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IBM 3375

From Alfawiki
Adapted from the English Wikipedia article IBM 3375, available under CC BY-SA 4.0Updated 9 August 2025
IBM Magnetic Disk Storage Division
Company typeDivision
IndustryComputer storage devices
Founded1956
Defunct2003
FateDivested to Hitachi
Key people
Currie Munce (Hitachi Global Storage Technologies, related)
ProductsHard disk drives, floppy disk drives
ParentIBM

IBM was a producer of magnetic disk storage devices from 1956 until 2003, at which point it divested its hard disk drive division to Hitachi. IBM's workforce was responsible for inventing both the hard disk drive (HDD) and the floppy disk drive (FDD), pioneering numerous advancements in these fields. The fundamental mechanical structure of hard disk drives has largely remained unchanged since the introduction of the IBM 1301, with performance and specifications still evaluated according to standards set in the 1950s. Over time, these devices have experienced dramatic reductions in cost and physical dimensions, alongside substantial improvements in capacity and speed.

Between 1969 and the mid-1980s, IBM manufactured 8-inch floppy disk drives but did not significantly participate in the markets for smaller 5.25- or 3.5-inch floppy drives. While IBM sold its magnetic disk drives directly, it only started supplying them under original equipment manufacturer (OEM) agreements beginning in 1981. By 1996, IBM had discontinued producing HDDs exclusive to its own systems, instead offering all drives as OEM products.

IBM employed several names for its magnetic disk storage units, such as direct-access storage device (DASD), disk file, and diskette file; however, this article adopts the widely recognized industry terms hard disk drive (HDD) and floppy disk drive (FDD).

IBM 350

The IBM 350 disk storage unit—recognized as the first commercial disk drive—was unveiled on September 14, 1956, as an integral component of the IBM 305 RAMAC computer system. A comparable model, the IBM 355, was introduced for use with the IBM 650 RAMAC system. The initial prototype was delivered to Zellerbach Paper Company in June 1956, with production units reaching customers such as United Airlines starting in November 1957.

Engineered to support real-time business accounting operations, the IBM 350 held 5 million six-bit characters (equivalent to 3.75 MB) across fifty-two disks each measuring 24 inches in diameter, utilizing one hundred recording surfaces. The disks rotated at a speed of 1200 revolutions per minute, enabling a data transfer rate of 8,800 characters per second. A mechanical access system moved read/write heads to select specific disk pairs and tracks. Several enhanced versions were launched throughout the late 1950s. The IBM RAMAC 305 system equipped with the IBM 350 was leased at $3,200 per month until its withdrawal in 1969.

A pivotal patent from this project—US3,503,060—is regarded as foundational for disk drive technology. Although initially halted by IBM’s Board due to concerns over potential negative effects on punch card sales, development persisted at IBM’s San Jose facility until receiving approval from IBM's president.

The unit measured roughly 60 inches in length, stood 68 inches tall, and was about 29 inches wide; it weighed approximately one ton and required forklifts for handling. According to Currie Munce of Hitachi Global Storage Technologies (the company that acquired IBM’s storage division), marketing considerations limited further capacity increases despite technical possibilities; nevertheless, double-capacity models were announced and shipped in January 1959.

In recognition of its significance, the RAMAC 350 Disk File was named an International Historic Landmark by The American Society of Mechanical Engineers in 1984. Restoration efforts commenced in 2002 under Al Hoagland’s leadership in cooperation with Santa Clara University and were later transferred to the Computer History Museum in Mountain View, California in 2005, where it remains on public display.

IBM 353

The IBM 353, utilized with the IBM 7030, bore resemblance to the IBM 1301 but offered a higher data transfer speed. It provided storage for 2,097,152 (221) words of 64 bits each (totaling 134,217,728 bits) and achieved a transfer rate of 125,000 words per second. A prototype delivered in late 1960 was notable as the first disk drive employing a dedicated head per surface that floated on compressed air, similar to the IBM 350 disk storage (RAMAC). Production versions adopted self-flying heads comparable to those found in the 1301.

IBM 355

Introduced on September 14, 1956, the IBM 355 was designed as an accessory to the widely used IBM 650 system. It incorporated the IBM 350 mechanism but featured up to three access arms—unlike the single arm on the IBM 350—enabling storage of six million decimal digits along with 600,000 sign indicators. The device transferred an entire track to and from the magnetic core memory of the 653, an optional IBM 650 component holding sixty signed ten-digit words, which matched the capacity of one disk track or tape record.

IBM 1405

The IBM 1405 Disk Storage Unit, launched in 1961 for use with the IBM 1400 series business computers, was available in two variants. Model 1 held ten million alphanumeric characters (equivalent to sixty million bits) distributed across twenty-five disks; Model 2 doubled this capacity to twenty million characters (one hundred twenty million bits) on fifty disks. The disks rotated vertically at a speed of 1200 rpm.

