IBM 2361 Large Capacity Storage

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The IBM 2361 Large Capacity Storage is a component of the IBM System/360 models 50,[1] 65[2] (when not being used as a multiprocessor), and 75[3] computers. Storage is implemented using magnetic cores; the cycle time is 8 microseconds and the access time is 3.6 microseconds. This component was also called IBM 2361 Core Storage, IBM 2361 Large Core Storage, and LCS.

In addition to its use on System/360, the IBM 2361 was also provided to NASA for use on their IBM 7094 real-time system.

There are two models of the IBM 2361: model 1 has 1,048,576 bytes and model 2 has 2,097,152 bytes.

The IBM 2361 could be shared between two System/360 computers. When sharing is between two model 50s, two model 65s, two model 75s, or a model 65 and a model 75, the two systems must have the same amount of main storage. When one of the sharing systems is a model 50 and the other a model 65 or model 75, the model 50 may have less main storage than the model 65 or model 75.[4]

If a system contained an even number of IBM 2361 components and at least one model 65 or model 75 processor, the IBM 2361s could be interleaved to improve sequential access time. With interleaving, the first 64-bit word is contained in the first IBM 2361, the second in the second, the third in the first, and so forth. When doing sequential access, one IBM 2361 could complete its cycle while the other IBM 2361 was starting the next cycle.


  1. ^ IBM (1967), IBM System/360 Model 50 Functional Characteristics (PDF), Second Edition, A22-6898-1. 
  2. ^ IBM (September 1968), IBM System/360 Model 65 Functional Characteristics (PDF), Fourth Edition, A22-6884-3. 
  3. ^ IBM, IBM System/360 Model 75 Functional Characteristics (PDF), A22-6889-0. 
  4. ^ IBM, IBM System/360 System Summary (PDF), GA22-6810-12. 

External links[edit]

  • IBM, IBM System/360 Operating System Introduction to Main Storage Hierarchy Support for IBM 2361 Models 1 and 2, GC27-6942-2. 
  • Large core storage utilization in theory and practice A research report on the IBM 2361 at NASA from IBM Houston.
  • Computers in Spaceflight: the NASA Experience Describes use of the LCS before the availability of virtual memory.
  • Lauer, Hugh (1967), "Bulk core in a 360/67 time-sharing system", 1967 Fall Joint Computer Conference, AFIPS Conference Proceedings, Volume 31, Academic Press, pp. 601–609.  Describes use of the IBM 2361 on a simplex System/360 model 67.