[lfs-support] Can anybody illuminate this curiosity

Paul Rogers paulgrogers at fastmail.fm
Sun Aug 21 16:27:44 PDT 2016


I've been given a Core-2 Quad Extreme.  Lately I've been considering
putting it in service.  Essentially this is two over-clocked Conroes on
one chip, 130 W TDP!  That's equivalent to my i7-940, and it's got extra
hyperthreading.  Heat's the chip killer, so I figure I need to start
looking into CPU frequency scaling--never an issue before on all
desktops--
and discovered a curiosity.  So I started with this Conroe I use every
day.  Intel says these Core-2 Duo's don't DO hyperthreading.

[16:05 ~]# grep flags /proc/cpuinfo
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 nx
lm constant_tsc arch_perfmon pebs bts aperfmperf pni dtes64 monitor
ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm lahf_lm dtherm tpr_shadow
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 nx
lm constant_tsc arch_perfmon pebs bts aperfmperf pni dtes64 monitor
ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm lahf_lm dtherm tpr_shadow

ht flag is for hyperthreading!  With hyperthreading enabled in the
kernel, cpuinfo, and top, both say I have only 2 CPUs.  But with cpufreq
also enabled, I saw these while I was checking my cpufreq configuration:

[16:11 ~]# cat /sys/devices/system/cpu/possible
0-3
[16:12 ~]# cat /sys/devices/system/cpu/online
0-1
[16:12 ~]# cat /sys/devices/system/cpu/offline
2-3

It looks like, in shades of the "good old days", some artifact of the
chip
manufacture or *marketing* suggests the CORE-2 Duo was supposed to do HT
but maybe it didn't work, or have four cores but two of them have been
disabled!  :o

Anybody got a line on what's going on here?

-- 
Paul Rogers
paulgrogers at fastmail.fm
Rogers' Second Law: "Everything you do communicates."
(I do not personally endorse any additions after this line. TANSTAAFL
:-)

-- 
http://www.fastmail.com - Same, same, but different...



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