to 8,800 bytes per second.

The RAMAC weighed one ton. Based on my estimates from the data available at the links below^[6], it consumed about 5 kilowatts. (This required air conditioning, which I have estimated from the available data as itself requiring about the same volume, weight, and power as the RAMAC, so I'm going to score that as an improvement of 2 × 2 × 2.)

The folowing table compares the original RAMAC parameters to the currently selling Maxtor DiamondMax II^®.

Parameter	RAMAC	Modern	Improvement
Capacity (bytes)	5,000,000	500,000,000,000	100,000
Price in $ / 5 years (Inflation adjusted)	425,000	250	1,700
Transfer Rate (bytes/s)	8,800	300,000,000	34,000
Average Seek Time (s)	0.6	0.0085	71
Volume (in³)	104,400	23	4,540
Power (watts)	5,000	10	500
Weight (oz)	32,000	25	1,280
Air Conditioning	6	N/A	6
Surface Area (in²)	44,334	58	764
Rotational Speed (RPM)	1,200	7,200	6

For the sake of illustration, the improvements noted in bold above can unreasonably be multiplied together to get an overall impression of the total improvement:

In its 50 years, computer disk memory has improved
by a factor of 7.154 × 10²⁴, or 7.154 septillion
or7,154,000,000,000,000,000,000,000.

References:

Following are annotated images of the IBM 305 & the IBM 350 RAMAC.

The stand-alone IBM 350 RAMAC disk drive.

A RAMAC drive behind the 305 operator's console, for scale.

Full image of IBM 305 with IBM 350 RAMAC drive.