Tedious and uninformative
This article spends 3 1/2 pages of a 4 page article on computer technologies through the mid-1990s, and then fails to show how the lessons of memory protection (and privileged instructions as well) are insufficient for modern computer architecture.
This was a complete and utter waste of my time.
For what it's worth, my synopsis of why memory protection and privileged instructions are insufficient for modern computer architectures can be outlined as follows:
(1) Modern OSes (Windows, OSx, Linux, presumeably IOs too) do run with protected memory, privileged instructions, etc.
(2) Computers are among the most hideously complex devices created. (And networked systems of computers are even worse.)
(3) The complication of (2) above means that the OSes on those devices will need updates (necessarily from external sources.) Networks, USB drives, etc. make this convenient and possible.
(4) Most computers sold to end-users as such (or as phones, game devices, tablets, etc. other infotainment) are incomplete - they do NOT have what the end user wants, so a mechanism must be given to obtain that from external sources.
(6) Various extensions to the underlying OS in order to provide better speed (i.e.: kernel level device drivers, extensible file systems, etc.) or to patch flaws in the OS security model (i.e.: anti-virus hooks) complicate the security model, weakening it overall.
(7) Software installation often requires higher privileges in order to install software the customer wants. This is as often for the convenience of the software developer as it is required by the underlying security model.
(8) Software manufacturers / publishers have evolved a model whereby they're not necessarily liable for flaws in their software. This leaves the need to publish quickly paramount in their priorities.