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1950s - 1970s

The IBM 350 Disk File, invented by Reynold Johnson, was introduced in 1956 with the IBM 305 RAMAC computer. This drive had fifty 24 inch platters, with a total capacity of five million characters A single head assembly having two heads was used for access to all the platters, making the average access time very slow (just under 1 second).
The IBM 1301 Disk Storage Unit announced in 1961, introduced the usage of a head for each data surface with the heads having self acting air bearings (flying heads).
Also in 1961, Bryant Computer Products introduced its 4000 series disk drives. These massive units stood 52 inches (1.3 m) tall, 70 inches (1.8 m) wide, and had up to 26 platters, each 39 inches (0.99 m) in diameter, rotating at up to 1200 rpm. Access times were from 50 to 205 ms. The drive's total capacity, depending on the number of platters installed, was up to 205,377,600 bytes, or 196 MiB.
The first disk drive to use removable media was the IBM 1311 drive, which used the IBM 1316 disk pack to store two million characters.
In 1973, IBM introduced the IBM 3340 "Winchester" disk drive, the first significant commercial use of low mass and low load heads with lubricated media. All modern disk drives now use this technology and/or derivatives thereof. Project head Kenneth Haughton named it after the Winchester 30-30 rifle because it was planned to have two 30 MB spindles; however, the actual product shipped with two spindles for data modules of either 35 MB or 70 MB.
Also in 1973, Control Data Corporation introduced the first of its series of SMD disk drives using conventional disk pack technology. The SMD family became the predominant disk drive in the minicomputer market into the 1980s.


IBM 3390 direct access storage device

  • Models A14, A18, B14, B18, B1C, A24, A28, B24, B28 and B2C announced November 14, 1989

  • Model 3 announced September 11, 1991

  • Model 9 announced May 20, 1993
When the IBM 3390 Direct Access Storage Device (DASD) was rolled out in November 1989, it offered up to 22.7 billion bytes (gigabytes) of storage and allowed customers to store more data in a single DASD than ever before.
Boosts in key DASD performance areas -- such as a 40 percent improvement in data transfer rate and 15 percent in average latency -- provided users with a highly reliable, cost effective means of rapidly accessing vast amounts of data.
The 3390 represented three times the storage capacity per square foot of floor space over the IBM 3380K; five times over the 3380 Model E; and ten times over 3380 standard models. The new DASDs also delivered an 18 percent reduction in the cost of a megabyte of disk storage.
Improvements in three key factors of DASD performance yielded an overall 20 percent improvement in subsystem response time. Seek times -- the time needed to position the read/write head over a track of data -- were reduced to an average of 12.5 milliseconds from 16.0 milliseconds for the IBM 3380K.
The 3390 disks rotated faster than those in the 3380. Faster disk rotation reduced rotational delay, the time required for the correct area of the disk surface to move to the point where data could be read or written. In the 3390's initial models, the average rotational delay was reduced to 7.1 milliseconds from 8.3 milliseconds for the 3380 family.
The data transfer rate -- the speed that data can move to and from the disk surface -- was also increased, from 3.0 megabytes per second for the 3380 family to 4.2 megabytes per second for the 3390.
The 3390 was designed to maximize reliability and data availability. It had fewer parts, cables and connections. Separate power and service boundaries for individual parts, such as controller cards and head disk assembly units (HDAs), isolated functional areas for servicing. (HDAs are self-contained units that hold the access arms, read/write heads, disks and motors.)
The 3390 Model 1 provided a storage capacity of 3.78 gigabytes to 11.35 gigabytes. The Model 2 had a capacity of 7.56 gigabytes to 22.7 gigabytes.
The 3390 attached via the IBM 3990 Storage Control Models 2 and 3 to all ES/3090 models and IBM 308x models through an additional attachment feature.
First customer deliveries of the 3390 Models 1 and 2 were scheduled for December 1989 at prices ranging from $90,000 to $275,000. A typical configuration consisting of three 3390 Model units was priced at $759,000.
Highlights of Model Groups 1 & 2 (c. 1989)
  • Four path data transfer
  • Designed for 3090 4.5MB/sec channels
  • Attached to 3090 and 308x (except 3081D) via 3990 Model 2 or 3
  • Coexisted with 3380D, E, J and K on 3990 Model 2 or 3
  • Compared to 3380: average seek time 28% faster, latency 17% reduction, transfer rate 40% faster.
3390 Models/Capacities (GB) (c. 1989)
2 model groups, 10 models
Track capacity increased by 19%.
# HDAs
Mes upgrades
A18, A24
B18, B24
B1C, B28

3390/3380 Performance Characteristics

MG 1
MG 2
Data rate MB/sec
Latency ms
Min. seek ms
Avg. seek ms
Max. seek ms


IBM 3380

The IBM 3380 Direct Access Storage Device was introduced in June 1980. It used new film head technology and had a capacity of 2.52 gigabytes with a data transfer rate of 3 megabytes per second. Average access time was 16 ms. Purchase price at time of introduction ranged from $81,000 to $142,200. Due to problems encountered, the first units did not ship until October, 1981.


