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1970Diablo 30 Series Cartridge Disk Drives

First Highly Successful OEM Cartridge Disk Drive Manufacturer


Why its important

The Diablo 31 became the dominant cartridge disk drive for minicomputers and early workstations. The small rack mount form factor and front load gave small computer users great flexibility in loading software, good mass storage performance, and essentially unlimited shelf storage capacity. This type of drive fostered the rapid growth of several minicomputer manufacturers and the development of more complex applications.


Diablo Systems Inc. Hayward CA, was founded July 1969 by George Comstock and Dr. Andrew Gabor. It wasinitially financed by Itel, and sold to Xerox in April 1972 for about $28M [Oakland Tribune, April 25, 1972] The company's first product was a front loading cartridge disk drive that used cartridges compatible to the IBM-2315. Initially offered as the Model 30 at 1.25 megabyte capacity, it was quickly replaced by the Model 31 with twice the capacity, 2.5 megabytes.

Dr. Gabor designed the drive with two technologies that were new to small disk drives - a rotary to linear positioner that used an Inductosyn for position feedback and a brushless DC motor as the power source. Another brushless DC motor was used as the direct drive spindle. The drive was rack mounted and power supplies were provided by the customer.

Digital Equipment Corporation was the first OEM customer and obtained a license to manufacture the product, but decided to design their own interface and cartridge compatible drive. Other notable customers were Data General and the Xerox PARC ALTO workstation.

Although not the first cartridge disk drive, (see IBM 2310), and probably the 3rd manufacturer of 2315 compatible cartridges to ship (it followed CMD and Iomec), Diablo became the dominant OEM supplier of cartridge disk drives in the 1970s.

FCS was to 1970 to Digital Equipment. DEC selected Diablo as a supplier before the first prototype was functional. <Note product shipped to DRI, Staines UK before August 1970 [Oakland Tribune, Aug 5, 1970] - I think this was the Europe licensee - Grant >

Probably the disk drive used on the "World's First Fully Functional Microcomputer (with peripherals)"

Diablo later offered a fixed plus removeable version of the Model 31. Diablo then expanded into the "daisy wheel" printer market, offering near IBM Selectric typewriter print quality for word processors.

Product Brochure attached

Additional Information
Oral History of George Comstock, CHM Accession #102658008

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Anonymous Diablo Model 30 Disk Drive 1 Dec 13 2012, 1:21 AM EST by Anonymous
Thread started: Nov 15 2012, 8:09 AM EST  Watch
Introduced in 1970 I was working for Diable and still selling Model 30 drives as late as 1980! The Model 30 was eclipsed by the Model 44A & B 5MB fixed 5MB 5440 removable.

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bcstractor IBM also had a top load cartridge 0 Feb 1 2009, 7:09 PM EST by bcstractor
Thread started: Feb 1 2009, 7:09 PM EST  Watch
I think it was called a 5440 and was in production in 1970/1. It was designed in Hursley and had a fixed disk that stayed with the machine. It was sold in two capacities. The lower capacity was achieved by blocking the travel of the leadscrew driven actuator. I remember the lubricant on the leadscrew - Moly Disulfide - it permanently stained my tie. Dolphin?
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Adobe Portable Document Format Diablo 30 PB 197201xx.pdf (Adobe Portable Document Format - 476k)
posted by tom94022   Dec 14 2008, 2:49 PM EST
Diable Series 30 Product Brochure Jan 1972