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Date:      Wed, 20 Dec 2000 20:00:39 +0100
From:      Francesco Casadei <fcasadei@inwind.it>
To:        Jeremiah Gowdy <jgowdy@home.com>
Cc:        freebsd-questions@FreeBSD.ORG
Subject:   Re: FreeBSD 4.1 & 3DNOW! - And other Kernel/CPU questions
Message-ID:  <20001220200039.A1340@goku.kasby>
In-Reply-To: <001b01c06ab2$ff751500$aa240018@cx443070b>; from jgowdy@home.com on Wed, Dec 20, 2000 at 10:30:58AM -0800
References:  <006a01c062db$d7a134c0$0100a8c0@mshome.net> <20001220191014.A598@goku.kasby> <001b01c06ab2$ff751500$aa240018@cx443070b>

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On Wed, Dec 20, 2000 at 10:30:58AM -0800, Jeremiah Gowdy wrote:
> > Sorry for the late post, but I couldn't read the mailing list last week.
> >
> > I have an AMD K6-2 3D 300 MHz processor. I think we can't have 3DNOW!
> > optimization enabled in the kernel (and it would be useless for the
> > performance, I think) but you can enable the following options in the
> kernel
> > config file:
> >
> > machine   i386
> > cpu       I586_CPU
> >
> > options  CPU_FASTER_5X86_FPU   #Enables a faster FPU exception handler
> > options  CPU_SUSP_HLT          #Enables suspend on the HALT instruction
> > options  CPU_WT_ALLOC          #Enables write allocation on AMD K6-2
> > options  NO_F00F_HACK          #Not a iPentium
> > options  NO_MEMORY_HOLE        #15-16MB range not occupied by ISA memory
> hole
> 
> Um, having 3D-Now! (SIMD) instructions, the K6-2 is most certainly an MMX
> processor, so why aren't you using cpu I686_CPU ?
> 
> 
> I've always been somewhat curious on this.  Can we more explicitly label
> what is 586 and 686 ?  Pentium (P54C), Pentium MMX, Pentium Pro, Pentium II,
> Celeron, Pentium III, Pentium IV, AMD K5, AMD K6, AMD K6-2, AMD K6-3, AMD
> Athlon K7, AMD Athlon Thunderbird, AMD Duron, WinChips etc are ALL piled in
> that group somewhere.  I always considered it to be, 586 = No MMX, 686 = Yes
> MMX, the exception being PPro, which I would call 686.  Someone with a
> little more knowledge of the kernel optimizations help us out here ?
> 
> 
> 
> 
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> 
> end of the original message

The answer is simple:

casimiro> dmesg
Copyright (c) 1992-2000 The FreeBSD Project.
Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994
        The Regents of the University of California. All rights reserved.
FreeBSD 4.2-STABLE #0: Mon Dec  4 03:16:09 CET 2000
    root@goku.kasby:/usr/obj/usr/src/sys/GOKU
Timecounter "i8254"  frequency 1193182 Hz
CPU: AMD-K6(tm) 3D processor (297.68-MHz 586-class CPU)
                                         ^^^^^^^^^^^^^
  Origin = "AuthenticAMD"  Id = 0x580  Stepping = 0
  Features=0x8001bf<FPU,VME,DE,PSE,TSC,MSR,MCE,CX8,MMX>
  AMD Features=0x80000800<SYSCALL,3DNow!>
[...]

I tried to compile the kernel with "cpu I686_CPU", but the kernel did not even
boot!

	Francesco Casadei




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