some HTT questions

[Harald Schmalzbauer]

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 = "GenuineIntel"  Id = 0xf27  Stepping = 7
> >
> > Features=0xbfebfbff<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=<HTT> doesn't mean it supports HTT but means we are allowed to 
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 
HyperThreading menu.

Thanks all,

-Harry


> 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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