https://community.hpe.com/t5/operating-system-linux/how-to-get-kernel-to-recognize-added-cpu/m-p/3107862#M7600 Although the details varied ever so slightly, Jerome's answer was right on (and something I should have remembered - DOH!).<BR /><BR />Resolved by setting BIOS as follows...<BR /><BR />Advanced Settings, MPS Table Mode:<BR /> Full Table APIC &lt;- correct for SMP<BR /> Full Table Mapped<BR /> Disabled &lt;- was set here before<BR /> Auto Set Table<BR /><BR />Since the CPU's are hyperthreaded, "top" now shows 4 CPU's.<BR /><BR />Thanks again.<BR /><BR />-Jared<BR /> Sat, 01 Nov 2003 14:42:05 GMT Jared Middleton 2003-11-01T14:42:05Z https://community.hpe.com/t5/operating-system-linux/how-to-get-kernel-to-recognize-added-cpu/m-p/3107860#M7598 Server:<BR /> Compaq ProLiant DL380 G3<BR /> 1 Intel Xeon 2.4GHz CPU<BR /> Red Hat Linux 7.3 Professional<BR /> kernel: 2.4.20-20.7<BR /><BR />Just added a second matching 2.4GHz CPU. Upon cold boot, the system BIOS immediately recognized the additional CPU, but linux does not seem to.<BR /><BR />I downloaded the latest SMP kernel from Red Hat (2.4.20-20.7smp), installed the RPM, modified GRUB to use it, and rebooted.<BR /><BR />However, "top" does not show the new CPU.<BR /><BR />$ uname -a<BR />Linux myserv 2.4.20-20.7smp #1 SMP Mon Aug 18 14:46:14 EDT 2003 i686 unknown<BR /><BR />I'm not sure what needs to be tweaked.<BR />Any help would be appreciated. Fri, 31 Oct 2003 20:24:03 GMT https://community.hpe.com/t5/operating-system-linux/how-to-get-kernel-to-recognize-added-cpu/m-p/3107860#M7598 Jared Middleton 2003-10-31T20:24:03Z https://community.hpe.com/t5/operating-system-linux/how-to-get-kernel-to-recognize-added-cpu/m-p/3107861#M7599 Hi,<BR /><BR />Check your BIOS :<BR />1. Press F10 when the server boots to enter the System Configuration Utility<BR />2. Press Enter to dismiss the splash screen<BR />3. Immediately press CTRL+A<BR />4. A message will appear informing you that you are now in "Advanced Mode"<BR />5. Then select "Configure Hardware" -&gt; "View / Edit details"<BR />6. You will then see the advanced settings (intermixed with the ordinary ones)<BR />7. Stroll down to "APIC Mode" and then select "Fully Mapped"<BR />8. Save changes and reboot<BR />9. Tell us...<BR /><BR />hth<BR /><BR />J<BR /> Sat, 01 Nov 2003 05:09:27 GMT https://community.hpe.com/t5/operating-system-linux/how-to-get-kernel-to-recognize-added-cpu/m-p/3107861#M7599 Jerome Henry 2003-11-01T05:09:27Z https://community.hpe.com/t5/operating-system-linux/how-to-get-kernel-to-recognize-added-cpu/m-p/3107862#M7600 Although the details varied ever so slightly, Jerome's answer was right on (and something I should have remembered - DOH!).<BR /><BR />Resolved by setting BIOS as follows...<BR /><BR />Advanced Settings, MPS Table Mode:<BR /> Full Table APIC &lt;- correct for SMP<BR /> Full Table Mapped<BR /> Disabled &lt;- was set here before<BR /> Auto Set Table<BR /><BR />Since the CPU's are hyperthreaded, "top" now shows 4 CPU's.<BR /><BR />Thanks again.<BR /><BR />-Jared<BR /> Sat, 01 Nov 2003 14:42:05 GMT https://community.hpe.com/t5/operating-system-linux/how-to-get-kernel-to-recognize-added-cpu/m-p/3107862#M7600 Jared Middleton 2003-11-01T14:42:05Z https://community.hpe.com/t5/operating-system-linux/how-to-get-kernel-to-recognize-added-cpu/m-p/3107863#M7601 Glad it worked !<BR /><BR />Sorry for the imprecision on the process. I do not have this machine, had to rely on HP online manual, which is quite imprecise about BIOS setup !<BR /><BR />J Sun, 02 Nov 2003 08:12:21 GMT https://community.hpe.com/t5/operating-system-linux/how-to-get-kernel-to-recognize-added-cpu/m-p/3107863#M7601 Jerome Henry 2003-11-02T08:12:21Z