IBM 3370 direct access storage device

IBM 3370 Direct Access Storage Device
  • Models A1, B1, A11, and B11 announced January 30, 1979 and withdrawn August 5, 1986
  • Models A2, B2, A12 and B12 announced September 15, 1983
The IBM 3370 of 1979 introduced thin-film head technology to large disk files. Work on thin-film head structures was started in IBM's Thomas J. Watson Research Center in Yorktown Heights, N.Y., in the late-1960s.
The 3370 direct access storage device (DASD) was an advanced fixed-media disk unit that initially provided 571.3 megabytes of auxiliary storage for IBM's 4331 and 4341 processors and the IBM System/38 midrange computer. Up to four 3370 devices could be attached to any System/38 Model 5 for an additional 2,285.5 megabytes of auxiliary storage.
Average seek time was 20 milliseconds and the nominal data rate was 1.859 megabytes per second.
Two 3370s were available in February 1980 for attachment to System/38: Model A11 attached to the IBM 5381 System Unit Model 5, and up to three Model B11s could be connected through an A11 unit.
At announcement, a Model A11 could be leased for $900 a month, rented for $1,058 a month or purchased for $35,100. Corresponding charges for each B11 unit were $600, $705 and $23,400.


IBM 3350 direct access storage

  • Models A2, A2F, B2 & B2F announced July 15, 1975 and withdrawn September 5, 1994

  • Models C2 and C2F announced November 4, 1975 and withdrawn September 5, 1994
Known during its development as "Madrid," the IBM 3350 was introduced in 1975 and first delivered the following year. It extended Winchester technology by increasing the number of disks per drive and the recording density to provide a 4.5 times increase in capacity per spindle. In addition, the developers eliminated the customer-removable disk pack and circled back to fixed disks, as in the IBM RAMAC, to achieve higher recording densities and lower cost per bit of online storage. In addition, the elimination of operator handling -- and exposure to external contamination -- provided high reliability.
The 3350 furnished a maximum storage capacity of approximately 317.5MB per drive (635MB per unit), allowing more than 2.5 billion bytes of online storage per 3350 string. The data rate was 1198K/second and average seek time was 25 milliseconds.
The 3350 Models A2F and B2F provided 1,144,140 bytes of zero seek time storage per spindle (2,288,280 per unit) when operating in 3350 native mode. Models A2 and A2F were two-drive units with associated controls, which attached to the IBM System/370 Models 135, 155-II and 165-II via the 3830 Model 2, and to the IBM System/370 Model 145, 158 and 168 via their ISCs and/or the 3830 Model 2. The 3350 Models B2 and B2F were two-drive units which attached to the 3350 Model A2 or A2F. Up to three B2 or B2F units could be attached to each A2 or A2F unit, for a maximum of eight drives per 3350 string.
Average seek time (ms): 25
Average rotational delay (ms): 8.4
Data Rate (KB/sec.): 1198
Bytes per track: 19,069
Tracks per logical cylinder: 30
Logical cylinders per drive: 555
Capacity per drive (MB) approx. 317.5
  • Rotational position sensing, which permitted improved block multiplexer channel utilization.

  • Error correction of single data error bursts of up to four bits.

  • Command retry, which enabled the storage control to recover from certain subsystem errors without recourse to system error recovery procedures.

  • Read only switch, gave increased data security by providing for each drive the means to protect data from being overwritten or erased.


