Re: Memory above 640K being redundant (or something like that)

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#8590

From: Jerry Sheckel
Date: Wed, 27 Mar 1991 16:32

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ralf+@cs.cmu.edu (Ralf Brown) writes:
>
>>Ok, so WHAT address does a 286/386/486 jump to when it resets, (or at
>>boot time)??
>
>286 = FFFFFF:0
>386/486 = FFFFFFFF:0
>
>In other words, the start of the highest segment in the address space.
>

What!?  I always thought that both the 286 and the 386/486 are in real mode
when they reset, so they still jump to FFFF:0.  Am I wrong?  How can the
286 (or 386/486) jump to an address above 1MB if the protected mode selectors
for the segment registers haven't been created yet?  If the 386/486 supports
4GB segments, what does "highest segment in the address space" mean?

>
>{backbone}!cs.cmu.edu!ralf  ARPA: RALF@CS.CMU.EDU   FIDO: Ralf Brown 1:129/3.1
>
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Path: arc1-ca.pugleaf.net!utzoo!utgpu!news-server.csri.toronto.edu!rpi!bu.edu!polygen!jerry
From: jerry@polygen.uucp (Jerry Sheckel)
Newsgroups: comp.sys.ibm.pc.misc,comp.sys.ibm.pc.hardware,comp.os.msdos.programmer
Subject: Re: Memory above 640K being redundant (or something like that)
Message-ID: <1019@stewart.UUCP>
Date: 27 Mar 91 16:32:15 GMT
Reply-To: jerry@stewart.UUCP (Jerry Shekhel)
Organization: Polygen Corporation, Waltham, MA
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