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Path: utzoo!watmath!clyde!bonnie!akgua!gatech!seismo!lll-crg!well!farren
From: farren@well.UUCP (Mike Farren)
Newsgroups: net.micro,net.arch
Subject: Re: Re: 386 Family Products (8086 sucks
Message-ID: <351@well.UUCP>
Date: Tue, 17-Dec-85 06:19:16 EST
Article-I.D.: well.351
Posted: Tue Dec 17 06:19:16 1985
Date-Received: Fri, 20-Dec-85 00:44:09 EST
References: <133@daisy.UUCP> <97800013@ima.UUCP> <464@looking.UUCP> <154@ism780c.UUCP>
Organization: Whole Earth Lectronic Link, Sausalito, CA
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Xref: watmath net.micro:13149 net.arch:2321

In article <154@ism780c.UUCP>, tim@ism780c.UUCP (Tim Smith) writes:
> It could have been done with no work from the compiler if Intel had
> put the bits in a reasonable place.  A full pointer has a selector and
> an offset.  Here is what they look like:
> 
>     Selector:
>     --------------------------------------------------------
>     | Segment Number ( 13 bits )  | Other Stuff ( 3 bits ) |
>     --------------------------------------------------------
> 
>     Offset:
>     --------------------------------------------------------
>     |             Offset in Segment ( 16 bits )            |
>     --------------------------------------------------------
> 

	Huh?  Wha?  Am I awake yet?   That is NOT the way the segments work;
the "Other Stuff" is not a pointer into any kind of table, in fact, it doesn't
exist at all.  A full pointer on the 8086 is two words. The first word is
nothing more than a pointer to a 16-byte boundary which is the beginning of
the 64K segment.  The second word is the offset within the segment, and is
simply added to the (left-shifted 4 bits) first word to obtain a 20-bit real
address.

-- 
           Mike Farren
           uucp: {dual, hplabs}!well!farren
           Fido: Sci-Fido, Fidonode 125/84, (415)655-0667
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