6 ms·

>Rule of thumb: On a desktop, if you have an i5 you do not have Hyperthreading. All i3s and i7s do have Hyperthreading, as do new Kaby Lake Pentiums (G4560, 460

>Rule of thumb: On a desktop, if you have an i5 you do not have Hyperthreading. All i3s and i7s do have Hyperthreading, as do new Kaby Lake Pentiums (G4560, 4600, 4620). Hmm...either this statement is wrong or this desktop /proc/cpinfo is wrong: $ grep -E 'model|stepping|cpu cores' /proc/cpuinfo | sort -u cpu cores : 4 model : 94 model name : Intel(R) Core(TM) i5-6600 CPU @ 3.30GHz stepping : 3 $ grep -q '^flags.*[[:space:]]ht[[:space:]]' /proc/cpuinfo && echo "Hyper-threading is supported" Hyper-threading is supported Intel's product spec page[1] lists this CPU as not supporting Hyper-Threading so I'm a bit puzzled as to why the ht flag is present. [1]https://ark.intel.com/products/88188/Intel-Core-i5-6600-Processor-6M-Cache-up-to-3_90-GHz https://ark.intel.com/products/88188/Intel-Core-i5-6600-Proc...

my123 9y ago
Do you have 8 threads?
justinclift 9y ago
Hmmm, checking for "ht" seems to be giving weird info. On a i5-750 here (few years old), running Fedora 25: $ grep '^flags.*[[:space:]]ht[[:space:]]' /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 syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf pni dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm sse4_1 sse4_2 popcnt lahf_lm tpr_shadow vnmi flexpriority ept vpid dtherm ida "ht" is being returned even though the CPU only has 4 cores and no hyperthreading: https://ark.intel.com/products/42915/Intel-Core-i5-750-Processor-8M-Cache-2_66-GHz https://ark.intel.com/products/42915/Intel-Core-i5-750-Proce... dmidecode seems to give more accurate info for this: $ sudo dmidecode -t processor | grep 'Count:' Core Count: 4 Thread Count: 4
- decisiveness 9y ago
  It looks like dmidecode also contradicts itself with the hyper threading flag: $ sudo dmidecode -t processor | grep -E 'Flags:|HTT|Status|Count' Flags: HTT (Multi-threading) Status: Populated, Enabled Core Count: 4 Thread Count: 4
  - justinclift 9y ago
    Hmmm... yeah that's showing the same on mine too. According to dmidecode, this CPU has hyperthreading.
strmpnk 9y ago
cpuinfo is probably wrong in this case. Looking at the intel spec sheet: http://ark.intel.com/products/88188/Intel-Core-i5-6600-Processor-6M-Cache-up-to-3_90-GHz http://ark.intel.com/products/88188/Intel-Core-i5-6600-Proce...
decisiveness 9y ago
To quote the Intel Developer Instructions[1] on the HTT flag: >A value of 0 for HTT indicates there is only a single logical processor in the package and software should assume only a single APIC ID is reserved. A value of 1 for HTT indicates the value in CPUID.1.EBX[23:16] (the Maximum number of addressable IDs for logical processors in this package) is valid for the package. UPDATE: It appears these flags refer to each initial APIC ID, so it seems the HTT flag value should be 0 in all cases where the overall processor:thread ratio is 1, suggesting there might either be incorrect information in the CPUID instruction for some Intel CPUs or the kernel is not correctly evaluating CPUID.1.EBX[23:16]. Hopefully, someone more versed in CPUs can correct me here. [1]https://www.intel.com/content/www/us/en/architecture-and-technology/64-ia-32-architectures-software-developer-manual-325462.html https://www.intel.com/content/www/us/en/architecture-and-tec...

my123 9y ago

Do you have 8 threads?

justinclift 9y ago

Hmmm, checking for "ht" seems to be giving weird info. On a i5-750 here (few years old), running Fedora 25: $ grep '^flags.*[[:space:]]ht[[:space:]]' /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 syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf pni dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm sse4_1 sse4_2 popcnt lahf_lm tpr_shadow vnmi flexpriority ept vpid dtherm ida "ht" is being returned even though the CPU only has 4 cores and no hyperthreading: https://ark.intel.com/products/42915/Intel-Core-i5-750-Processor-8M-Cache-2_66-GHz https://ark.intel.com/products/42915/Intel-Core-i5-750-Proce... dmidecode seems to give more accurate info for this: $ sudo dmidecode -t processor | grep 'Count:' Core Count: 4 Thread Count: 4

decisiveness 9y ago
It looks like dmidecode also contradicts itself with the hyper threading flag: $ sudo dmidecode -t processor | grep -E 'Flags:|HTT|Status|Count' Flags: HTT (Multi-threading) Status: Populated, Enabled Core Count: 4 Thread Count: 4
- justinclift 9y ago
  Hmmm... yeah that's showing the same on mine too. According to dmidecode, this CPU has hyperthreading.

strmpnk 9y ago

cpuinfo is probably wrong in this case. Looking at the intel spec sheet: http://ark.intel.com/products/88188/Intel-Core-i5-6600-Processor-6M-Cache-up-to-3_90-GHz http://ark.intel.com/products/88188/Intel-Core-i5-6600-Proce...

decisiveness 9y ago

To quote the Intel Developer Instructions[1] on the HTT flag: >A value of 0 for HTT indicates there is only a single logical processor in the package and software should assume only a single APIC ID is reserved. A value of 1 for HTT indicates the value in CPUID.1.EBX[23:16] (the Maximum number of addressable IDs for logical processors in this package) is valid for the package. UPDATE: It appears these flags refer to each initial APIC ID, so it seems the HTT flag value should be 0 in all cases where the overall processor:thread ratio is 1, suggesting there might either be incorrect information in the CPUID instruction for some Intel CPUs or the kernel is not correctly evaluating CPUID.1.EBX[23:16]. Hopefully, someone more versed in CPUs can correct me here. [1]https://www.intel.com/content/www/us/en/architecture-and-technology/64-ia-32-architectures-software-developer-manual-325462.html https://www.intel.com/content/www/us/en/architecture-and-tec...