Article 329 of alt.msdos.programmer: | |
Path: | icdoc!tsun6.doc.ic.ac.uk!zmact61 |
>From: | zmact61@tsun6.doc.ic.ac.uk.doc.ic.ac.uk (D Spinellis) |
Newsgroups: | alt.msdos.programmer |
Subject: | Re: 386 instructions |
Message-ID: | <1452@gould.doc.ic.ac.uk> |
Date: | 17 Jan 90 17:21:18 GMT |
References: | <13346@garnet.BBN.COM> <580@watserv1.waterloo.edu> <6142@internal.Apple.COM> <8166@portia.Stanford.EDU> <1451@gould.doc.ic.ac.uk> <1990Jan17.102756.8171@idt.unit.no> |
Sender: | news@doc.ic.ac.uk |
Reply-To: | zmact61@doc.ic.ac.uk (D Spinellis) |
Organization: | Imperial College Department of Computing |
Lines: | 24 |
Content-Length: | 1238 |
In article <1990Jan17.102756.8171@idt.unit.no> torb@grimne.UUCP (Tor Brekke) writes:
>In article <1451@gould.doc.ic.ac.uk> dds@cc.ic.ac.uk (Diomidis Spinellis) writes:
>>Sorry, but the above is not exactly correct. It is true that most of the
>>386 instructions can be used in the real mode, but the segment limit is
>>still limited to 64K.
>
>Sorry, byt this is not correct either. It is possible to trick the 386
>into beliving that it's segments are larger than 64K in real mode.
[...]
>If a descriptor i set up
>with a limit larger than 64K and left in one of the segment registers
>when reentering real mode, the processor will still believe that the
>segment has the old size.
Is this a bug of the 386 or a documented feature? I have not found any mention
of it in the Intel literature. It sounds very useful, but if it is
undocumented it might go away in new chip releases.
Diomidis
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