Each side of a disk contained two hundred tracks segmented into five sectors (numbered 0–4 on the top surface and 5–9 on the bottom), with each sector storing either 178 or 200 characters. One to three forked access arms—each equipped with two read/write heads for both top and bottom surfaces—moved vertically and horizontally under electronic control to access specific disks and tracks. Reading or writing a sector required approximately ten milliseconds.

Access durations ranged from one hundred milliseconds up to a maximum of seven hundred milliseconds for Model 1 and eight hundred milliseconds for Model 2. Model 2 comprised one hundred thousand sectors containing either two hundred characters in move mode or one hundred seventy-eight characters in load mode, which incorporated a word mark bit per character. Model 1 had half this number of sectors.

IBM 7300

The IBM 7300 Disk Storage Unit was engineered for compatibility with the IBM 7070. Although IBM announced a second model in 1959, users of the IBM 7070 and IBM 7074 preferred the IBM 1301 following its release on June 5, 1961. The technology underlying the IBM 7300 shared elements with the IBM 350, IBM 355, and IBM 1405 models.

IBM 1301

Unveiled on June 2, 1961, the IBM 1301 Disk Storage Unit was aimed at supporting the IBM 7000 series mainframe computers as well as the IBM 1410. Each module stored twenty-eight million characters (one hundred sixty-eight million bits), or twenty-five million characters when used with the IBM 1410. Modules contained twenty-five large disks providing forty user-accessible recording surfaces and two hundred fifty tracks per surface. The Model 1 configuration included a single module; Model 2 stacked two modules vertically. Disks rotated at eighteen hundred rpm and transferred data at ninety thousand characters per second.

A significant advancement was its design featuring an individual arm and disk head for each surface that moved simultaneously in unison like a comb. This innovation eliminated delays caused by repositioning heads over multiple disks and reduced maximum access time to one hundred eighty milliseconds. Additionally, it was the first disk drive to utilize aerodynamically shaped heads that floated on a thin cushion of air, enabling them to operate closer to the disk surface and thereby enhancing performance.

Connection was established through the IBM 7631 File Control unit, permitting operation with either an IBM 1410 or a member of the IBM 7000 series computers, or even allowing shared use between two systems.

Leasing charges for the IBM 1301 Model 1 were $2,100 per month or $115,500 for purchase; Model 2 leased at $3,500 monthly or $185,000 to buy. The IBM 7631 controller carried additional costs of $1,185 monthly or $56,000 if purchased outright. All models were discontinued by 1970.

IBM 1302

Launched in September 1963, the IBM 1302 Disk Storage Unit offered a fourfold increase in capacity compared to the IBM 1301, accommodating 117 million 6-bit characters per module. It delivered an average access time of 165 milliseconds and achieved data transfer speeds of 180,000 characters per second—more than twice as fast as its predecessor. Each module incorporated dual access mechanisms designed for the inner and outer cylinder groups. The Model 2 variant doubled storage by stacking two modules together. Leasing fees were set at $5,600 monthly for Model 1 and $7,900 for Model 2, with purchase prices of $252,000 and $355,500 respectively; the IBM 7631 controller was available separately at $1,185 per month or $56,000 for outright purchase. The IBM 1302 was discontinued in February 1965.

IBM 1311

Introduced on October 11, 1962, the IBM 1311 Disk Storage Drive catered to medium-sized business and scientific computing systems. Roughly the size of a top-loading washing machine, it stored two million characters on a removable IBM 1316 disk pack. Throughout the 1960s, seven different models were released before being phased out by the early 1970s.

Each IBM 1316 disk pack measures about four inches in height and weighs approximately ten pounds. It contains six disks with a diameter of 14 inches each, offering ten recording surfaces since the outer surfaces remain unused. The drive employs ten read/write heads mounted on a shared actuator that moves hydraulically over the tracks while disks spin at 1500 revolutions per minute. Every surface holds 100 tracks with 20 sectors per track; each sector stores 100 characters. The disk pack is enclosed in a transparent plastic casing equipped with a locking mechanism to facilitate straightforward installation and removal—an approach that later became standard across the industry.

The seven IBM 1311 models include both master drives equipped with controllers and slave drives without controllers. Master units can manage multiple slave drives—supporting up to four or three depending on system compatibility—with versions designed for systems such as IBM 1401, IBM 1440, IBM 1460, IBM 1410, IBM 7010, IBM 7740, IBM 1620, and IBM 1710.

