Path: utzoo!yunexus!geac!syntron!jtsv16!uunet!husc6!think!ames!ncar!tank!uxc!uxc.cso.uiuc.edu!uxg.cso.uiuc.edu!uxe.cso.uiuc.edu!mcdonald
From: mcdonald@uxe.cso.uiuc.edu
Newsgroups: comp.sys.ibm.pc
Subject: 386 run time testing
Message-ID: <45900168@uxe.cso.uiuc.edu>
Date: 16 Oct 88 17:05:00 GMT
Article-I.D.: uxe.45900168
Lines: 14
Nf-ID: #N:uxe.cso.uiuc.edu:45900168:000:643
Nf-From: uxe.cso.uiuc.edu!mcdonald    Oct 16 12:05:00 1988



Does anyone out there know a reliable, safe (hopefully not generating
traps) method of having a running program (Microsoft C 5.1) 
determine whether it is running on an 80386 (as opposed to an 8086 or
80286)? I discovered that by coding one 11 line subroutine from my
TeX screen previewer in assembler, using real 32 bit moves and
shifts, that I can get a 35% speed improvement. (I made my non-386
assembler do this by sticking in 
     db  066h
opcode prefixes explicitly.) I would like to put this change in my
distributed version, with a run time test to distinguish it from
the 8086/80286 version in C. 
Doug McDonald (mcdonald@uiucuxe)