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From: tim@ism780c.UUCP (Tim Smith)
Newsgroups: comp.sys.m68k,comp.sys.intel
Subject: Re: Re: Re: Recent Motorola ad seen in Byte
Message-ID: <6020@ism780c.UUCP>
Date: Tue, 21-Apr-87 16:47:40 EST
Article-I.D.: ism780c.6020
Posted: Tue Apr 21 16:47:40 1987
Date-Received: Thu, 23-Apr-87 04:41:32 EST
References: <930@intsc.UUCP> <1517@ncr-sd.SanDiego.NCR.COM> <932@intsc.UUCP>
Reply-To: tim@ism780c.UUCP (Tim Smith)
Distribution: comp
Organization: Interactive Systems Corp., Santa Monica CA
Lines: 24
Xref: mnetor comp.sys.m68k:383 comp.sys.intel:175

In article <932@intsc.UUCP> tomk@intsc.UUCP (Tom Kohrs @fae) writes:
<
< doing bank selections or overlays.  The 286 architecture is considerably
< nicer than what was the dominate 16bit mini at the time, the PDP-11.  In
< 1980 the idea that you could get the cpu power of an 11/70 on a chip with
< a cleaner memory management model got a lot of people excited.  

So how come you guys put the index in the upper 13 bits of a selector and
the GDT/LDT bit and the priveledge bits in the low 3 bits?  If you had put
the index in the low 13 bits, then the LDT/GDT bit, and then the rest,
one could have gotten a 29 bit linear address space by setting up
non-overlapping 64k segments.

This would have eliminated the major complaint that people who program
in higher level languages have against the 286.

The only reason I can think of is that it saves having to shift the
index to get the offset into the GDT/LDT, but my friends who design
CPUs and do VLSI, and all that rot, tell me that this is no problem.
-- 
Tim Smith			"Hojotoho! Hojotoho!
uucp: sdcrdcf!ism780c!tim	 Heiaha! Heiaha!
Delph or GEnie: Mnementh	 Hojotoho! Heiaha!"
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