IBM System/360 Model 65
| Industry | Computer hardware |
|---|---|
| Predecessor | IBM System/360 Model 60, IBM System/360 Model 62 |
| Founded | April 1965 |
| Defunct | March 1974 |
| Products | Mainframe computer |
The IBM System/360 Model 65 belongs to the IBM System/360 series and was introduced in April 1965. It succeeded the Model 60 and Model 62, which were announced earlier but never reached the market. Production of the Model 65 ceased in March 1974.
Models
Within the S/360-65 lineup, there are six distinct submodels primarily differentiated by the amount of core memory installed. The G65, H65, I65, IH65, and J65 configurations feature 128K, 256K, 512K, 768K, and 1MB of core memory respectively. By 1974, the smallest G variant was phased out. A multiprocessor (MP) version was also made available, supporting system memory ranging from 512K up to 2MB. Moreover, the system can be expanded with IBM 2361 Large Capacity Storage units, offering up to 8MB of slower auxiliary memory compared to the main processor storage.
Relative performance
The Model 65 provides performance exceeding three times that of an S/360-50. In contrast, the subsequent higher model, the Model 75, delivers less than twice the processing speed of the S/360-65.
Features
This model fully implements the System/360 "universal instruction set" architecture, incorporating standard floating-point, decimal, and character operation capabilities. Optional compatibility features allow it to emulate earlier IBM computer systems such as the 7040/7044, 7090/7094, 7070/7074, and IBM 7080.
Its main memory supports interleaving techniques to enhance access speed.
Similar to the Model 67, the Model 65 was available in a dual-processor configuration. These multiprocessing variants utilize two I65s, IH65s, or J65s sharing common main memory accessible by both CPUs.
Systems software
The Model 65 is compatible with IBM Basic Programming Support (BPS), DOS/360, TOS/360, as well as multiple OS/360 versions including PCP, MFT, and MVT. Among these, MVT was frequently selected as the operating system for this model.
For dual-CPU setups, a specialized MVT variant named MP65 is required; it leverages CPU-to-CPU communication instructions such as Write Direct. The Model 65MP supports asymmetric multiprocessing where certain input/output devices are dedicated to a single processor.
Time-sharing functionality is facilitated through IBM's Time Sharing Option (TSO) available on this model.
See also
- Smithsonian Institution – possesses a System/360 Model 65 unit; however, it is currently not exhibited publicly