Several optional capabilities improved functionality:

  • Direct Seek: Removes the need to return to track zero before seeking a new track.
  • Scan Disk: Provides fast automatic search capabilities.
  • Seek Overlap: Permits simultaneous seek operations and read/write tasks across multiple drives.
  • Track Record: Enhances storage by writing one large record per track instead of multiple sectors; this method can increase total capacity up to roughly 18.7 million bits under certain configurations.

Master models (1,3,4,5) feature additional power supplies and control circuitry and are approximately one foot wider than Model 2 slave units.

IBM 2302

The IBM 2302 serves as the System/360 counterpart to the IBM 1302, modified to align with S/360 DASD architecture. It utilizes a fixed module containing 25 platters with a total of 46 recording surfaces. The Model 3 includes one such module, while Model 4 incorporates two modules. Each module is equipped with two separate access mechanisms targeting the innermost and outermost sets of 250 cylinders—referred to as access groups—each having one read/write head per track. Average rotational latency is approximately 17 milliseconds with a maximum of 34 milliseconds; maximum seek time within each access group is up to 180 milliseconds. Tracks hold about 4,985 bytes each, resulting in a formatted module capacity of roughly 112 megabytes including alternate tracks. Connectivity to IBM mainframes is established through the IBM 2841 Storage Control Unit.

IBM 2305

Launched in 1970, the IBM 2305 fixed-head storage device, paired with the IBM 2835 Storage Control, initially interfaced with System/360 models 85 and 195 through the IBM 2880 Block Multiplexor Channel.

During the System/370 period, particularly with Virtual Storage, the 2305 was frequently employed as a paging storage unit on systems such as the 3155, 3165, 3158, 3168, 3033, 4341, and the 3081 (which required specialized microcode). It was also well-suited for handling high-transaction small data sets like catalogs and job queues.

The 2305-1 variant delivers a capacity of 5.4 MB with a data transfer rate of 3.0 MB/s and an average access latency of 2.5 ms. In contrast, the larger 2305-2 provides 11.2 MB storage at a transfer speed of 1.5 MB/s and an average access time of 5 ms.

Engineered for rapid and continuous access to modest-sized data volumes, the 2305 is ideal for system-resident tasks, work files, job queues, indexes, and frequently accessed data sets. Its swift response time makes it particularly effective as a paging device in systems managing workloads exceeding 1.5 transactions per second.

IBM 2311

Introduced in 1964 alongside the 2841 Control Unit, the IBM 2311 Disk Storage Drive was designed for use across the IBM System/360 family as well as the IBM 1130 and IBM 1800. It also supported direct connections to the IBM System/360 Model 20 and Model 25. All units utilized the removable IBM 1316 Disk Pack, originally introduced with the IBM 1311.

The Model 1 connects to most IBM mainframes via the 2841 Control Unit; however, on the Model 25 it interfaces through a Disk Attachment Control that acts as its control unit. The disk packs employ IBM's count key data format with variable record lengths.

Models designated as 11 or 12, intended for the System/360 Model 20's integrated control architecture, use fixed-sector disk packs that are incompatible with those used by Model 1 drives.

Mechanically akin to the IBM 1311 but with enhanced recording density, the 2311 stores up to 7.25 megabytes on a removable disk pack comprising six platters. It features ten read/write heads mounted on a hydraulically actuated arm; each disk surface contains 200 tracks plus three optional spare tracks for defects. The average seek time is approximately 85 ms, with a data transfer rate of about 156 kB/s.

Uniform electrical interfaces across System/360 models allowed third-party vendors to develop plug compatible disk drives, promoting a competitive aftermarket around IBM’s ecosystem.

IBM 2314 Disk Access Storage Facility Model 1

Released in April 1965 for System/360 and System/370 systems, the IBM 2314 featured a Two Channel Switch enabling connection to two channels concurrently. While its disk mechanism resembled that of the IBM 2311, it supported significantly higher data density.

The associated IBM 2316 disk pack contained eleven disks of diameter , offering twenty recording surfaces each with approximately 200 tracks. This arrangement provided storage capacity near twenty-nine million characters (calculated as twenty surfaces × approximately seven thousand two hundred ninety-four bytes per track). Twenty read/write heads were mounted on a hydraulically actuated arm for data access; subsequent models improved access times by upgrading actuator technology. Data transfer rates doubled to around 310 kB/s compared to earlier devices.

The original Model 1 was sold as an assembly of nine drives housed together; separately shipped components included a storage control unit plus one single-drive module and two four-drive modules. Drives were installed in drawers facilitating easy disk pack handling—earning them the nickname "Pizza Ovens." Only eight drives operated simultaneously while the ninth served as an offline spare to allow maintenance without interrupting system operations. Drive addresses were configured via user-swappable plugs permitting flexible reassignment and designation of spares.

