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From: Pete French <petefrench@ticketswitch.com>
Date: Fri, 27 Jan 2006 10:16:06 +0000
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Subject: How do I turn off hyperthreading on 6.0 ?
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I though that machdep.hyperthreading_allowed had to be set to 1 to
turn on hyperthreading ? I have a dual processor HP blade, and
when I boot it up with an SMP kernel I get 4 CPU's. Setting that flag
does not have any effect!

Any thoughts ? I dont think I have two CPU's each with dual
core and without hyperthreading somehow! (though the thought did cross
my mind...)

webadmin@websvr04$ sysctl machdep.hyperthreading_allowed
machdep.hyperthreading_allowed: 0


CPU: Intel(R) Xeon(TM) CPU 3.60GHz (3600.14-MHz 686-class CPU)
  Origin = "GenuineIntel"  Id = 0xf43  Stepping = 3
  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=0x659d<SSE3,RSVD2,MON,DS_CPL,EST,TM2,CNTX-ID,CX16,<b14>>
  AMD Features=0x20000000<LM>
  Hyperthreading: 2 logical CPUs
real memory  = 3758043136 (3583 MB)
avail memory = 3678736384 (3508 MB)
ACPI APIC Table: <HP     00000083>
FreeBSD/SMP: Multiprocessor System Detected: 4 CPUs
 cpu0 (BSP): APIC ID:  0
 cpu1 (AP): APIC ID:  1
 cpu2 (AP): APIC ID:  6
 cpu3 (AP): APIC ID:  7