IBM 2365 Processor Storage
| Company type | Computer memory hardware |
|---|---|
| Industry | Computer hardware |
| Founded | 1965 |
| Headquarters | United States |
| Products | Magnetic-core memory devices for IBM System/360 models 65, 67, 75, and 85 |
The IBM 2365 Processor Storage is a magnetic-core memory device utilized in several IBM System/360 models, specifically the 65, 67, 75, and 85, which were introduced between 1965 and 1968.
This storage unit employs magnetic cores arranged in 72-bit widths—comprising 64 bits for data (equivalent to 8 bytes or one doubleword) plus an additional 8 bits for parity checking. The model 1 of the IBM 2365 offers a capacity of 131,072 (128 K) bytes, while other variants provide 262,144 (256 K) bytes. Notably, the model 2 can be field-upgraded to function as a model 13.
With the exception of model 1, all versions incorporate two memory stacks that utilize interleaved addressing. This design alternates 64-bit words between the stacks to improve performance during sequential data access.
All models run at a cycle time of 750 nanoseconds, except for model 5.
Models
The IBM 2365 family includes models tailored for distinct System/360 configurations:
- Model 1: Designed for the System/360 model 65 (single processor)
- Model 2: Compatible with System/360 models 65 (single processor) and 67-1
- Model 3: Intended for the System/360 model 75
- Model 5: Used with the System/360 model 85
- Model 12: For the System/360 model 67-2
- Model 13: Suited to the multiprocessor version of the System/360 model 65
Use with the System/360 model 85
The IBM 2365 model 5 is unique in supporting the System/360 model 85’s distinctive 128-bit (16-byte) memory access, differing from other models that operate on 64-bit units. It functions with a cycle time of 1040 nanoseconds and requires either two or four units. Since the CPU operates faster than the memory, two units are configured with two-way interleaving, while four units employ four-way interleaving. Internally arranged as two-way interleaved, this configuration allows sequential memory operations to efficiently cycle through all components.
This model is exclusively available for System/360 model 85 systems equipped with either 524,288 (512 K) or 1,048,576 bytes (1 MB) of memory.
IBM 2385 Processor Storage
For configurations of the IBM System/360 Model 85 featuring larger capacities—2,097,152 bytes (2 MB, designated as 360/85 K85) or 4,194,304 bytes (4 MB, known as 360/85 L85)—the IBM 2385 Processor Storage replaces the IBM 2365. The IBM 2385 offers an improved cycle time of 960 nanoseconds compared to the IBM 2365 model 5’s cycle time of 1,040 nanoseconds.