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From: resnicks@netcom.COM (Steve Resnick)
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: <1991Mar29.000845.8125@netcom.COM>
Date: 29 Mar 91 00:08:45 GMT
References: <1019@stewart.UUCP>
Organization: Netcom - Online Communication Services  UNIX System {408 241-9760 guest}
Lines: 32

In article <1019@stewart.UUCP> jerry@stewart.UUCP (Jerry Shekhel) writes:
>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?

That information seems to jibe with teh intel documentation. 


- Steve

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