IBM 3340

  • Models A2, B1 and B2 announced March 13, 1973

  • Models B1 and C2 withdrawn December 20, 1983

  • Models A2 & B2 withdrawn May 1, 1984
Following a development effort that began in the summer of 1969, the IBM 3340 disk unit was introduced in March 1973 with an advanced disk technology known as "Winchester."* The first 3340 shipments to customers began in November 1973.
The 3340 featured a smaller, lighter read/write head that could ride closer to the disk surface -- on an air film 18 millionths of an inch thick -- with a load of less than 20 grams. The Winchester disk file's low-cost head-slider structure made it feasible to use two heads per surface, cutting the stroke length in half. The disks, the disk spindle and bearings, the carriage and the head-arm assemblies were incorporated into a removable sealed cartridge called the IBM 3348 Data Module. A track density of 300 tracks per inch and an access time of 25 milliseconds were achieved.
The 3340 offered the optional availability of fixed heads, which provided an average access time of only five milliseconds. It had three types of data modules: 35 megabytes, 70 megabytes, and 70 megabytes of which 0.5 megabyte were accessible with fixed heads.
Two-to-four 3340 drives could be attached to the IBM System/370 Model 115 processor -- which had been announced concurrently with the 3340 -- providing a storage capacity of up to 280 million bytes.
* Some observers have noted that the 3340 was known as "Winchester" because its development engineers called it a "30-30" (its two spindles each had a disk capacity of 30 megabytes), the common name of a rifle manufactured by the Winchester Company. Kenneth E. Haughton, who led the 3340 development effort, is reported to have said: "If it's a 30-30, then it must be a Winchester." A new direction
At IBM, we've put our heads together to bring you something new and different in direct access storage devices ... something that utilizes an innovative design approach to give you new data reliability, flexibility, and performance at a price in line with your data processing budget.
It's the IBM 3340 Direct Access Storage Facility, a growth file for those currently operating with IBM 2311s and 2314s. The 3340's innovative design approach is incorporated in its storage media, the IBM 3348 Data Modules. Resembling the familiar disk packs used with other IBM storage devices, the 3348 Data Module is the disk pack's technological successor. For the 3348 contains not only the disk surfaces used for data recording, but the read/write heads and access arms as well.
A happy combination
Why all in one? Because combining them into a single integrated unit can give you greater data reliability than you may have thought possible to achieve with a disk storage device. That's because the write head that records the data on the 3340's disk surfaces is always the read head that reads the data back into your computer. Thus, problems resulting from mistracking due to minute read/write head misalignments are no longer a factor. It is this new Data Module design concept that gives the 3340 greater data reliability and configuration flexibility than offered by any other IBM disk storage unit.
The 3340 also includes several other outstanding features that enhance its read/write reliability. Error correction code in the controller can automatically correct a single loss of data up to three bits long in any data record. Detailed error logging procedures also are included that can help detect potential problems in time for your IBM Customer Engineer to correct them before they become serious.
Advanced features like these give the 3340 the reliability you need to put your critical applications online ... with confidence.
Easy growth at any time
The 3340's range of flexibility in storage capacity is the result of two sizes in Data
Model 35 - 34.9 million bytes, and
Model 70 - 69.8 million bytes.
Both Data Modules are interchangeable and can be used on the same drive without modification. Thus, you can configure your disk subsystem to match your current needs ... and as these needs change, you simply increase the size of the Data Modules to arrive at the desired capacity. It's really simple to keep up with changing storage requirements when you have an IBM 3340!
Performance belies its cost
The performance of the 3340 more than measures up to its advanced design features. In fact, present users of 2311s and 2814s can now move into a level of disk performance that was previously available to them only with IBM's super disk system, the 3330-series. And they can get this kind of performance without having to pay for more storage capacity than they actually need. Check these performance characteristics:
Average seek time (MS)
Average latency (MS)
Data rate (KB/sec.)
Note how much more performance the 3340 offers over that of the 2314. Take a look, too, at how well it stacks up against the 3330. This chart, better than words, indicates the kind of performance you can expect from this outstanding disk file. In fact, in the average computer installation, the 3340 should provide performance very close to that of a 3330... at a price well within the budget range of 2311 and 2314 users.
Rotation Position Sensing (RPS) also is available as an optional feature to boost system throughput. On a 3340 equipped with RPS, one drive can be reading or writing and all other drives in the subsystem can be simultaneously seeking or searching. This capability can significantly enhance system performance, particularly for those systems utilizing large disk subsystems and a high degree of multiprogramming.
Operation is extra easy
The IBM 3340 is probably the easiest-to-operate disk storage device you'll encounter.
To mount a 3348 Data Module, you simply place it in the drive. Its cover need not be removed, nor must it be attached to the drive like previous IBM disk subsystems.
Once the Module is in place, the entire mounting operation is handled automatically by the drive itself. This can result in considerable savings in operator time as well as better utilization of your computing resources.
The particular model being used is automatically sensed and recognized by the 3340. This eliminates need for either the computer operator or the programmer to specify the model in use, and, generally, no program changes are required to accommodate the various models.
Once the disks are brought up to speed, the 3340 is ready for processing to begin. Time for the entire mounting operation: less than 20 seconds!
Use it with all VS System/370s
The 3340 can be used with all System/370 models utilizing DOS/VS, OS/VS1, or Release 2 of 05/ VS2. It's economical enough to fit into the plans of the smallest System/370 user, yet it offers more than enough performance to function efficiently with the models at the top of the line. The new file uses the same integrated attachments as the 3330.
Configuration flexibility
With System/370 Models 115 and 125, the 3340 is directly attached, while with the Model 135, it attaches to the 3330/3340 Integrated File Adapter (IFA). With the Model 145, attachment is through either the Integrated Storage Control (ISC) feature or the 3345 Storage and Control Frame Models 3, 4, and 5. With Model 158 or 168 attachment is through the ISC. In addition, the 3340 can attached to all VS System/370s the Model 135 up via the 3830 Storage Control Model 2.
Also on the Model 135 and larger VS System/370s, a new intermix capability permits 3340s and 3330s to be used together on the same attachment. And with these same systems, use of the optional String Switch Feature allows 3340 strings consisting of up to eight drives each to be manually or dynamically switched between any two attachments. Under OS/VS, the optional 32 Drive Expansion Feature increases to 32 the number of drives that can be attached to the 3830 Model 2 or the Model 145's ISC. Also with this feature, the Model 158 and 168 ISCs can control up to 64 drives. These features and channel switches can be used together to provide large storage pools with high subsystem availability.
Get ahead of the pack
Just as System/370 with virtual storage has opened up new application areas that demand more performance and reliability from a direct access storage subsystem, so, too, does the 3340 offer a file that's particularly suited to this advanced computing environment.
The 3340 brings 3330-like performance into the price realm and capacity range of the 2311 and 2314 user. Performance enough to meet the demands of increased multiprogramming, paging, and online applications. Capacity enough to put the bulk of your direct access files online, thus making your data readily accessible, reducing pack changing, and building a firm foundation for your advanced applications.
Now's the time to move up to the IBM 3340 Direct Access Storage Facility. We've gotten our heads together and put it ahead of the pack.


IBM 3330

The IBM 3330 Direct Access Storage Facility, code-named Merlin, was introduced in June 1970 for use with the IBM System/370 and the IBM System 360/195. Its removable disk packs held 100 MB (404x19x13,030 bytes) (the 1973 Model 11 featured IBM 3336-11 Disk Packs that held 200 MB (808x19x13,030 bytes)). Access time was 30 ms and data transferred at 806 kB/s. A major advance introduced with the 3330 was the use of error correction, which made the drives more reliable and reduced costs because small imperfections in the disk surface could be tolerated. The circuitry could correct error bursts up to 11 bits long. The 3330 was withdrawn in 1983.



IBM 2310

The IBM 2310 Removable Cartridge Drive was announced in 1964 with the IBM 1800 and then in 1965 with the IBM 1130; it likely first shipped with the 1130 in late 1965.It could store 512,000 words (1,024,000 bytes) on an IBM 2315 cartridge. A single 14-inch (360 mm) oxide-coated aluminum disk spun in a plastic shell with openings for the read/write arm and two heads.


