Core limitation for a 32bit centOS

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Core limitation for a 32bit centOS

Post by kalraguarav85 » 2019/08/19 13:17:34


I am using a Intel(R) Xeon(R) CPU E5-2697 v3 @ 2.60GHz machine, with 28 physical cores (2 sockets and 14 cores per socket).
But, when I install a 32 bit centOS 7 version on this machine, I can see only 8 cores. Is there any such limitation for a 32 bit OS, as with 64bit centOS, I can see all 28 cores available.

Can someone please help on this. Below are the OS Version details and lscpu output.

CentOS Version:
NAME="CentOS Linux"
VERSION="7 (AltArch)"
ID_LIKE="rhel fedora"
PRETTY_NAME="CentOS Linux 7 (AltArch)"


lscpu output:
Architecture: i686
CPU op-mode(s): 32-bit, 64-bit
Byte Order: Little Endian
CPU(s): 8
On-line CPU(s) list: 0-7
Thread(s) per core: 1
Core(s) per socket: 4
Socket(s): 2
Vendor ID: GenuineIntel
CPU family: 6
Model: 63
Model name: Intel(R) Xeon(R) CPU E5-2697 v3 @ 2.60GHz
Stepping: 2
CPU MHz: 1199.960
CPU max MHz: 3600.0000
CPU min MHz: 1200.0000
BogoMIPS: 5200.16
Virtualization: VT-x
L1d cache: 32K
L1i cache: 32K
L2 cache: 256K
L3 cache: 35840K
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 pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts xtopology nonstop_tsc aperfmperf eagerfpu pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 fma cx16 xtpr pdcm pcid dca sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm epb tpr_shadow vnmi flexpriority ept vpid fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid cqm xsaveopt cqm_llc cqm_occup_llc dtherm ida arat pln pts

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Re: Core limitation for a 32bit centOS

Post by avij » 2019/08/19 13:24:59

Yes, there is a limitation. Use the x86_64 version of CentOS on such machines.

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Re: Core limitation for a 32bit centOS

Post by TrevorH » 2019/08/19 13:31:29

You'll also find that RAM access is either restricted or considerably slower than on the 64 bit version. A 32 bit o/s has to use PAE to address more than 4GB RAM and I can no longer remember if the CentOS 7 kernel has PAE enabled by default - in which case all RAM will be seen but access to it will be slower than if using a 64 bit o/s - or if it's disabled by default in which case you'll only be able to use a maximum of 4GB RAM minus whatever is required for hardware, usually working out at around 3.6GB available.
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