The IBM System/370 Model 165 (and the Model 155) were jointly announced June 30, 1970 as "designed for ... the Seventies." That same day IBM announced the 370/195. They were the first three models of the

IBM System/370 The IBM System/370 (S/370) is a range of IBM mainframe computers announced as the successors to the IBM System/360, System/360 family on June 30, 1970. The series mostly maintains backward compatibility with the S/360, allowing an easy migrati ...

line of computers. Since none of them came with

virtual memory In computing, virtual memory, or virtual storage, is a memory management technique that provides an "idealized abstraction of the storage resources that are actually available on a given machine" which "creates the illusion to users of a ver ...

, "which was to be a hallmark of the 370 line", some said about these early members of the

family, especially about the 165 and 155, that they were not "the real 370 line." Three months later a fourth IBM System/370, the Model 145, was announced.

Virtual memory

The initially announced System/370 Models 165 and 155 systems did not support virtual memory. In 1972 an upgrade option was announced "to provide the hardware necessary to operate in a virtual memory mode." Unlike the IBM System/370 Model 145, which as early as June 1971 included the hardware necessary to support virtual memory, and for which a

microcode In processor design, microcode serves as an intermediary layer situated between the central processing unit (CPU) hardware and the programmer-visible instruction set architecture of a computer. It consists of a set of hardware-level instructions ...

update from a floppy disk, adding support for virtual memory, was announced in 1972, the Model 155 and Model 165 needed expensive hardware additions - $200,000 for the 155 and $400,000 for the 165 - to add virtual memory capability. An upgraded 165 was known as an IBM System/370 Model 165-II.

Emulation

The 370/165, when equipped with the appropriate compatibility feature, with the use of an

emulator In computing, an emulator is Computer hardware, hardware or software that enables one computer system (called the ''host'') to behave like another computer system (called the ''guest''). An emulator typically enables the host system to run sof ...

program permits running * 7070, 7072 and 7074 programs *

IBM 7080 The IBM 7080 was a variable word length BCD transistor computer in the IBM 700/7000 series commercial architecture line, introduced in August 1961, that provided an upgrade path from the vacuum-tube IBM 705 computer. The 7080 weighed about ...

programs *

709 __NOTOC__ Year 709 ( DCCIX) was a common year starting on Tuesday of the Julian calendar. The denomination 709 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe ...

, 7040, 7044, 7094 and 7094 II programs. The IBM 7070/7074 Compatibility Feature allowed the 165 to "run 7070 and 7074 programs at speeds that, in general, equal or exceed those of the original systems" and yet "not affect normal operation of System/370."

Physical memory

Although the joint 155/165 announcement did not have the word virtual, there were multiple references to (physical) memory, storage (both main memory and disk storage), and

cache memory In computing, a cache ( ) is a hardware or software component that stores data so that future requests for that data can be served faster; the data stored in a cache might be the result of an earlier computation or a copy of data stored elsew ...

under the name "buffer". The 155 had seven main memory choices, ranging from 256K to 2 MB; the 165: five possibilities, from 512K to 3 MB. Both models were described as having "a very high-performance buffer storage backed by a large" main memory.

Operating systems

The 370/165 supported both

DOS/360 Disk Operating System/360, also DOS/360, or simply DOS, is the discontinued first member of a sequence of operating systems for IBM System/360, System/370 and later mainframes. It was announced by IBM on the last day of 1964, and it was first d ...

and

OS/360 OS/360, officially known as IBM System/360 Operating System, is a discontinued batch processing operating system developed by IBM for their then-new System/360 mainframe computer, announced in 1964; it was influenced by the earlier IBSYS/IBJOB a ...

. Being members of the System/370 family, the Model 155 and Model 165 were compatible with each other. Lacking virtual memory support, neither machine, as announced, could run a virtual memory operating system. IBM provided and supported the free operating systems

DOS/VS Disk Operating System/360, also DOS/360, or simply DOS, is the discontinued first member of a sequence of operating systems for IBM System/360, System/370 and later mainframes. It was announced by IBM on the last day of 1964, and it was first del ...

(DOS/360 with virtual storage),

OS/VS1 Operating System/Virtual Storage 1, or OS/VS1, is a discontinued IBM mainframe computer operating system designed to be run on IBM System/370 hardware. It was the successor to the Multiprogramming with a Fixed number of Tasks (MFT) option of Sys ...

( OS/360 MFT with virtual storage), OS/VS2 Release 1 (

OS/360 MVT OS/360, officially known as IBM System/360 Operating System, is a discontinued batch processing operating system developed by IBM for their then-new System/360 mainframe computer, announced in 1964; it was influenced by the earlier IBSYS/IBJOB a ...

with virtual storage), termed SVS (Single Virtual Storage), and Release 2, termed

MVS Multiple Virtual Storage, more commonly called MVS, is the most commonly used operating system on the System/370, System/390 and IBM Z IBM mainframe computers. IBM developed MVS, along with OS/VS1 and SVS, as a successor to OS/360. It is unr ...

(Multiple Virtual Storage), and Virtual Machine Facility/370 (VM/370) on a 370/165 upgraded to a 370/165-II, exploiting the virtual memory hardware. IBM also provided

TSS/370 The IBM Time Sharing System TSS/360 is a discontinued early time-sharing operating system designed exclusively for a special model of the System/360 line of mainframes, the Model 67. Made available on a trial basis to a limited set of customer ...

for the 165-II as a PRPQ, while others ported 3rd party operating systems, e.g.,

Michigan Terminal System The Michigan Terminal System (MTS) is one of the first time-sharing computer operating systems.. Created in 1967 at the University of Michigan for use on IBM System/360, IBM S/360-67, S/370 and compatible mainframe computers, it was developed and ...

(MTS),

Orvyl ORVYL is a time-sharing monitor developed by Stanford University for IBM System/360 and System/370 computers in 1967–68.360/67 The IBM System/360 Model 67 (S/360-67) was an important IBM mainframe model in the late 1960s. * It had "its own powerful operating system... heTime Sharing System monitor (TSS)" offering "virtually instantaneous access to and response from t ...

S/370 The IBM System/370 (S/370) is a range of IBM mainframe computers announced as the successors to the System/360 family on June 30, 1970. The series mostly maintains backward compatibility with the S/360, allowing an easy migration path for cust ...

s with virtual memory hardware.

Notes

References