IBM 2314/2319

The IBM 2314 Disk Access Storage Facility was introduced on April 22, 1965, one year later after the System/360 introduction. It was used with the System/360 and the System/370 lines. With Two Channel Switch feature it could interface with two 360/370 channels. The 2314 Disk access mechanism was similar to the 2311, but further recording improvements allowed higher data density. The 2314 stored 29,176,000 characters (200×20×7294 bytes per track) on a single removable IBM 2316 disk pack which was similar in design to the 1316 but was taller as a result of increasing the number of disks from six to eleven. The 2316 disk pack containing the eleven 14-inch (360 mm) diameter disks yielded 20 recording surfaces. The drive access consisted of 20 individual R/W heads mounted on a common actuator which was moved in and out hydraulically and mechanically detented at the desired track before reading or writing occurred. Each recording surface had 200 tracks. Access time was initially the same as the 2311, but later models were faster as a result of improvements made in the hydraulic actuator. Data transfer rate was doubled to 310 kB/s.
The original Model 1 consisted of the 2314 control unit, a 2312 single drive module, and two 2313 four drive modules for a total of 9 disk drives. Only eight drives of the nine were available to the user at any one time. The ninth drive was there for a spare for the user and could also be worked on 'offline' by a Field Engineer while the other drives were in use by the customer. Each of the nine drives were mounted in individual drawers that were unlatched and pulled out to access the Disk Pack. Because of their appearance they picked up the nickname of 'Pizza Ovens'
Other 2314 Models came later: 2314 Model A with combinations of one to nine drives. 2314 Model B with 2319 disk drives were available in three, six and nine drive models. A 2844 Control Unit could be added to the 2314 Control Unit which allowed two S/360 Channels simultaneous access to two separate disk drives in the Storage Facility.


IBM 2311

The IBM 2311 Direct Access Storage Facility was introduced in 1964 for use throughout the System/360 series. It was also available on the IBM 1130 and (using the 2841 Control Unit) the IBM 1800. The 2311 mechanism was largely identical to the 1311, but recording improvements allowed higher data density. The 2311 stored 7.25 megabytes on a single removable IBM 1316 disk pack (the same type used on the IBM 1311) consisting of six platters that rotated as a single unit. Each recording surface had 200 tracks plus 3 optional tracks which could be used as alternatives in case faulty tracks were discovered. Average seek time was 85 ms. Data transfer rate was 156 kB/s.
The 2311 had 10 individual R/W heads mounted on a common actuator which was moved in and out hydraulically and mechanically detented at the desired track before reading or writing occurred. The 2311 was organized into cylinders, tracks, and records. (A cylinder referred to all surfaces the same track on each of the 5 platters.) Record 0 was reserved for timing.
Because the 2311 was to be used with a wide variety of computers within the 360 product line, its electrical interconnection was standardized. This created an opportunity for other manufacturers to sell plug compatible disk drives for use with IBM computers and an entire industry was born.


IBM 2305

The IBM 2305 Direct Access Storage Facility was a fixed-head disk drive originally announced in 1970 to connect to the 360/85 and 360/195 using the IBM 2880 Block Multiplexor Channel. The 2305-1 ran at 3.0 MB/second when attached using the 2-byte channel interface, and the larger 2305-2 ran at 1.5 MB/second.
The 2305/2835 Storage Facility became popular with the System/370, and used as the paging device of choice, for systems 155-2, 158, 165-2 and 168. This was particularly true at IBM internal data centers where obsolete equipment was often all that was available. When floor space was not at a premium, the fixed head storage devices gave paging performance comparable to the alternative of using only the small amount of disk space located under one seek position of a standard disk drive and leaving the rest of the volume empty, which was a common practice in high transaction environments such as airline reservation systems, for paging and high volatility data storage.


IBM 1311 Disk Storage Drive

The IBM 2302 was the S/360 version of the 1302, with track formatting in accordance with S/360 DASD architecture rather than 7000 series architecture.


IBM 1311

The IBM 1311 Disk Storage Drive was announced on October 11, 1962 and was designed for use with several medium-scale business and scientific computers. The 1311 was about the size and shape of a top-loading washing machine and stored 2 million characters on a removable IBM 1316 disk pack.Seven models of the 1311 were introduced during the 1960s. They were withdrawn during the early 1970s.
Models of the 1311 disk drive:
  1. Had to be drive 1 on an IBM 1440, IBM 1460, or IBM 1240 system. Contained the controller and could control up to 4 – Model 2 drives. Introduced October 11, 1962. Withdrawn February 8, 1971.
  2. Slave drive. Could have any special feature incorporated that the master drive (drive 1) had incorporated. Introduced October 11, 1962. Withdrawn January 6, 1975.
  3. Had to be drive 1 on an IBM 1620 or IBM 1710 system. Contained the controller and could control up to 3 – Model 2 drives. Did not support any special features. Introduced October 11, 1962. Withdrawn May 12, 1971.
  4. Had to be drive 1 on an IBM 1401 system. Contains the controller and can control up to 4 – Model 2 drives. Introduced October 11, 1962. Withdrawn February 8, 1971.
  5. Had to be drive 1 on an IBM 1410, IBM 7010, or IBM 7740 system. Contained the controller and could control up to 4 – Model 2 drives. Direct Seek came as standard on this model. Introduced January 7, 1963. Withdrawn May 12, 1971.
  6. No information available, probably a master drive (drive 1). Introduced March 5, 1968. Withdrawn February 2, 1971.
  7. No information available, probably a master drive (drive 1). Introduced March 5, 1968. Withdrawn February 2, 1971.
The optional special features were
  • Direct Seek: Without this option every seek returned to track zero first.
  • Scan Disk: Automatic rapid search for identifier or condition.
  • Seek Overlap: Allowed a seek to overlap ONE read or write and any number of other seeks.
  • Track Record: Increased the capacity of the disk by writing ONE large record per track instead of using sectors.
Drive 1 (the master drive: models 1, 3, 4, and 5) was about a foot wider than the other drives (the slave drives: model 2), to contain extra power supplies and the control logic.
Each IBM 1316 Disk Pack was 4 inches (100 mm) high, weighed 10 pounds (4.5 kg) and contained six 14-inch (360 mm) diameter disks, yielding 10 recording surfaces (the outer surfaces were not used). The 10 individual read/write heads were mounted on a common actuator within the disk drive which was moved in and out hydraulically and mechanically detented at the desired track before reading or writing occurred. The disks spun at 1500 rpm. Each recording surface had 100 tracks with 20 sectors per track. Each sector stored 100 characters. The disk pack was covered with a clear plastic shell and a bottom cover when not in use. A lifting handle in the top center of the cover was rotated to release the bottom cover. Then the top of the 1311 drive was opened and the plastic shell lowered into the disk-drive opening (assuming it was empty). The handle was turned again to lock the disks in place and release the plastic shell, which was then removed and the drive cover closed. The process was reversed to remove a disk pack.