An optional IBM 2844 Control Unit allowed two System/360 channels to access different drives within the facility at the same time.

Subsequent versions of the IBM 2314 were introduced later:

IBM 2314 Direct Access Storage Facility - Model Variants

In 1969, IBM diversified the 2314 storage system into several models designed to support up to nine disk drives, with eight accessible online, all managed through a 2314 Storage Control. These included:

  • The 2312 Disk Storage, featuring a single drive module.
  • The 2313 Disk Storage, comprising four drives.
  • The 2318 Disk Storage, containing two drives.

IBM 2319

To counter competition from plug compatible manufacturers offering alternatives to the 2314 storage, IBM launched the cost-effective three-drive 2319 series in 1970. This was achieved by reducing one drive from the four-drive 2313 and renaming it as the 2319 A1, which was marketed at a notably lower rental fee. This approach enabled IBM to offer more affordable options to new customers while retaining higher pricing for existing clients. The 2319-A1 interfaces with integrated controllers designed for System/370 Models 135 and 145. Additionally, traditional 2314 DASD units such as the 2312 or 2318 can connect to the 2319-A1. The 2319 B series expanded support for configurations of three, six, or nine drives connected to an updated 2314 Model B Storage Control Unit.

IBM 3310

Released on January 30, 1979, the IBM 3310 Direct Access Storage Device was developed specifically for IBM 4331 midrange computer systems. Each unit provided a storage capacity of 64.5 MB. Utilizing fixed-block architecture, the 3310 was compatible with DOS/VSE and VM operating systems that supported FBA devices.

IBM 3330

The IBM 3330 Direct Access Storage Facility, internally known as Merlin, debuted in June 1970 targeting IBM System/370 and System/360/195 platforms. Initial offerings included a two-drive Model 1 and a single-drive Model 2. Removable disk packs held up to 100 MB (404×19×13,030 bytes), featuring an access time of approximately 30 ms and a data transfer rate of 806 kB/s. A significant advancement was the incorporation of error correction via fire codes, which boosted reliability and lowered expenses by allowing tolerance for disk surface defects.

The original configuration consisted of one storage control unit (3830 Model 1) connected to a chain of up to four drives (with a maximum of eight drives per string). In August 1972, IBM introduced the 3830 Model 2 Storage Control along with the 3333 Disk Storage and Control, which separated control functions from drive strings. The 3830 Model 2 served as a director-type controller overseeing multiple strings; meanwhile, each string's first unit—the 3333—combined a controller with two drives and could manage up to three additional attached 3330 units (allowing up to eight drives per string). Up to two 3333 units could connect to one controller, supporting as many as sixteen drives per storage control system. An optional string switch on the 3333 enabled connection to two separate controllers.

In 1973, IBM launched double-density (-11) variants including the 3333–11, 3330-11, and 3336–11 models, which doubled disk pack capacity to 200 MB (808×19×13,030 bytes). It was not possible to mix single-density and double-density drives within the same string. Although field upgrades from base models to Model-11 versions were available, these required drive modifications and complete data migration.

The IBM 3330 product line was phased out in 1983.

IBM 3340 and IBM 3344

While both the IBM 3340 and 3344 share many characteristics, only the IBM 3340 can act as the head of a drive string. Notably, there are no A model versions of the IBM 3344; thus, a 3344 unit must be connected under a head-of-string IBM 3340 A model controller.

IBM 3340

Introduced in March 1973 for the IBM System/370, the IBM 3340 Direct Access Storage Facility, known by its code name Winchester, came in three variants: the 3340-A2 (which included two drives plus a controller), and the B2 (two drives) and B1 (single drive) models. B-units could be connected to an A2 controller, supporting up to eight drives in total.

This system employed removable data modules that housed both the head and arm assemblies. Unlike earlier disk packs, these modules did not require cover removal; instead, a mechanical access door would open or close to load or unload the module. The device achieved an average access time of 25 milliseconds and supported data transfer rates of 885 kB/s. Three versions of the IBM 3348 Data Module were marketed: one with a 35 MB capacity and two with 70 MB, one of which included a fixed-head area of 500 KB for faster access. The IBM 3340 also incorporated error correction capabilities and was discontinued in 1984.

Development took place in San Jose under Ken Haughton's leadership, initially targeting two removable modules with 30 MB each. The "Winchester" nickname originated from this original 30/30 design, referencing the Winchester .30-30 rifle. Although storage capacities increased over time, the nickname persisted.

A major breakthrough was the introduction of a cost-effective head design that allowed the read/write heads to land on and lift from the disk surface while it was spinning up or down without unloading completely. This "Winchester technology" greatly simplified the head and arm mechanism, reducing manufacturing costs and complexity, ultimately setting a new industry benchmark.

