IBM System/360 architecture: Difference between revisions

Revision as of 15:45, 15 February 2022

Revision as of 15:50, 15 February 2022

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* 24-bit (16 MB) byte-addressable memory space

* [[Big-endian]] byte/word order

* A ''standard instruction set'', including fixed-point binary arithmetic and logical instructions, present on all System/360 models (except the model[[IBM System/360 Model 20|Model 20]], see below).

** A ''commercial instruction set'', adding decimal arithmetic instructions, is optional on some models, as is a ''scientific instruction set'', which adds floating-point instructions. The ''universal instruction set'' includes all of the above plus the storage protection instructions and is standard for some models.

** The [[IBM System/360 Model 44|Model 44]] provides a few unique instructions for data acquisition and real-time processing and is missing the storage-to-storage instructions. However, IBM offered a '''Commercial Instruction Set"'' feature that ran in bump storage and simulated the missing instructions.

** The [[IBM System/360 Model 20|Model 20]] offers a stripped-down version of the standard instruction set, limited to eight general registers with halfword (16-bit) instructions only, plus the commercial instruction set, and unique instructions for input/output.

** The [[IBM System/360 Model 67|Model 67]] includes some instructions to handle 32-bit addresses and "dynamic address translation", with additional privileged instructions to provide virtual memory.<ref>{{cite book|last1=IBM Corporation|title=IBM System/360 System Summary|date=1974|page=3-3|url=http://bitsavers.org/pdf/ibm/360/systemSummary/GA22-6810-12_360sysSumJan74.pdf|access-date=July 16, 2017}}</ref>