Software:History of IBM CKD Controllers

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Main article: Count key data

Beginning with its 1964 System/360 announcement, IBM's mainframes initially accessed count key data (CKD) subsystems via a channel connected to separate Storage Control Units (SCUs) with attached direct-access storage devices (DASD), typically hard disk drives. This practice continued in IBM's larger mainframes thru IBM Z; however low end systems generally used lower cost integrated attachments where the function of the SCU was combined with that of the channel, typically called an Integrated File Adapter.

The System/360 selector channel was followed by the System/370 block multiplexor channel which could operate as a selector channel to allow attachment of legacy subsystems.

The SCU evolved into a Director and Controller, the latter typically labelled an "A-unit" (or A-Box") with the controller and at least one DASD physically in an A-unit. An Integrated Storage Control (ISC) is a Director within the cabinet of an IBM System. A Director could attach from one to four A-units. One or more conventional DASD, now labeled a "B-unit" could attach to an A-unit

The following sections list in order of announcement IBM mainframe CKD storage controls, categorized as conventional storage controls, director type storage controls and integrated controls attaching an A-unit.

Chronological summary

CKD storage controls in chronological order[1]
Controller
Manual[lower-alpha 1] 		Announcement
Date[lower-alpha 2] 		Comment
2820 SCU A22-6895[2] 4/7/1964 used only with the IBM 2301 drum
2841 SCU A26-5988-0[3] 4/7/1964
2314 DASF A26-3599[4] 4/23/1965 Bundled SCU with 9 drives, similar to 2841
System/360 Model 25 DAC A24-3510[5] 1/4/1968
2314-A1 SCU A26-3599[4] 9/1969 est.[6] Unbundled 2314 DASF, SCU similar to 2841
2844 Aux SCU with 2314 A26-3599[4] 1968 est.[lower-alpha 3] provides dual path, similar to 2841
2835-1,2 SCUs GA26-1589[7] 1/28/1970 similar to with parallel read channels
3830-1 SCU GA26-1592[8] 6/30/1970
System/370 Model 145 IFA A26-3599[4] 9/23/1970
2314-B1 SCU A26-3599[4] 12/14/1970 For 2319B DASD, similar to 2841
3830-2 SCU GA26-1617[9] Aug 1972 single director
Integrated Storage Control Unit GA26-1620 8/2/1972 A repackaged 3830-2
S/370 , -2 {{not a typo|3330/3 ment 10/4/1972
[[#IBM115DDA|S/370 , -2, 125-0} 340/3344 Direct Disk A 3/17/1973
3830-3 SCU and
Integrated Storage Controller with Staging Adapter		 GA32-0036 10/9/1974 single director, used with 3850 MSS
S/370 138 Integrated File Adapter GA24-3632 6/30/1976
[[#IBM43x1DA| DASD Adapter for 3340/3344} 9.[10]

S/370 138 Integrated File Adapter

One or two 3330 or 3340 A-units can be attached to the Integrated File Adapter of the S/370 Model 138. Up to three appropriate B-units may be attached to each A-unit. If 3344 B-units are installed, they may only installed in the first of the two possible strings with up to three 3340 and/or 3344 B-units in any combination.[11]

4321/4331 DASD Adapter for 3340/3344

One or two DASD adapters are available (depending upon model) for attachment of one 3340 A-unit and with up to three additional 3340 or 3344 B-units providing up to eight devices. String Switch feature in the 3340 A-unit allows sharing of DASD with another IBM processor or director that supports the A-units and string switching.[10]

4361 DASD Adapter for 3340/3344

Up to four 3340 A-units can be attached to an optional DASD Adapter; to each 3340 A-unit can be attached from one to three 3340 B-units or 3344 B-units for a total of 32 DASD in four strings of eight. String Switch feature in the 3340 A-unit allows sharing of DASD with another IBM processor or director that supports the A-units and string switching.[10]

Notes

  1. ↑ Manual numbers are generic; links are to the latest version as indicated by the highest dash number found on line.
  2. ↑ Unless otherwise noted dates are from IBM's Storage product profiles or Mainframes product profiles
  3. ↑ This model number appears in Datamation’s December 1968 edition

References

  1. ↑ The tables within each section are extracted from IBM System/370 Reference Summary GX20-1850-7, IBM Corp., February 1989, with System/360 SCUs information added from reference manuals.
  2. ↑ IBM System/360 Component Descriptions - 2820 Storage Control and 2301 Drum Storage. IBM. September 1968. A22-6895-2. https://bitsavers.org/pdf/ibm/2820/A22-6895-2_2820_2301_Component_Descr_Sep69.pdf. 
  3. ↑ IBM System/360 Component Descriptions - 2841 Storage Control Unit, 2302 Disk Storage, Models 3 and 4, 2311 Disk Storage Drive, 2321 Data Cell Drive, Model 1, 7320 Drum Storage. IBM. A26-5988-0. https://bitsavers.org/pdf/ibm/2841/A26-5988-0_2841_2311_2321_7320_Descr.pdf. 
  4. ↑ 4.0 4.1 4.2 4.3 4.4 IBM System/360 Component Descriptions 2314 Direct Access Storage Facility and 2844 Auxiliary Storage Control. IBM. November 1971. GA26-3599-6. https://bitsavers.org/pdf/ibm/2844/GA26-3599-6_2314_2844_Component_Description_Nov71.pdf. 
  5. ↑ IBM System/360 Model 25 Functional Characteristics (First ed.). IBM. January 1968. A24-3S10-0. https://bitsavers.org/pdf/ibm/360/functional_characteristics/A24-3510-0_360-25_funcChar_Jan68.pdf. 
  6. ↑ "multi-disc drive". Datamation: 206. September 1969. "IBM is now offering from one to eight active disc drives for its 2314 direct access storage facility". 
  7. ↑ Reference Manual for IBM 2835 Storage Control and IBM 2305 Fixed Head Storage Module. IBM. August 1971. GA26-1589-2. https://bitsavers.org/pdf/ibm/dasd/2305/GA26-1589-2_2835_Storage_Control_and_2305_Fixed_Head_Storage_Module_Aug71.pdf. 
  8. ↑ Reference Manual for IBM 3830 Storage Control Model 1 and IBM 3330 Disk Storage. IBM. November 1976. GA26-1592-5. https://bitsavers.org/pdf/ibm/3830/GA26-1592-5_Reference_Manual_for_IBM_3830_Storage_Control_Model_1_and_IBM_3330_Disk_Storage_Nov76.pdf. 
  9. ↑ Reference Manual for IBM 3830 Storage Control Model 2. IBM. April 1977. p. 11. GA26-1592-5. https://vtda.org/docs/computing/IBM/Mainframe/Hardware/DataStor/GA26-1617-5_IBM3830StorageControlModel2_Ref_Apr77.pdf. 
  10. ↑ 10.0 10.1 10.2 Universal Sales Manual Hardware Products. IBM. February 15, 1994. 
  11. ↑ IBM System/370 Input/Output Systems Configurator. IBM. April 1988. GA22-7002-27. https://bitsavers.org/pdf/ibm/370/GA22-7002-27_IBM_System_370_Input_Output_Configurator_Apr88.pdf. Retrieved January 1, 2016. 

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