3 May
2016
3 May
'16
9:17 a.m.
On May 3, 2016, at 11:52 AM, Erik Baigar <erik at
baigar.de> wrote:
Dear Experts,
during discussing the Rolms I came accross the following question:
What was the first (Minicomputer) architecture which offered
memory- and IO protection? I'd define the minimum requirements as:
- Existence of a superuser mode (Rolm calls this Executive mode)
- Existence of a user mode (With at least two users, Rolm offers 4)
- In superuser mode, IO and memory protection for each user can be
set up individually.
- Any access violation is trapped and handeled by superuser code.
- Of course commands for mode switching and setting up the
memory and IO ranges must exist.
...
Probably OS/2 in 1987 was one of the first home computer OSes to
support memory protection (how about IO protection?), BSD on some
Digital PDP-* was earlier (1977?) but still after the 1602.
No, the PDP-11 offered this starting with the 11/45, in 1971.
In larger computers the feature is much older. Consider the CDC 6600 (1964). While not
all the properties you mentioned apply because I/O is in separate peripheral processors,
the notion of a privileged mode and address mapping is there. And even that isn't the
oldest example, I think.
paul