Date: Tue, 11 Dec 2001 09:00:20 -0800 From: "Brian D. Moffet" <brianm@moffetimages.com> To: Bakul Shah <bakul@bitblocks.com> Cc: freebsd-hardware@freebsd.org Subject: Re: i286 Message-ID: <5.1.0.14.2.20011211085224.00ae07b8@orac.moffetimages.com> In-Reply-To: <200112110552.AAA08679@valiant.cnchost.com> References: <Your message of "Mon, 10 Dec 2001 15:02:26 MST." <15381.12530.404008.733531@caddis.yogotech.com>
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At 09:52 PM 12/10/2001 -0800, you wrote: >Not that anyone cares any more but... i286 provides good >enough protection -- you can have each prcoess in its own >protected address space without any external h/w support >(like we had to do for Moto 68000 based machines). What it >didn't provide was support for paging. A company called >Microport released a "real" unix for 286 in, I think, 1985. >Another company called Bell Technologies used to sell PC/ATs >bundled with Microport's Unix and their own drivers for >various I/O devices until Intel bought them out. Microport >is still around but don't know if they sell Unix on PC/ATs >anymore! SCO, at that time "Santa Cruz Operation" also provided a "real" Unix, ie Xenix. Supported paging only on the level of 64K segments. There were some rather interesting problems with it. There was a constant battle between Microport and SCO because of some technology that they used, which was claimed by SCO to be proprietary. The ability to change console screens (multiscreens they were called) was one of those. That came from SCO. Of course Xenix originally came from Microsoft in the early 80's, so it all boils down to that large company in the beginning ;-) The 286 version worked better than the 8086 version though. That was able to support memory management by taking advantage of the fact that it was a 16 nit machine, and used the segment register to act as a very crude memory management. There was no protection as you might guess. I remember we had what was called a "JAM" area, where the relocation information for libraries would be held. When a process started, the kernel would write the correct offsets (since the process had to know about the actual address) into this area, and then start the process running. I remember working on these two while I worked at SCO, I was in the tech support department. I eventually moved to kernel engineering to work on the 386 port of Unix. Too much trivia for you :-) Brian Brian D. Moffet brianm@moffetimages.com -- http://www.moffetimages.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hardware" in the body of the message
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