Throughout the early 1990s, terms like "Winchester" or "Winnie" were widely used as synonyms for hard disk drives but have since become obsolete worldwide.

IBM 3344

The IBM 3344 shared similarities with the 3340 but differed by utilizing fixed media instead of removable IBM 3348 data modules. Each spindle supported four logical drives, each matching the capacity of a 70 MB 3348 module. This model was exclusively available as dual-drive units and did not include an A (head-of-string) variant. The 3344-B2F differed from the B2 model by having fixed heads over certain cylinders on both drives. Both required connection to a 3340-A2 or 3340-A2F unit acting as the head-of-string controller. Internally, the IBM 3344 was essentially identical to the IBM 3350 except for differences in control unit microcode.

IBM 3350

Released in 1975 for IBM System/370, the IBM 3350 Direct Access Storage Facility bore the code name Madrid. It introduced sealed, non-removable head-disk assemblies (HDAs) that integrated both heads and arm assemblies within a sealed enclosure. The disk configuration comprised 555 cylinders and 30 heads, with each track containing 19,069 bytes, resulting in an approximate capacity of 317 MB per HDA. This sealed HDA design became standard practice for all subsequent IBM DASD products.

Models A2, A2F, B2, B2F, C2, and C2F were all equipped with two HDAs each. The A2 and A2F models included an additional electronics board that enabled connection to control units; these served as controllers or head-of-string devices. Storage strings began with an A2 or A2F unit followed by up to three B2 units or various combinations of B2s and C2s. Typically, the A2 unit contained a string switch allowing dual connections to storage control units so that simultaneous I/O operations could occur on two separate HDAs.

Compatible storage control units encompassed models such as the 3830 Model 2 and Integrated Storage Control (ISC) within CPUs like the 3148, 3158, or 3168; later controllers including the IBM 3880 maintained backward compatibility. The C2 model also housed a controller acting as a secondary path but was only activated if the A unit’s controller failed and was powered down. Accepted IBM 3350 string configurations included combinations such as -A, -AB, -ABB, -ABBB, -AC-, -ABC-, and -ABBC-.

The "x2F" variants (for example, A2F) featured fixed-head regions covering the first five cylinders on both HDAs to eliminate seek delays within this area. This section was commonly reserved for frequently accessed checkpoint data in HASP or JES2 spooling systems to improve performance by reducing head movement times. Additionally, it served as swap space in TSO environments and system swap areas under operating systems like MVT, SVS, and MVS—thereby enhancing context switching efficiency between users or batch tasks.

The IBM 3350 series was officially withdrawn from commercial availability in September 1994.

IBM 3370

In January 1979, IBM introduced the IBM 3370 Direct Access Storage Device designed for use with IBM 4331, 4341, and System/38 midrange systems. This device incorporated seven fixed 14-inch platters, delivering a storage capacity of 571 MB per unit. Notably, the 3370 was the pioneer in employing thin-film head technology, which was developed at the Thomas J. Watson Research Center during the late 1960s. It functioned using a fixed-block architecture and was compatible with DOS/VSE and VM operating systems running on S/370 hardware.

IBM 3375

The IBM 3375 served as a complementary product to the 3370, utilizing count key data (CKD) architecture. It was designed to support OS/360 and its subsequent operating system versions.

IBM 3380

Launched on June 11, 1980, the IBM 3380 Direct Access Storage Device employed thin-film head technology and provided a total capacity of 2.52 GB per unit, consisting of two hard disk assemblies each featuring dual actuators accessing 630 MB. The device achieved a data transfer speed of 3 MB/s with an average access latency of 16 milliseconds. Initial pricing ranged between $81,000 and $142,200. Due to tribological challenges affecting the interaction between heads and media surfaces, shipments commenced only in October 1981.

The typical setup comprised one A unit plus up to three B units; each 3380 contained four devices, enabling configurations with up to sixteen devices per string. Usually connected via dual paths to a 3880 storage control unit, it supported two concurrent I/O operations directed at different hard disk assemblies.

In February 1985, IBM released the Extended Capability Models (3380 E) featuring double density with a capacity of 5.04 GB per unit—achieved through two actuators each managing 1.26 GB over two assemblies. The triple-capacity Model K arrived in August 1987, offering 7.562 GB per unit through two actuators at 1.89 GB each. Both Models J and K were capable of four-path operation when linked to a 3990 storage control unit, allowing up to four simultaneous I/O processes across strings containing as many as thirty-two devices.

The IBM 3380 series consisted of twelve models: six A-units acting as string leaders with controller logic interfacing with IBM storage control units; five B-units connecting to either A- or C-units; and one C-unit designed for direct connection to an IBM channel.

