3 May
2016
3 May
'16
11:15 a.m.
On May 3, 2016, at 1:55 PM, Erik Baigar <erik at
baigar.de> wrote:
On Tue, 3 May 2016, Paul Koning wrote:
Keep in mind that mapping and protection are not required to build a multi-user system.
DEC did timesharing on the PDP-11/20 (RSTS-11) and on the PDP-8 without either. And
multiprogramming goes back much further, at least as far as the THE operating system in
1964, on the EL-X8. That OS is particularly interesting because it has virtual memory and
demand paging without any hardware help, without address mapping or protection.
In all these cases, you need help from the compilers to keep things safe. Burroughs
mainframes do the same sort of thing, though that's not so obvious: the OS security is
dependent on the fact that ordinary users can't write and execute ESPOL programs.
paul
No, the PDP-11 offered this starting with the 11/45, in 1971.
OK, that is a hint - the 11/45 also had a MMU and obviosly must
have been a great machine for multi-user stuff.