Messages in this thread |  | | From | Marty Fouts <> | Subject | RE: SCO: "thread creation is about a thousand times faster than o n | Date | Mon, 28 Aug 2000 20:34:41 -0700 |
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For PDP-11 trivia, see
http://www.telnet.hu/hamster/pdp-11/1120.html
where the question of MMU is answered thusly:
Interesting options: MX11 - Memory Extension Option: this enabled the usage of 128 KW memory (18-bit addressing range); KS11: this option provided hardware memory protection, which the plain /20 lacked. Both options were developed by the Digital CSS (Computer Special Systems).
-----Original Message----- From: yodaiken@fsmlabs.com [mailto:yodaiken@fsmlabs.com] Sent: Monday, August 28, 2000 4:14 PM To: Alexander Viro Cc: yodaiken@fsmlabs.com; Albert D. Cahalan; linux-kernel@vger.kernel.org Subject: Re: SCO: "thread creation is about a thousand times faster than on
On Mon, Aug 28, 2000 at 07:16:34PM -0400, Alexander Viro wrote: > > > Funny. I didn't know that -11/20 had memory protection... > > > > PDP-11 had good memory protection. I think PDP 8 may even have had it. > > None of this newfangled paging b.s. though. > > I think you are mixing -11/20 with -11/45... (-8 is completely irrelevant > and I don't know whether there was any memory protection on -{7,9}, but I > really doubt it).
I think the 11/20 had an optional MMU, but I'm not sure. I have a vague memory that the 8 had a map register, but that may be totally wrong.
UNIX as a useful OS begins with V6 which ran on the 11/40 and up and these, for sure, had segments. Even V5 needed an 11/40. See sheets 16 & 17 in the Lions book.
But I'd love to see a reasonable argument as to why fork/exec would be useful on an mmu-less processor in the current state of the field. 90% of the semantics disappear.
-- --------------------------------------------------------- Victor Yodaiken Finite State Machine Labs: The RTLinux Company. www.fsmlabs.com www.rtlinux.com
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