After an impressive production span exceeding fifteen years—surpassing typical disk drive lifetimes—manufacturing concluded in May 1996.

IBM 3390

Debuting in November 1989, the IBM 3390 Direct Access Storage Device series provided storage capacities reaching up to 22 gigabytes distributed across multiple drives. System pricing varied from $90,000 to $795,000 depending on configuration and total capacity.

A standard 3390 string comprised a central A unit containing four or eight devices, optionally supplemented by one or two B units holding up to twelve devices each. Operating in four-path mode, it connected to a 3990 storage control unit capable of supporting an additional 3390 string, allowing a maximum of sixty-four devices within a subsystem.

Hard Disk Assemblies (HDAs) incorporated two actuator-head units along with platters: Model 1 offered an unformatted capacity of 1.89 GB; Model 2 doubled this to 3.78 GB per HDA. The Model 3 upgrade introduced in 1991 increased capacity by fifty percent to reach 5.67 GB per HDA, while Model 9 in 1993 tripled capacity further to achieve 11.3 GB per HDA.

Unlike earlier DASD designs that utilized belt-driven AC motors, the HDAs in the IBM 3390 employed direct-drive DC motors enclosed within the device.

The Model 9 represented IBM’s final iteration of the Single Large Expensive Disk (SLED) drive architecture.

IBM 9345

Released in November 1990 as a Request Price Quotation (RPQ) under IBM’s SuperComputing Systems Extensions (SCSE), the IBM 9345 hard disk drive was engineered at IBM’s San Jose facility, codenamed Sawmill. This full-height 5¼-inch HDD featured eight 130 mm platters and offered a maximum storage of 1.5 GB. It holds the distinction of being the first hard drive to incorporate Magnetoresistive (MR) read/write heads.

IBM 9340

The IBM 9345 was complemented by the introduction of the IBM 9340 in October 1991. This direct access storage device (DASD) was part of the 9340 series, a channel-attached CKD DASD subsystem designed for IBM mainframes, including the ES/9000 line. The Model 1 configuration contained two HDDs each with 1.0 GB capacity, while Model 2 comprised two HDDs with 1.5 GB each.

In terms of performance, the 9340/9345 series paralleled the functionality of the IBM 3990/3390 drives but did not include the non-volatile RAM cache found in the 3990. Additionally, its maximum block size was smaller than that of the 3390. Within the operating system, identification was managed by the IOS component through a specialized initializer named IECCINIT, which detected the absence of non-volatile cache on the 9340 and adjusted for the reduced track count on the 9345, assigning a unique device type accordingly.

9330 family of disk drives

  1. The 9331 Diskette Unit models 1 and 11 were equipped with a single 8-inch floppy disk drive; models 2 and 12 featured one 5-inch floppy disk drive.
  2. The 9332 Direct Access Storage Device utilized IBM’s 0667 hard disk drive.
  3. The 9333 High Performance Disk Drive Subsystem employed either IBM 0664 or IBM 0681 HDDs depending on model specifications.
  4. The 9334 Disk Expansion Unit allowed connection of one to four SCSI hard drives to RS/6000 systems.
  5. The 9335 Direct Access Storage Subsystem incorporated the “Kestrel” HDD developed at IBM Hursley, UK—an 850 MB device comprising three 14-inch platters and dual rotary actuators enabling access to multiple surfaces. This rack-mounted unit was launched alongside the October 1986 announcement of the IBM 9370 Information System. No known OEM variants exist.
  6. The 9336 Disk Unit utilized the IBM 0681 HDD, also known as Redwing.
  7. The 9337 Disk Array Subsystem employed IBM’s 0662 (Spitfire) or 0663 (Corsair) hard disk drives.

IBM 2310

Introduced in 1964 with the IBM 1800 and subsequently in late 1965 with the IBM 1130, the IBM 2310 Removable Cartridge Drive stored data on an IBM 2315 cartridge containing a single, oxide-coated aluminum platter measuring fourteen inches in diameter within a plastic casing that provided openings for read/write arm access and two heads. It held up to 512,000 sixteen-bit words, equivalent to approximately one megabyte (1,024,000 bytes).

