The Atlas Supervisor for the Atlas
MCP for the Burroughs B5000
MTS, TSS/360 and CP/CMS for the IBM System/360 Model 67
Multics for the GE 645
the Time Sharing Operating Process for the RCA Spectra 70/46
Virtual memory is an integral part of a contemporary computer architecture; implementations require hardware support, usually in the kind of a memory management unit built in to the CPU. While not necessary, emulators and virtual machines can employ hardware support to increase performance of their virtual memory implementations.[1] Consequently, older operating systems, such as those for the mainframes of the 1960s, and those for personal computers of the early to mid-1980s (e.g. DOS),[2] usually have no virtual memory functionality,[dubious � discuss] though notable exceptions for mainframes of the 1960s include:
The Apple Lisa is an example of a personal computer of the 1980s that features virtual memory.
Most modern operating systems that support virtual memory also run each method in its own dedicated address space. Each program thus appears to have sole access to the virtual memory. However, some older operating systems (such as OS/VS1 and OS/VS2 SVS) and even modern ones (such as IBM i) are single address space operating systems that run all processes in a single address space composed of virtualized memory.
Embedded systems and other special-purpose computer systems that require speedy and/or consistent response times may opt not to make use of virtual memory due to decreased determinism; virtual memory systems trigger unpredictable traps that may produce undesirable "jitter" in the coursework of I/O operations. This is because embedded hardware costs are often kept low by implementing all such operations with application (a method called bit-banging) than with dedicated hardware.
MCP for the Burroughs B5000
MTS, TSS/360 and CP/CMS for the IBM System/360 Model 67
Multics for the GE 645
the Time Sharing Operating Process for the RCA Spectra 70/46
Virtual memory is an integral part of a contemporary computer architecture; implementations require hardware support, usually in the kind of a memory management unit built in to the CPU. While not necessary, emulators and virtual machines can employ hardware support to increase performance of their virtual memory implementations.[1] Consequently, older operating systems, such as those for the mainframes of the 1960s, and those for personal computers of the early to mid-1980s (e.g. DOS),[2] usually have no virtual memory functionality,[dubious � discuss] though notable exceptions for mainframes of the 1960s include:
The Apple Lisa is an example of a personal computer of the 1980s that features virtual memory.
Most modern operating systems that support virtual memory also run each method in its own dedicated address space. Each program thus appears to have sole access to the virtual memory. However, some older operating systems (such as OS/VS1 and OS/VS2 SVS) and even modern ones (such as IBM i) are single address space operating systems that run all processes in a single address space composed of virtualized memory.
Embedded systems and other special-purpose computer systems that require speedy and/or consistent response times may opt not to make use of virtual memory due to decreased determinism; virtual memory systems trigger unpredictable traps that may produce undesirable "jitter" in the coursework of I/O operations. This is because embedded hardware costs are often kept low by implementing all such operations with application (a method called bit-banging) than with dedicated hardware.
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