some HTT questions

[John Baldwin]

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
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.

-- 

John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/