IBM 5444

The IBM 5444, launched in September 1969 as part of System/3 and developed at IBM's Hursley laboratory under the codename Dolphin, used a disk cartridge designated as model 5440 containing one fourteen-inch platter. It was available in three configurations:

  • Model 1: one fixed disk plus one removable disk, each with one hundred tracks per surface; cartridge capacity of approximately 1.23 MB
  • Model 2: one fixed disk plus one removable disk, each featuring two hundred tracks per surface; cartridge capacity around 2.46 MB
  • Model 3: a single removable disk with two hundred tracks per surface; cartridge capacity approximately 2.46 MB

IBM 62GV

First shipped in May of 1974 from IBM’s Hursley facility under project name Gulliver, the IBM 62GV initially offered five megabytes of storage capacity. Subsequent versions expanded this to ten megabytes (62TM) and ultimately fourteen megabytes. It incorporated a Swinging Arm actuator paired with a single fourteen-inch platter—a design innovation from Hursley that became IBM’s most widely licensed electro-mechanical invention. This actuator mechanism along with its filtration system gained broad adoption throughout the HDD industry during the 1980s and remained an industry standard for nearly four decades, with over ten billion arms produced worldwide. The model achieved sales exceeding approximately one hundred seventy-seven thousand units, marking it as the first hard drive to surpass one hundred thousand units sold.

OEM and Small Systems Hard Drives

This segment details IBM hard disk drives provided as OEM components and for IBM's smaller systems, including the System/3, System/32, /34, /36, and AS/400. Each drive is identified by its OEM model number and organized according to its initial shipment date.

IBM 0680

The 0680 was initially delivered in 1979, serving most IBM small systems and entry-level System/370 models as the 3310 direct access storage device. Officially announced as the 0680 in September 1981, it was created at IBM's Hursley laboratory in the UK under the project name Piccolo. This drive comprised six 8-inch (210 mm) platters, providing a starting capacity of up to 65MB and featuring an enhanced rotary actuator.

A higher-capacity variant, the 62SW, became available in June 1984; however, its adoption was limited due to a cost per megabyte comparable to that of the 62GV.

IBM 0676

Introduced in November 1982, the 0676 functioned as a 5247 Disk Storage Unit designed for the IBM System/23 Datamaster. Developed at IBM Rochester, Minnesota under the designation 21ED, this 8-inch hard drive initially offered capacities of either 15 or 30 MB through configurations of two or four platters. In 1983, it was integrated into the System/36’s 5360 System Unit. By 1984, capacity was doubled by increasing track density per surface, and it was subsequently incorporated into the System/36’s 5362 System Unit.

IBM 0665

Launched in October 1985 within the PC AT (5170) system unit, the 0665 was developed at IBM Rochester under the codename "Pixie." This 5¼-inch hard disk drive came with capacity options of 20, 30, and 44 MB.

IBM 0667

Released beginning in August 1986, the 0667 was a full-height ESDI hard drive measuring 5¼ inches. Created at IBM Rochester under the codename "Grant," it supported up to four 130 mm platters with a maximum capacity of 70 MB. It was installed in select PC RT models (6150, 6151, and 6152) as well as System/36 Model System Units (5363 and 5364).

IBM 0669

The 0669, introduced in 1987 and developed at IBM Rochester, Minnesota under the codename "Grant-Prime," was a full-height 5-inch hard disk drive. It featured up to four 130 mm platters delivering a capacity of up to 115 MB. This drive served as the internal storage solution for both the System/36 Model 5363 and Series 1 Model 4956 System Units.

IBM 0671

Also launched in 1987 and developed at IBM Rochester with the codename "Lee," the 0671 was an ESDI full-height hard drive measuring five inches. Equipped with up to eight 130 mm platters, it provided capacities reaching up to 316 MB and represented IBM’s initial use of a thin metal film recording surface. In 1988, it was incorporated into the AS/400 system’s Model 9404 System Unit, supporting configurations of two or optionally three drives.

IBM 0661

The 0661 appeared in 1989 as model number 371. Developed under the codename "Lightning" at both IBM Rochester and Hursley in the UK, this SCSI hard disk offered a capacity of 320 MB using eight platters sized at 95 mm with fourteen heads. A subsequent "Turbo" version increased capacity to 400 MB in 1990. It became a standard component on key IBM platforms such as the AS/400 System Unit Model CXX.

IBM 0681

Introduced in April 1990 from IBM Hursley and known internally as Redwing, the 0681 was the final hard drive developed at that facility. This full-height five-inch HDD utilized twelve platters of 130 mm diameter to achieve capacities up to 857 MB and was notable for being IBM’s first drive employing PRML data decoding technology. It powered the launch of the 9333 Disk Drive Subsystem in early 1992, with an upgraded high-density variant offering up to 1.07 GB released in May of that year.

IBM 0663

Introduced in late 1991 and internally known as "Corsair," the 0663 was a compact 3-inch hard disk drive with a half-height (1.6-inch) profile, delivering up to 1 GB across eight 95 mm platters. It appeared in select PS/2 and RS/6000 systems and marked IBM's inaugural use of Magnetoresistance (MR) heads in an OEM disk drive.

