unused0

7 ms·

1.
by unused0 1y ago
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
2.
by unused0 3y ago
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 memory bus width was 72 bits, so it might have had an
3.
by unused0 3y ago
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 MIP.
4.
by unused0 3y ago
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 the collective decision not to include security
5.
by unused0 4y ago
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 above) was written in PL/I.
6.
by unused0 4y ago
Multics: Security.
7.
by unused0 4y ago
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 is started, the first instruction fetched; the address spac
8.
by unused0 4y ago
An FPGA implementation is underway. The X86 segmentation facility resembles Multics segments in name only.
9.
by unused0 4y ago
Run your own Multics: https://multics-wiki.swenson.org/index.php/Main_Page There are also several public access Multics systems up and running.
10.
by unused0 5y ago
The Burroughs system for the B5000 was written in Algol and preceded Multics.
11.
by unused0 5y ago
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 available, such as COBOL, FOTRAN, APL, BASIC, Assembler
12.
by unused0 6y ago
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 memory mapping and protection that that is the basis of Mul
13.
by unused0 6y ago
The website will be back online soon; the system can be accessed ssh dps8@m.trnsz.com
14.
by unused0 6y ago
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 address. The term "segment&quo
15.
by unused0 6y ago
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
16.
by unused0 7y ago
http://bitsavers.trailing-edge.com/pdf/honeywell/multics/AN5...
17.
by unused0 7y ago
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 Multics at: https://multicians.org&#
18.
by unused0 7y ago
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 afterwards), and code review practices. Reading the Multics B
19.
by unused0 7y ago
Getting multiple CPUs running has been quite an adventure.
20.
by unused0 7y ago
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 run-time bounds checking. On the other hand, there
21.
by unused0 7y ago
And two systems to the NSA.
22.
by unused0 7y ago
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 decompress packets into, and used ptrs to write to the buffer. (
23.
by unused0 7y ago
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 escalation.)
24.
by unused0 7y ago
The bulk of Multics is written in PL/I. See https://multicians.org/pl1.html for details.