IBM 1302

The IBM 1302 Disk Storage Unit was introduced in September 1963. Improved recording quadrupled its capacity over that of the 1301, to 117 million 6-bit characters per module. Average access time was 165 ms and data could be transferred at 180 K characters/second, more than double the speed of the 1301. A second arm accessed a separate group of 250 tracks. As with the 1301, there was a Model 2 with twice the capacity. The IBM 1302 Model 1 leased for $5,600 per month or could be purchased for $252,000. Prices for the Model 2 were $7,900 per month or $355,500 to purchase. The IBM 7631 controller cost an additional $1,185 per month or $56,000 to purchase. The 1302 was withdrawn in February 1965.


IBM 1301

The IBM 1301 Disk Storage Unit was announced on June 2, 1961. It was designed for use with the IBM 7000 series mainframe computers and the IBM 1410. The 1301 stored 28 million characters on a single module (25 million with the 1410). Each module had 20 large disks and 40 recording surfaces, with 250 tracks per surface. The 1301 Model 1 had one module, the Model 2 had two modules, stacked vertically. The disks spun at 1800 rpm. Data was transferred at 90,000 characters per second.
A major advance over the IBM 350 and IBM 1405 was the use of a separate arm and head for each recording surface, with all the arms moving in and out together like a big comb. This eliminated the time needed for the arm to pull the head out of one disk and move up or down to a new disk. Seeking the desired track was also faster since, with the new design, the head would usually be somewhere in the middle of the disk, not starting on the outer edge. Maximum access time was reduced to 180 milliseconds.
The 1301 also featured heads that were aerodynamically designed to fly over the surface of the disk on a thin layer of air. This allowed them to be much closer to the recording surface, which greatly improved performance.
The 1301 was connected to the computer via the IBM 7631 File Control. Different models of the 7631 allowed the 1301 to be used with a 1410 or 7000 series computer or shared between a 7000 and a 1410 or between two 7000's.
The IBM 1301 Model 1 leased for $2,100 per month or could be purchased for $115,500. Prices for the Model 2 were $3,500 per month or $185,000 to purchase. The IBM 7631 controller cost an additional $1,185 per month or $56,000 to purchase. All models were withdrawn in 1970.


IBM 1405

The IBM 1405 Disk Storage Unit was announced by 1961 and was designed for use with the IBM 1401 series, medium scale business computers. The 1405 stored 10 million characters on a single module. Each module had 25 large disks, yielding 50 recording surfaces. The disks spun at 1200 rpm. The Model 1 had one module, the Model 2 had two modules, stacked vertically. Each recording surface had 200 tracks and 5 sectors per track. Data was read or recorded at 22,500 characters per second. A single arm moved in and out and up and down. Access time ranged from 100 to 800 milliseconds (Model 2).


IBM 355

The IBM 355 was announced on September 14, 1956 as an addition to the popular IBM 650. It used the same mechanism as the IBM 350 and stored 6 million 7-bit decimal digits.Data was transferred to and from the IBM 653 magnetic core memory, an IBM 650 option that stored just sixty 10-digit words, enough for a single sector of disk or tape data.


IBM 353

The IBM 353 used on the IBM 7030, was similar to the IBM 1301, but with a faster transfer rate. It had a capacity of 2,097,152 (221) 64-bit words (two 32 data bit half words each with 7 ECC bits) and transferred 125,000 words per second. Unlike the flying heads of the 1301, the 353 used the older head design of the IBM 350 RAMAC.


IBM 350

The IBM 350 disk storage unit, the first disk drive, was announced by IBM as a component of the IBM 305 RAMAC computer system on September 13, 1956.Simultaneously a very similar product, the "IBM 355 Random Access Memory" was announced for the IBM 650 computer system. RAMAC stood for "Random Access Method of Accounting and Control."
Its design was motivated by the need for real time accounting in business. The 350 stored 5 million 7-bit (6-bits plus 1 odd parity bit) characters (about 4.4 megabytes). It had fifty 24-inch (610 mm) diameter disks with 100 recording surfaces. Each surface had 100 tracks. The disks spun at 1200 RPM. Data transfer rate was 8,800 characters per second. An access mechanism moved a pair of heads up and down to select a disk pair (one down surface and one up surface) and in and out to select a recording track of a surface pair. Several improved models were added in the 1950s. The IBM RAMAC 305 system with 350 disk storage leased for $3,200 per month. The 350 was officially withdrawn in 1969

