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Date:      Tue, 11 May 1999 22:48:22 -0500 (EST)
From:      Alfred Perlstein <bright@rush.net>
To:        James Kalmadge <kalmadg@banet.net>
Cc:        Gurudatt Shenoy <gurudatt@cs.tamu.edu>, freebsd-questions@FreeBSD.ORG
Subject:   Re: 486 kernel works for 586?
Message-ID:  <Pine.BSF.3.96.990511224606.26546A-100000@cygnus.rush.net>
In-Reply-To: <3738E1C2.E088A614@banet.net>

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On Tue, 11 May 1999, James Kalmadge wrote:

> > On Tue, 11 May 1999, Gurudatt Shenoy wrote:
> >
> > >
> > > Hello,
> > > I compiled the FreeBSD 2.2.1 kernel on a Pentium class CPU with the CPU
> > > type set to "I486_CPU". However, when I boot the machine and try to use
> > > this kernel, I get "CPU class unknown" error.
> > > Won't a 486 kernel work on a "586" type CPU?
> > >
> > > I'd appreciate any feedback. Please reply to my email address - I am not
> > > on the FreeBSD list.
> > >
> >
> > MUST have the CPU type that you are going to use compiled in, there
> > is no "forward/backward compatibility" it just must have that type of
> > CPU compiled in.
> 
> To clarify:  I guess you are saying that  if you compile for multiple
> CPU types  you're all set.  Yes?
> As per:
> 
> cpu        "I486_CPU"
> cpu             "I586_CPU"
> cpu             "I686_CPU"
> 
> in the conf file.

Yup, it is important to note that taking out "I386_CPU" is VERY
important, it makes a lot of the kernel's lowest routines faster.

I'm unsure about I486, but if you can, I'd suggest removing it as
well.

-Alfred



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