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Date:      Tue, 6 Jan 2004 16:30:36 +0100
From:      Harald Schmalzbauer <h@schmalzbauer.de>
To:        John Baldwin <jhb@FreeBSD.org>
Cc:        freebsd-current@FreeBSD.org
Subject:   Re: some HTT questions
Message-ID:  <200401061630.41005@harrymail>
In-Reply-To: <XFMail.20040106102129.jhb@FreeBSD.org>
References:  <XFMail.20040106102129.jhb@FreeBSD.org>

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On Tuesday 06 January 2004 16:21, John Baldwin wrote:
> On 06-Jan-2004 Harald Schmalzbauer wrote:
> > Hi all,
> >
> > I'm currently working on my first P4 ever.
> > I'm planning a colo production machine with FreeBSD 5.2 (RC2 atm).
> > The info of dmesg about the CPU shows:
> >
> > CPU: Intel(R) Pentium(R) 4 CPU 2.40GHz (2394.13-MHz 686-class CPU)
> >   Origin =3D "GenuineIntel"  Id =3D 0xf27  Stepping =3D 7
> >
> > Features=3D0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,=
PGE,
> >MCA,CMOV,PAT,PSE36,CLFLUS H,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
> >
> > So I think this CPU should be HyperThreading capable which gets hardened
> > by those lines:
> >
> >       acpi_cpu0: <CPU> on acpi0
> >       acpi_cpu1: <CPU> on acpi0
> >
> > But the next line gives my an error about CPU1:
> >
> >       device_probe_and_attach: acpi_cpu1 attach returned 6
> >
> > This line shows up a second time between probing of sio and nxp0.
> >
> > Ny my guess was that HTT should be enabled in the BIOS but the BIOS has
> > no entry about HTT.
> >
> > How can I use HTT and are my assumptions correct?
>
> Your assumptions are not correct. :)  If your CPU does support HTT, then
> the dmesg will include an extra line that says
> ' Hyperthreading: X logical cpus'.  The HTT Feature just means that we
> can check to see if this CPU has more than one core.  It might still

The Feature=3D<HTT> doesn't mean it supports HTT but means we are allowed t=
o=20
check if it supports HyperThreading??? Well that's total control.

Ok, then I have no HTT CPU and that's because the BIOS doesn't show the=20
HyperThreading menu.

Thanks all,

=2DHarry


> only have one core enabled, however.  Your BIOS has to support an HTT
> CPU, thus, ACPI has two cpu devices in case you do have a HTT CPU.
> However, only one is used in your system (acpi_cpu0) since your CPU
> does not support HTT.

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