The 350's cabinet was 60 inches (152 cm) long, 68 inches (172 cm) high and 29 inches (74 cm) deep. IBM had a strict rule that all its products must pass through a standard 29.5 inch (75 cm) doorway. Since the 350's platters were mounted horizontally, this rule presumably dictated the maximum diameter of the disks.
Currie Munce, research vice president for Hitachi Global Storage Technologies (which has acquired IBM's storage business), stated in a Wall Street Journal interview that the RAMAC unit weighed over a ton, had to be moved around with forklifts, and was delivered via large cargo airplanes. According to Munce, the storage capacity of the drive could have been increased beyond five megabytes, but IBM's marketing department at that time was against a larger capacity drive, because they didn't know how to sell a product with more storage.
In 2002, the Magnetic Disk Heritage Center began restoration of an IBM 350 RAMAC in collaboration with Santa Clara University. In 2005, the RAMAC restoration project relocated to the Computer History Museum where efforts to restore the drive for public display continue


History of hard disk drives

IBM in 1953 recognized the immediate application for what it termed a "Random Access File" having high capacity, rapid random access at a relatively low cost After considering several alternative technologies such as wire matrices, rod arrays, drums, drum arrays, etc, the engineers at IBM San Jose invented the disk drive. The disk drive created a new level in the computer data hierarchy, then termed Random Access Storage but today known as secondary storage, less expensive and slower than main memory (then typically drums) but faster and more expensive than tape drives
The commercial usage of hard disk drives began in 1956 with the shipment of an IBM 305 RAMAC system including IBM Model 350 disk storage.
Compared to modern disk drives, early hard disk drives were large, sensitive and cumbersome devices, more suited to use in the protected environment of a data center than in an industrial environment, office or home. Disk media was nominally 8-inch or 14-inch platters, which required large equipment rack enclosures. Drives with removable media resembled washing machines in size and often required high-current or a three-phase power supply due to the large motors they used. Hard disk drives were not commonly used with microcomputers until after 1980, when Seagate Technology introduced the ST-506, the first 5.25-inch hard drives, with a formatted capacity of 5 megabytes.
The capacity of hard drives has grown exponentially over time. With early personal computers, a drive with a 20 megabyte capacity was considered large. During the mid-1990s the typical hard disk drive for a PC had a capacity of about 1 GBAs of July 2010, desktop hard disk drives typically have a capacity of 500 to 1000 gigabytes, while the largest-capacity drives are 3 terabytes


Semiconductor Technology

8:40 AM 0 Comments

A semiconductor is any material that promotes the flow of electricity. The advent of semiconductor technology in the 1970s gave rise to today's random access memory. The first company to create, manufacture and market an economical semiconductor core memory was Intel. The company began work in 1968 and introduced a 64-bit RAM chip in 1969. In the same year, Intel released a 256-bit chip, the first commercial use of a silicone-based semiconductor for computer memory. For the last 40 years, semiconductors have been the basis for all RAM technology


Magnetic Core Memory

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Magnetic core memory, the earliest form of random access memory, was developed in the late 1940s and early 1950s. This form of memory has metallic wires threaded through magnetic rings and used polarity to store information. As with drum memory, magnetic core memory was short-lived, but the word "core" survived.


The First Computer Memory

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The first electric computer (previous computers were mechanical) was invented between 1939 and 1942 by John Atanasoff and Clifford Berry. The memory used was in the form of two rotating drums that held an electrical charge. The idea of using charged, rotating drums was short-lived as the invention of core memory was being developed in the 1940s. The Atanasoff-Berry computer was also the first electrical device to use binary code---information in the form of ones and zeros


The History of Random Access Memory

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RAM, or random access memory, is temporary storage space for data to be used by a computer's processor, unlike the hard drive, which permanently stores data to be retrieved later. As of 2010, RAM has taken three distinct leaps in development.


Reduced instruction set computing

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In the mid-1980s to early-1990s, a crop of new high-performance Reduced Instruction Set Computer (RISC) microprocessors appeared, influenced by discrete RISC-like CPU designs such as the IBM 801 and others. RISC microprocessors were initially used in special-purpose machines and Unix workstations, but then gained wide acceptance in other roles.
In 1986, HP released its first system with a PA-RISC CPU. The first commercial RISC microprocessor design was released either by MIPS Computer Systems, the 32-bit R2000 (the R1000 was not released) or by Acorn computers, the 32-bit ARM2 in 1987.The R3000 made the design truly practical, and the R4000 introduced the world's first commercially available 64-bit RISC microprocessor. Competing projects would result in the IBM POWER and Sun SPARC architectures. Soon every major vendor was releasing a RISC design, including the AT&T CRISP, AMD 29000, Intel i860 and Intel i960, Motorola 88000, DEC Alpha.
As of 2007, two 64-bit RISC architectures are still produced in volume for non-embedded applications: SPARC and Power ISA


Multicore designs

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A different approach to improving a computer's performance is to add extra processors, as in symmetric multiprocessing designs, which have been popular in servers and workstations since the early 1990s. Keeping up with Moore's Law is becoming increasingly challenging as chip-making technologies approach the physical limits of the technology.
In response, the microprocessor manufacturers look for other ways to improve performance, in order to hold on to the momentum of constant upgrades in the market.
A multi-core processor is simply a single chip containing more than one microprocessor core, effectively multiplying the potential performance with the number of cores (as long as the operating system and software is designed to take advantage of more than one processor). Some components, such as bus interface and second level cache, may be shared between cores. Because the cores are physically very close they interface at much faster clock rates compared to discrete multiprocessor systems, improving overall system performance.
In 2005, the first personal computer dual-core processors were announced and as of 2009 dual-core and quad-core processors are widely used in servers, workstations and PCs while six and eight-core processors will be available for high-end applications in both the home and professional environments.
Sun Microsystems has released the Niagara and Niagara 2 chips, both of which feature an eight-core design. The Niagara 2 supports more threads and operates at 1.6 GHz.
High-end Intel Xeon processors that are on the LGA771 socket are DP (dual processor) capable, as well as the Intel Core 2 Extreme QX9775 also used in the Mac Pro by Apple and the Intel Skulltrail motherboard. With the transition to the LGA1366 and LGA1156 socket and the Intel i7 and i5 chips, quad core is now considered mainstream, but with the release of the i7-980x, six core processors are now well within reach.


