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Multics ran on Honeywell 6180 and DPS8/M machines. They had 36 bit words like the PDP-10. They also had instructions that would operate o in 6 or 9 bit characters in the word

The VAX had byte addressable memory, the DPS8/M word 36 bit word addressable, so I suspect that byte oriented instructions might have an edge on the VAX. Contrawise, the DPS8/M mem…

According to wikipedia, the 6000s ran about 1 MIP and the DPS8/Ms topped out about 1.7 MIPS. Talking with people that worked on Multics, they generally say the 6000s were about 1 M…

Multics achieved security by building it into the h/w. That caused the h/w to be more expensive and slower. The system market these days is all about price/performance ratio and th…

IIRC,Primos was written in FORTRAN (with language extensions including the ability to pass a statement number as a parameter, allowing longjmp() like behavior). Multics (as noted a…

Multics: Security.

Non-single level stores are copy-on-demand. Typically, a process runs a program by starting with an empty address space and mapping the executable code into that space. The program…

An FPGA implementation is underway. The X86 segmentation facility resembles Multics segments in name only.

Run your own Multics: https://multics-wiki.swenson.org/index.php/Main_Page There are also several public access Multics systems up and running.

The Burroughs system for the B5000 was written in Algol and preceded Multics.

Multics is written almost entirely in PL/I, plus some assembly for bootup, some messy low level stuff, and time critical bits like process switching. Many additional languages are …

Multics was co-developed with the hardware; that hardware contains Multics specific features that are needed to implement Multics. Segment tables, Rings, Gates and more. enable the…

The website will be back online soon; the system can be accessed ssh dps8@m.trnsz.com

https://multicians.org/mgs.html#segment segment User-visible subdivision of a process's address space, mapped onto a storage system file. Each segment is 1MB long, and has a zero a…

But oddly, in Multics they became "ec" (execute command maybe?). r 13:41 0.055 7 ls >sc1>system_start_up.ec Segments = 1, Lengths = 2. r w 2 system_start_up.ec

http://bitsavers.trailing-edge.com/pdf/honeywell/multics/AN5...

Porting is unfeasible; Multics relies on hardware features not available. An emulator for the original hardware can be found at: http://ringzero.wikidot.com/ Information about Mult…

I would argue that Multics security was due more to the ring and gate hardware architecture, that security was designed into the software from day 0 (rather then being grafted in a…

Getting multiple CPUs running has been quite an adventure.

PL/I doesn't prevent memory access bugs, but it makes it easier to do good programming. For example, parameters are passed by descriptor, so the allocated size is passed allowing r…

And two systems to the NSA.

A writeup is on my round tuit list; some day soon. PL/I does bounds checking on arrays, but not on pointers. The Kermit server allocated an insufficiently large buffer to decompres…

Sadly, a buffer overflow attack has been found; it is possible to write bad PL/I. (The defective code is a user-space tool, so at best, a remote code exploit. No privilege escalati…

The bulk of Multics is written in PL/I. See https://multicians.org/pl1.html for details.