Path: utzoo!attcan!uunet!tank!ncar!asuvax!cs.utexas.edu!usc!snorkelwacker!spdcc!esegue!johnl
From: johnl@esegue.segue.boston.ma.us (John R. Levine)
Newsgroups: comp.sys.ibm.pc
Subject: Re: 386 instructions
Message-ID: <1990Jan12.063959.7731@esegue.segue.boston.ma.us>
Date: 12 Jan 90 06:39:59 GMT
References: <13346@garnet.BBN.COM> <580@watserv1.waterloo.edu> <6142@internal.Apple.COM> <8166@portia.Stanford.EDU>
Reply-To: johnl@esegue.segue.boston.ma.us (John R. Levine)
Distribution: comp
Organization: Segue Software, Cambridge MA
Lines: 13

In article <8166@portia.Stanford.EDU> dhinds@portia.Stanford.EDU (David Hinds) writes:
>    On a tangent to the previous articles in the series, why are these DOS
>extenders and things needed anyway??? ... Any DOS program can simply use
>32-bit addresses to access extended memory.

In 386 real mode, you can use all of the 32 bit registers but for some reason
you can only use 20 bit addresses.  Also, in real mode it needs to generate
operand and address size override bytes so the code is a lot larger than it
would be in protected mode.
-- 
John R. Levine, Segue Software, POB 349, Cambridge MA 02238, +1 617 864 9650
johnl@esegue.segue.boston.ma.us, {ima|lotus|spdcc}!esegue!johnl
"Now, we are all jelly doughnuts."