Description of problem: Motherboard: Intel server board SE7501BR2. 2 X CPU, Xeon 2.8GHZ. Intel shows SE7501BR2 supports RedHat 8.0. RedHat shows RedHat Linux 8.0 supports Intel SE7501BR2. When booting the machine, BIOS shows the following: ------------ AMIBIOS (C)1985-2002 American Megatrends Inc., Copyright 1996-2002 Intel Corporation SBR20.86B.0043.P02.0212131401 SBR2 Production BIOS Version 1.00 BIOS Build 0043 2 X Intel(R) Xeon(TM) CPU 2.80GHz 533MHz Front Side Bus Testing system memory, memory size=1024MB 1024MB Extended Memory Passed 512K L2 Cache SRAM Passed Legacy Keyboard .... Detected Legacy Mouse ....... Detected USB Legacy ......... Enabled Entering boot selection menu... ------------ But, "dmesg" shows: --------------------- 00000000 00000000, vendor = 0 CPU: L1 I cache: 0K, L1 D cache: 8K CPU: L2 cache: 512K CPU: Physical Processor ID: 0 CPU: After vendor init, caps: bfebfbff 00000000 00000000 00000000 Intel machine check reporting enabled on CPU#1. CPU: After generic, caps: bfebfbff 00000000 00000000 00000000 CPU: Common caps: bfebfbff 00000000 00000000 00000000 CPU1: Intel(R) Xeon(TM) CPU 2.80GHz stepping 07 Booting processor 2/6 eip 2000 Initializing CPU#2 masked ExtINT on CPU#2 ESR value before enabling vector: 00000000 ESR value after enabling vector: 00000000 Calibrating delay loop... 5573.87 BogoMIPS CPU: Before vendor init, caps: bfebfbff 00000000 00000000, vendor = 0 CPU: L1 I cache: 0K, L1 D cache: 8K CPU: L2 cache: 512K CPU: Physical Processor ID: 3 CPU: After vendor init, caps: bfebfbff 00000000 00000000 00000000 Intel machine check reporting enabled on CPU#2. CPU: After generic, caps: bfebfbff 00000000 00000000 00000000 CPU: Common caps: bfebfbff 00000000 00000000 00000000 CPU2: Intel(R) Xeon(TM) CPU 2.80GHz stepping 07 Booting processor 3/7 eip 2000 Initializing CPU#3 masked ExtINT on CPU#3 ESR value before enabling vector: 00000000 ESR value after enabling vector: 00000000 Calibrating delay loop... 5573.87 BogoMIPS CPU: Before vendor init, caps: bfebfbff 00000000 00000000, vendor = 0 CPU: L1 I cache: 0K, L1 D cache: 8K CPU: L2 cache: 512K CPU: Physical Processor ID: 3 CPU: After vendor init, caps: bfebfbff 00000000 00000000 00000000 Intel machine check reporting enabled on CPU#3. CPU: After generic, caps: bfebfbff 00000000 00000000 00000000 CPU: Common caps: bfebfbff 00000000 00000000 00000000 CPU3: Intel(R) Xeon(TM) CPU 2.80GHz stepping 07 Total of 4 processors activated (22259.09 BogoMIPS). -------------------- Version-Release number of selected component (if applicable):kernel-2.4.18-14smp How reproducible: Everytime Steps to Reproduce: 1.Install Red Hat Linux 8.0 on SE7501BR2 with 2 processors 2.Every time the machine is booted, "dmesg" shows 4 processors. Actual results: "dmesg" shows 4 processors. Is the OS using four processors, or one? Expected results: "dmesg" should show 2 processors as BIOS does. Additional info: It happens with both GRUB and LILO.
This is expected. XEON CPUs (meaning those with the marketing name XEON not the extention XEON eg. Pentium III XEON) have two processing units per physical unit. This means that for every CPU the Linux kernel counts two, so 2 CPUs * 2 units = 4. While it's not quite the same as a four CPU SMP system there are similarities; the limitation of this setup is that for every two cpu's you share the cache and other lines. Intel calls this technology Hyper-Threading. If you would like to verify that your CPUs contain the Hypter-Threading technology you can check the flags under /proc/cpuinfo where you see things like 'mmx' and 'sse2'; there should also be an 'ht' flag.