IBM 2365 Processor Storage

The IBM 2365 Processor Storage is a magnetic-core memory storage unit that was a component of the IBM System/360 models 65,^[1] 67,^[2] 75^[3] and 85^[4] computers. Storage is implemented using magnetic cores with a storage width of 72 bits, which comprise 64 data bits (8 bytes, or one doubleword) plus 8 parity bits. The IBM 2365 model 1 contains 131,072 (128 K) bytes of memory; all other models contain 262,144 (256 K) bytes. The model 2 could be converted in the field to a model 13.

All models other than the model 1 consist of two memory stacks. Addressing for the stacks is interleaved, so the first 64-bit word is in one stack, the second in the other stack, and so forth. This improved performance when doing sequential access.

All models other than the model 5 have a cycle time of 750 nanoseconds.

Models

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.

Use with the System/360 model 85

The IBM 2365 model 5 was special because the System/360 model 85 accessed memory in 128-bit (16 byte) units, unlike the other System/360 models which supported the IBM 2365, all of which accessed 64-bit (8 byte) units. 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.

The IBM 2365 model 5 was used only with the System/360 model 85 with 524,288 (512 K) or 1,048,576 bytes (1 MB) of storage.

IBM 2385 Processor Storage

The IBM System/360 Model 85, when configured^[5] to have 2,097,152 (2 MB)^[6] or 4,194,304 (4 MB)^[7] bytes, used the IBM 2385 instead of the IBM 2365 Processor Storage, which had a cycle time of 960 nanoseconds^[8]

Other IBM products numbered 2385

2385 could also refer to:

• the processor of the iSeries 9406-170 (AS/400 family)^[9]
• IBM 33P2385 xSeries x336 Heatsink Copper^[10]
• IBM 53P2385 Internal QIC 60Gb SCSI-attached 5 1/4" (size) backup device^[11]

References

External links

• IBM System/360 model 85 product announcement