Path: utzoo!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!mcsun!sunic!nuug!sigyn.idt.unit.no!torb
From: torb@idt.unit.no (Tor Brekke)
Newsgroups: alt.msdos.programmer
Subject: Re: 386 instructions
Message-ID: <1990Jan18.105441.15784@idt.unit.no>
Date: 18 Jan 90 10:54:41 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> <1452@gould.doc.ic.ac.uk>
Reply-To: torb@garm.UUCP (Tor Brekke)
Organization: Div. of CS & Telematics, Norwegian Institute of Technology
Lines: 18

In article <1452@gould.doc.ic.ac.uk> zmact61@doc.ic.ac.uk (D Spinellis) writes:
>In article <1990Jan17.102756.8171@idt.unit.no> torb@grimne.UUCP (Tor Brekke) writes:
>>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 never seen it it documented, but one might get a hint that it
is possible in section 14.5 of "80386 Programmer's Reference Manual"
where switching to real-address mode is described. It says that
all segment registers must be loaded with a descriptor to a segment of
size 64KB *before* entering real mode. This is bound to make people
try other sizes :-)

Tor Brekke
Email: torb@idt.unit.no