> they did not have to worry about backwards compatibility, so they could do fancy stuff like virtual memory IBM did have to worry about backwards compatibilit

> they did not have to worry about backwards compatibility, so they could do fancy stuff like virtual memory IBM did have to worry about backwards compatibility, but they delivered a virtual memory machine, the System/360 Model 67, by 1966.[1] The System/370, on which virtual memory was standard, was delivered starting in 1971.[2] Their VM/370 operating system (1972) was a hypervisor (IBM coined the term back then) that provided virtual System/370 machines.[3] You could actually run instances of VM/370 in VM/370 virtual machines. It amazes me that this technology was already being used a half-century ago. [1] https://en.wikipedia.org/wiki/IBM_System/360_Model_67 https://en.wikipedia.org/wiki/IBM_System/360_Model_67 [2] https://en.wikipedia.org/wiki/IBM_System/370 https://en.wikipedia.org/wiki/IBM_System/370 [3] https://en.wikipedia.org/wiki/VM_(operating_system) https://en.wikipedia.org/wiki/VM_(operating_system)