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Path: utzoo!linus!philabs!micomvax!othervax!ray
From: ray@othervax.UUCP (Raymond D. Dunn)
Newsgroups: net.micro
Subject: Re: 386 Family Products
Message-ID: <738@othervax.UUCP>
Date: Mon, 9-Dec-85 11:14:49 EST
Article-I.D.: othervax.738
Posted: Mon Dec  9 11:14:49 1985
Date-Received: Wed, 11-Dec-85 10:12:17 EST
References: <129@intelca> <4400130@uiucdcsb> <6185@utzoo.UUCP> <433@ecn-pc.UUCP> <434@ecn-pc.UUCP>
Reply-To: ray@othervax.UUCP (Raymond D. Dunn)
Organization: Philips Information Systems - St. Laurent  P.Q., Canada
Lines: 37
Summary: 

>>1) Last I checked, the 386 had segments just a bit larger than 64k.
                                          ^^^^^^^^^^^^^^^^^
>     True, INTEL finally fixed (badly) one of their major flaws.
                                ^^^^^^^

Hey folks, there's enough to argue about without getting *facts* wrong!
Sure there are things wrong with the 386, but this is not one of them.

As has been said on this group before, in protected mode, the maximum
segment size on the 386 is the *same* as the maximum physical memory
size: 2^32, or 4 Gigabytes.

This means that software can, if required, set all segments registers
to address all of memory, and thus run 100% as if segmentation did
not exist.

It also means that, in addition to the features provided by the MMU,
software can *IF REQUIRED*, use the segmentation capabilities for its
own requirements with *NO DISADVANTAGES*.  This includes stack
boundary checking, fast swapping/boundary checking of data contexts
etc.

These are facilities which are available *within each task*.

They are not just restricted to the protection etc provided by an MMU
under the control of the operating system to protect one task from
another.

Lets get it clear:

The 386 segmentation registers give *additional* functionality over
say, the 680x0.

The 386 segmentation registers do *not* decrease functionality or
ease of use, as they did on the 8086.

Ray Dunn.  ..philabs!micomvax!othervax!ray