Very Computer

Hi,

my cpuinfo includes the 'ht' flag, although I do not have a processor
with Hyper Threading, nor a kernel supporting this. How come?

$ cat /proc/cpuinfo
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 15
model           : 2
model name      : Intel(R) Pentium(R) 4 CPU 2.80GHz
stepping        : 9
cpu MHz         : 2793.374
cache size      : 512 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 2
wp              : yes
flags           : 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 ht tm pbe cid
bogomips        : 5521.40
$ uname -a
Linux topjaklont.student.utwente.nl 2.6.5 #3 Thu Apr 22 19:00:30 CEST 2004 i686 i686 i386 GNU/Linux

yours,
Gerrit.

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On Thu, 22 Apr 2004 17:17:19 UTC in comp.os.linux.hardware, Gerrit Holl

I think you have to search quite hard to find an Intel processor that _doesn't_
support HT nowadays. Yours says it does in the capabilities bits (which is
what's decoded as the flags field here). You can also check the output from
dmesg where it puts out the processor capabilities bitmask as 4 bytes of hex.
You can then look at the bit settings yourself and compare them with the
documented return from the cpuid instruction.

Ah, the Intel "IA-32 Intel architecture software developer's manual: vol 3:
system programming guide" (25366813.pdf) says that after issuing a cpuid
instruction with EAX=1

"The Hyperthreading technology feature flag (bit 28 in EDX) indicates (when set)
that the processor is capable of supporting HT technology.

Bits 16 through 23 in the EBX register indicate the number of logical processors
supported within the physical package.

It is possible to have the CPUID feature flag set indicating a processor is
capable of supporting HT technology when only one logical processor is available
in the package. In this case bits 16 through 23 in the EBX register will have a
value of 1."

--
Trevor Hemsley, Brighton, UK.

<posted & mailed>

Gerrit Holl wrote in comp.os.linux.hardware:

Quote:> Hi,

> my cpuinfo includes the 'ht' flag, although I do not have a processor
> with Hyper Threading, nor a kernel supporting this. How come?

[snip]

As far as I can tell, the 'ht' flag does not mean that the chip has ht.  
It only means that when you ask the chip how many processors it has
you will get a sensible answer (which could be one).

--
Sig goes here...
Peter D.