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From: dave@tygra.UUCP (David Conrad)
Newsgroups: comp.lang.pascal,comp.sys.ibm.pc.hardware
Subject: Re: 8086 vs. 80286 : How to detect which one?
Message-ID: <1991Mar28.094957.11834@tygra.UUCP>
Date: 28 Mar 91 09:49:57 GMT
References: <1991Mar26.223512.1@rulcri.leidenuniv.nl>
Organization: CAT-TALK Conferencing System, Detroit, MI
Lines: 50

In article <1991Mar26.223512.1@rulcri.leidenuniv.nl> vereijken@rulcri.leidenuniv.nl (Jan Joris Vereijken) writes:
>Hi,
>
>
>Actually, I want more, I want a way where I can decide wheter I'm dealing with:
>
>8088 / 8086 / 80188 / 80186 / V20 / V30 / 80286 / 80386 / 80486

The only one I know how to do is 86,186,286 vs. 386,486 (the i586 is due out
this year!).  The 386 only looks at the low 5 bits of CL when shifting (hey,
the registers are only 32 bits wide, why would you need to shift farther
than that!)  The earlier processors are not so smart.  They do what you tell
them, even if it makes no sense (the way computers *should* work! :).
 
     mov ax, 1
     mov cl, 33 ; or 21, if .RADIX 16 (hex)
     shl ax, cl ; don't use extended shl instruction, may be on 8086/88
     jnz atleast386
atmost286:
     ...
atleast386:
     ...
 
On 286's and previous all the bits would be shifted right out of AX, but on
the 386, 486, and (presumably) 586 shl ax, 33 is equivalent to shl ax, 1, so
AX ends up with 2 in it.  I don't know if the equivalent TPas would work:
 
     If (1 SHL 33) = 2 then
       (* 386+ *)
     else
       (* 286- *);
 
If some kind soul with a 386 would run the following test program, I'd be
grateful:
 
begin
  writeln (1 SHL 33);
end.
 
Damn!  It produces 2 on my 286!?!  Either TP is too smart, or my information
is wrong.  I got the info from a magazine, Dr. Dobbs I think.

Confusedly,
Dave Conrad
dave%tygra@sharkey.cc.umich.edu
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