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Date: Tue, 10 Oct 2006 13:59:39 -0400
To: Arthur Hartwig <arthur.hartwig@nokia.com>
From: Garance A Drosihn <drosih@rpi.edu>
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Subject: Re: Hyperthreading Issues (on Athlon64?)
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At 10:15 AM +1000 10/10/06, Arthur Hartwig wrote:
>ext kumaresh pandian wrote:
>>Hi all
>>   
>>   
>>   How do i Find if the CPU is Hyperthreading enabled or not? I have 
>>tried using the mtables but i'm not able to figure it out.
>>
>Look for the HTT bit in the CPU features displayed when FreeBSD starts
>up. Here's an example from one of my systems, HTT is third from the
>right hand end of the CPU features list.
>
>Copyright (c) 1992-2005 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.
>hartwig 1 10.09.2006-151040MPTable: <OEM ID   PRODUCT ID  >
>Timecounter "i8254" frequency 1193182 Hz quality 0
>CPU: Intel(R) Xeon(TM) CPU 2.80GHz (2794.59-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,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
>  Features2=0x4400<CNTX-ID,<b14>>
>  Hyperthreading: 2 logical CPUs
>real memory  = 2147483648 (2048 MB)
>avail memory = 2100936704 (2003 MB)

Huh.
I just got a dual-core Athlon64 machine, and the features list for
it says:

   Features=0x178bfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,
            MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,MMX,FXSR,SSE,SSE2,
            HTT>
            ---

My dmesg does not have the line about "Hyperthreading: 2 logical CPUs",
though.  But I had been pretty sure the Athlon64 chips didn't have any
hyperthreading support.  Why is the HTT there?

-- 
Garance Alistair Drosehn            =   gad@gilead.netel.rpi.edu
Senior Systems Programmer           or  gad@freebsd.org
Rensselaer Polytechnic Institute    or  drosih@rpi.edu