IBM 2365 Processor Storage
The IBM 2365 Processor Storage was a component of the IBM System/360 models 65[1], 67[2], 75[3] and 85[4] computers. Storage was implemented using magnetic cores, and the cycle time was 750 nanoseconds. Memory fetch and store were 8 bytes at a time. Including the parity bits, this meant that a storage word was 72 bits wide. The IBM 2365 model 1 contained 131,072 bytes of memory; all other models contained 262,144 bytes. The model 2 could be converted in the field to a model 13.
All models other than the model 1 consisted of two memory stacks. Addressing for the stacks was interleaved, so the first 64-bit word was in one stack, the second in the other stack, and so forth. This improved performance when doing sequential access.
The various models were used as follows:
- Model 1 was used on the System/360 model 65 when not used as a multiprocessor.
- Model 2 was used on the System/360 models 65 (when not used as a multiprocessor) and 67-1.
- Model 3 was used on the System/360 model 75.
- Model 5 was used on the System/360 model 85.
- Model 12 was used on the System/360 model 67-2.
- Model 13 was used on the System/360 model 65 when used as a multiprocessor.
The IBM 2365 model 5 was special because the System/360 model 85 was a 128-bit machine, unlike the other System/360 models which supported the IBM 2365, all of which were 64-bit machines. On the System/360 model 85, the IBM 2365 model 5 operated with a cycle time of 1040 nanoseconds, and two or four of them were required. Because the System/360 model 85 CPU was so much faster than memory, if there were two IBM 2365 model 5 components they were two-way interleaved, and if there were four IBM 2365 model 5 components they were four-way interleaved. Because the IBM 2365 model 5 was internally two-way interleaved, sequential 128-bit memory operations issued by the System/360 model 85 CPU would traverse all the memory components before cycling back to the first.
References
- ^ IBM (September 1968). IBM System/360 Model 65 Functional Characteristics (PDF). Fourth Edition. A22-6884-3.
{{cite book}}: Unknown parameter|separator=ignored (help)CS1 maint: extra punctuation (link) - ^ IBM (February, 1972). IBM System/360 Model 67 Functional Characteristics (PDF). Third Edition. GA27-2719-2.
{{cite book}}: Check date values in:|date=(help); Unknown parameter|separator=ignored (help)CS1 maint: extra punctuation (link) - ^ IBM. IBM System/360 Model 75 Functional Characteristics (PDF). A22-6889-0.
{{cite book}}: Unknown parameter|separator=ignored (help)CS1 maint: extra punctuation (link) - ^ IBM (June, 1968). IBM System/360 Model 85 Functional Characteristics (PDF). Second Edition. A22-6916-1.
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External links
- Structural Aspects of the IBM System/360 model 85, Part II: The Cache
- IBM System/360 model 85 product announcement
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