IBM 0664

Released in November 1992, the 0664 was developed at IBM Rochester, Minnesota, under the codename "Allicat." This full-height 5-inch HDD (3.25 inches tall) essentially combined two 3-inch drives, providing a maximum capacity of 2.013 GB using up to eight 95 mm platters.

IBM 0662

The 0662, launched in June 1993 and codenamed "Spitfire" at IBM Rochester, was a full-height (1 inch tall) 3-inch hard drive offering 1.05 GB storage via three platters or five recording surfaces. It functioned as the internal hard disk for the 9336 Disk Unit and the 9337 Disk Array.

Floppy disk drive

IBM was a pioneer in floppy disk technology, debuting the 8-inch floppy disk drive in 1971 initially as a read-only program loader and introducing its first read/write version in 1973 with the 3740 Data Entry System. Although IBM established early standards for 8-inch floppy drives, it did not market them separately, enabling industry-wide development to proceed independently.

At one point, IBM was the largest buyer of OEM 5-inch floppy drives worldwide. Its selection of two-sided drives with a track density of 48 tracks per inch helped set this configuration as an industry benchmark. Despite preparations to produce smaller form factors, IBM abandoned these plans by 1985. The company’s 1983 attempt to OEM the 4-inch DemiDiskette did not succeed.

"Star" series of HDDs

On October 17, 1994, IBM's Storage Systems division introduced three families of hard drives: the Travelstar series featuring 2-inch drives designed for notebooks, the Deskstar line with 3-inch drives aimed at desktop computers, and the Ultrastar series of 3-inch drives engineered for high-performance systems.

IBM's first HDD versus its last HDDs

The table below contrasts IBM’s original hard drive, the RAMAC 350, with its final three models from the "Star" series of OEM HDDs. The comparison highlights substantial reductions in physical size and cost alongside remarkable improvements in storage capacity and performance over a span of 46 years.

Parameter (units) RAMAC 350 Ultrastar 146Z10 Deskstar 180GXP Travelstar 80GN Maximum improvement over 46 years
Announced Sep 1956 Jul 2002 Oct 2002 Nov 2002
Capacity (gigabytes) 0.004 146 180 80 48,000
Dimensions (inches) 60×68×29 4×1×5.75 4×1×5.75 2.75×0.38×3.95
Dimensions (mm) 1500×1700×700 102×25×146 102×25×146 70×9.5×100
Volume (in³) 118,320 23 23 4 29,161
Volume (litres) 1,939 0.4 0.4 0.1
Weight (lbs) 2,140 1.7 1.4 0.2 1,244
Weight (kg) 971 0.8 0.64 0.095
Power consumption (watts) Approx. 2374 watts (8100 BTUs/hour), up to 5500 VA depending on model 16 10.3 1.85 1,283
Power efficiency (megabytes/watt) 0.0016 9,125 17,476 43,243 27,375,856
List price (Template:US$) $34,500 ($234,000 adjusted to 2002 dollars) $1,200 $360 $420
Price per megabyte (Template:US$) $9,200 ($68,000 adjusted to 2002 dollars) 0.0082 0.0020 0.0053
Areal density (megabits/in²) 0.002 26,263 46,300 70,000
Areal density (kilobits/mm²) 0.003 40,708 71,765 108,500
Volumetric density (gigabytes/in³) 0.00000003 6 8 20
Volumetric density (megabytes/cm³) 0.000002 388 478 1,203
Rotational latency (ms) 25 3 4 7
Average seek time (ms) 600 5.9 10.2 12
Data transfer rate (megabytes/s) 0.001 103 29.4 43.75


DASD Devices Beyond HDDs and FDDs

Within certain IBM operating systems, hard disk drives (HDDs) and floppy disk drives (FDDs) are both categorized as DASDs (direct access storage devices). Additional technologies classified under DASD include:

IBM 7320 Drum

The IBM 7320 represents a magnetic drum storage unit that IBM launched in 1962.

IBM 2301 Drum

Introduced in the late 1960s, the IBM 2301 is another magnetic drum storage device developed by IBM.

IBM 2303 Drum

The IBM 2303, released in 1964, is a magnetic drum storage apparatus.

IBM 2321 Data Cell

Announced in 1964, the IBM 2321 Data Cell utilizes short strips of magnetic tape for data retention. It accommodates ten removable cells, each with a capacity of 40 MB, resulting in a total storage capability of 400 MB.

IBM 3850 Mass Storage System

The IBM 3850 Mass Storage System, introduced in 1974, functions as a tape cartridge library. It stages data onto IBM 3330 or 3350 disk drives and presents these as virtual drives to the host system.

See also

External links

Related profiles

IIBM 1311IIBM 0661IIBM 353IIBM 355
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