64-bit designs in personal computers

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While 64-bit microprocessor designs have been in use in several markets since the early 1990s, the early 2000s saw the introduction of 64-bit microprocessors targeted at the PC market.
With AMD's introduction of a 64-bit architecture backwards-compatible with x86, x86-64 (also called AMD64), in September 2003, followed by Intel's near fully compatible 64-bit extensions (first called IA-32e or EM64T, later renamed Intel 64), the 64-bit desktop era began. Both versions can run 32-bit legacy applications without any performance penalty as well as new 64-bit software. With operating systems Windows XP x64, Windows Vista x64, Windows 7 x64, Linux, BSD and Mac OS X that run 64-bit native, the software is also geared to fully utilize the capabilities of such processors. The move to 64 bits is more than just an increase in register size from the IA-32 as it also doubles the number of general-purpose registers.
The move to 64 bits by PowerPC processors had been intended since the processors' design in the early 90s and was not a major cause of incompatibility. Existing integer registers are extended as are all related data pathways, but, as was the case with IA-32, both floating point and vector units had been operating at or above 64 bits for several years. Unlike what happened when IA-32 was extended to x86-64, no new general purpose registers were added in 64-bit PowerPC, so any performance gained when using the 64-bit mode for applications making no use of the larger address space is minimal


32-bit designs

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16-bit designs had only been on the market briefly when 32-bit implementations started to appear.
The most significant of the 32-bit designs is the MC68000, introduced in 1979. The 68K, as it was widely known, had 32-bit registers but used 16-bit internal data paths and a 16-bit external data bus to reduce pin count, and supported only 24-bit addresses. Motorola generally described it as a 16-bit processor, though it clearly has 32-bit architecture. The combination of high performance, large (16 megabytes or 224 bytes) memory space and fairly low cost made it the most popular CPU design of its class. The Apple Lisa and Macintosh designs made use of the 68000, as did a host of other designs in the mid-1980s, including the Atari ST and Commodore Amiga.
The world's first single-chip fully-32-bit microprocessor, with 32-bit data paths, 32-bit buses, and 32-bit addresses, was the AT&T Bell Labs BELLMAC-32A, with first samples in 1980, and general production in 1982 After the divestiture of AT&T in 1984, it was renamed the WE 32000 (WE for Western Electric), and had two follow-on generations, the WE 32100 and WE 32200. These microprocessors were used in the AT&T 3B5 and 3B15 minicomputers; in the 3B2, the world's first desktop supermicrocomputer; in the "Companion", the world's first 32-bit laptop computer; and in "Alexander", the world's first book-sized supermicrocomputer, featuring ROM-pack memory cartridges similar to today's gaming consoles. All these systems ran the UNIX System V operating system.
Intel's first 32-bit microprocessor was the iAPX 432, which was introduced in 1981 but was not a commercial success. It had an advanced capability-based object-oriented architecture, but poor performance compared to contemporary architectures such as Intel's own 80286 (introduced 1982), which was almost four times as fast on typical benchmark tests. However, the results for the iAPX432 was partly due to a rushed and therefore suboptimal Ada compiler.

The ARM first appeared in 1985. This is a RISC processor design, which has since come to dominate the 32-bit embedded systems processor space due in large part to its power efficiency, its licensing model, and its wide selection of system development tools. Semiconductor manufacturers generally license cores such as the ARM11 and integrate them into their own system on a chip products; only a few such vendors are licensed to modify the ARM cores. Most cell phones include an ARM processor, as do a wide variety of other products. There are microcontroller-oriented ARM cores without virtual memory support, as well as SMP applications processors with virtual memory.
Motorola's success with the 68000 led to the MC68010, which added virtual memory support. The MC68020, introduced in 1985 added full 32-bit data and address busses. The 68020 became hugely popular in the Unix supermicrocomputer market, and many small companies (e.g., Altos, Charles River Data Systems) produced desktop-size systems. The MC68030 was introduced next, improving upon the previous design by integrating the MMU into the chip. The continued success led to the MC68040, which included an FPU for better math performance. A 68050 failed to achieve its performance goals and was not released, and the follow-up MC68060 was released into a market saturated by much faster RISC designs. The 68K family faded from the desktop in the early 1990s.
Other large companies designed the 68020 and follow-ons into embedded equipment. At one point, there were more 68020s in embedded equipment than there were Intel Pentiums in PCs. The ColdFire processor cores are derivatives of the venerable 68020.
During this time (early to mid-1980s), National Semiconductor introduced a very similar 16-bit pinout, 32-bit internal microprocessor called the NS 16032 (later renamed 32016), the full 32-bit version named the NS 32032. Later the NS 32132 was introduced which allowed two CPUs to reside on the same memory bus, with built in arbitration. The NS32016/32 outperformed the MC68000/10 but the NS32332 which arrived at approximately the same time the MC68020 did not have enough performance. The third generation chip, the NS32532 was different. It had about double the performance of the MC68030 which was released around the same time. The appearance of RISC processors like the AM29000 and MC88000 (now both dead) influenced the architecture of the final core, the NS32764. Technically advanced, using a superscalar RISC core, internally overclocked, with a 64 bit bus, it was still capable of executing Series 32000 instructions through real time translation.
When National Semiconductor decided to leave the Unix market, the chip was redesigned into the Swordfish Embedded processor with a set of on chip peripherals. The chip turned out to be too expensive for the laser printer market and was killed. The design team went to Intel and there designed the Pentium processor which is very similar to the NS32764 core internally The big success of the Series 32000 was in the laser printer market, where the NS32CG16 with microcoded BitBlt instructions had very good price/performance and was adopted by large companies like Canon. By the mid-1980s, Sequent introduced the first symmetric multiprocessor (SMP) server-class computer using the NS 32032. This was one of the design's few wins, and it disappeared in the late 1980s. The MIPS R2000 (1984) and R3000 (1989) were highly successful 32-bit RISC microprocessors. They were used in high-end workstations and servers by SGI, among others. Other designs included the interesting Zilog Z80000, which arrived too late to market to stand a chance and disappeared quickly.
In the late 1980s, "microprocessor wars" started killing off some of the microprocessors. Apparently, with only one major design win, Sequent, the NS 32032 just faded out of existence, and Sequent switched to Intel microprocessors.
From 1985 to 2003, the 32-bit x86 architectures became increasingly dominant in desktop, laptop, and server markets, and these microprocessors became faster and more capable. Intel had licensed early versions of the architecture to other companies, but declined to license the Pentium, so AMD and Cyrix built later versions of the architecture based on their own designs. During this span, these processors increased in complexity (transistor count) and capability (instructions/second) by at least three orders of magnitude. Intel's Pentium line is probably the most famous and recognizable 32-bit processor model, at least with the public at large.


