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From: psfales@ihlpe.ATT.COM (Peter Fales)
Newsgroups: comp.sys.ibm.pc
Subject: Re: How do you detect a V20?
Message-ID: <1710@ihlpe.ATT.COM>
Date: Fri, 24-Apr-87 22:17:35 EDT
Article-I.D.: ihlpe.1710
Posted: Fri Apr 24 22:17:35 1987
Date-Received: Sun, 26-Apr-87 20:18:45 EDT
References: <785@killer.UUCP>
Organization: AT&T Bell Laboratories - Naperville, Illinois
Lines: 21
Keywords: NEC V20/V30, software detection?
Summary: Yes, but it's not easy!

In article <785@killer.UUCP>, toma@killer.UUCP (Tom Armistead) writes:
> Is there a way to detect a NEC V20 or V30 CPU in an IBM or compatible PC
> through software???

I have an assembly language program (that came originally from netnews)
that does exactly that.  The V20/V30 are so compatible that software
differentiation is difficult.  The trick is to use a bug in the Intel
chips that was fixed in the NEC chips.  Namely: If a hardware interrupt
occurs during a string instruction prefaced by a repeat instruction, when
control is returned to the instruction the Intel chips "forget" about
the repeat instruction.  The NECs do not.

The program CPUID.ASM/CPUID.COM is available on some BBS systems or
I can mail or post copies if anyone is interested.  It can figure out
whether you have an 8088, 8086, 80188, 80186, V20, V30, or 80286, and
whether the math coprocessor is installed.
-- 
Peter Fales		UUCP:	...ihnp4!ihlpe!psfales
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