12-bit designs

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The Intersil 6100 family consisted of a 12-bit microprocessor (the 6100) and a range of peripheral support and memory ICs. The microprocessor recognised the DEC PDP-8 minicomputer instruction set. As such it was sometimes referred to as the CMOS-PDP8. Since it was also produced by Harris Corporation, it was also known as the Harris HM-6100. By virtue of its CMOS technology and associated benefits, the 6100 was being incorporated into some military designs until the early 1980s


8-bit designs

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The Intel 4004 was followed in 1972 by the Intel 8008, the world's first 8-bit microprocessor. The 8008 was not, however, an extension of the 4004 design, but instead the culmination of a separate design project at Intel, arising from a contract with Computer Terminals Corporation, of San Antonio TX, for a chip for a terminal they were designing the Datapoint 2200 — fundamental aspects of the design came not from Intel but from CTC. In 1968, CTC's Austin O. “Gus” Roche developed the original design for the instruction set and operation of the processor. In 1969, CTC contracted two companies, Intel and Texas Instruments, to make a single-chip implementation, known as the CTC 1201In late 1970 or early 1971, TI dropped out being unable to make a reliable part. In 1970, with Intel yet to deliver the part, CTC opted to use their own implementation in the Datapoint 3300, using traditional TTL logic instead (thus the first machine to run “8008 code” was not in fact a microprocessor at all!). Intel's version of the 1201 microprocessor arrived in late 1971, but was too late, slow, and required a number of additional support chips. CTC had no interest in using it. CTC had originally contracted Intel for the chip, and would have owed them $50,000 for their design work To avoid paying for a chip they did not want (and could not use), CTC released Intel from their contract and allowed them free use of the desig Intel marketed it as the 8008 in April, 1972, as the world's first 8-bit microprocessor. It was the basis for the famous "Mark-8" computer kit advertised in the magazine Radio-Electronics in 1974.

The 8008 was the precursor to the very successful Intel 8080 (1974), which offered much improved performance over the 8008 and required fewer support chips, Zilog Z80 (1976), and derivative Intel 8-bit processors. The competing Motorola 6800 was released August 1974 and the similar MOS Technology 6502 in 1975 (designed largely by the same people). The 6502 rivaled the Z80 in popularity during the 1980s.
A low overall cost, small packaging, simple computer bus requirements, and sometimes the integration of extra circuitry (e.g. the Z80's built-in memory refresh circuitry) allowed the home computer "revolution" to accelerate sharply in the early 1980s. This delivered such inexpensive machines as the Sinclair ZX-81, which sold for US$99.
The Western Design Center, Inc. (WDC) introduced the CMOS 65C02 in 1982 and licensed the design to several firms. It was used as the CPU in the Apple IIe and IIc personal computers as well as in medical implantable grade pacemakers and defibrilators, automotive, industrial and consumer devices. WDC pioneered the licensing of microprocessor designs, later followed by ARM and other microprocessor Intellectual Property (IP) providers in the 1990s.
Motorola introduced the MC6809 in 1978, an ambitious and thought-through 8-bit design source compatible with the 6800 and implemented using purely hard-wired logic. (Subsequent 16-bit microprocessors typically used microcode to some extent, as CISC design requirements were getting too complex for purely hard-wired logic only.)
Another early 8-bit microprocessor was the Signetics 2650, which enjoyed a brief surge of interest due to its innovative and powerful instruction set architecture.
A seminal microprocessor in the world of spaceflight was RCA's RCA 1802 (aka CDP1802, RCA COSMAC) (introduced in 1976), which was used onboard the Galileo probe to Jupiter (launched 1989, arrived 1995). RCA COSMAC was the first to implement CMOS technology. The CDP1802 was used because it could be run at very low power, and because a variant was available fabricated using a special production process (Silicon on Sapphire), providing much better protection against cosmic radiation and electrostatic discharges than that of any other processor of the era. Thus, the SOS version of the 1802 was said to be the first radiation-hardened microprocessor.
The RCA 1802 had what is called a static design, meaning that the clock frequency could be made arbitrarily low, even to 0 Hz, a total stop condition. This let the Galileo spacecraft use minimum electric power for long uneventful stretches of a voyage. Timers and/or sensors would awaken/improve the performance of the processor in time for important tasks, such as navigation updates, attitude control, data acquisition, and radio communication.