From: Steven Rostedt I'm trying to get the nmi working with my laptop (IBM ThinkPad G41) and after debugging it a while, I found that the nmi code doesn't want to set it up for this particular CPU. Here I have: $ cat /proc/cpuinfo processor : 0 vendor_id : GenuineIntel cpu family : 15 model : 4 model name : Mobile Intel(R) Pentium(R) 4 CPU 3.33GHz stepping : 1 cpu MHz : 3320.084 cache size : 1024 KB physical id : 0 siblings : 2 core id : 0 cpu cores : 1 fdiv_bug : no hlt_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 3 wp : yes 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 pni monitor ds_cpl est tm2 cid xtpr bogomips : 6642.39 processor : 1 vendor_id : GenuineIntel cpu family : 15 model : 4 model name : Mobile Intel(R) Pentium(R) 4 CPU 3.33GHz stepping : 1 cpu MHz : 3320.084 cache size : 1024 KB physical id : 0 siblings : 2 core id : 0 cpu cores : 1 fdiv_bug : no hlt_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 3 wp : yes 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 pni monitor ds_cpl est tm2 cid xtpr bogomips : 6637.46 And the following code shows: $ cat linux-2.6.13-rc6/arch/i386/kernel/nmi.c [...] void setup_apic_nmi_watchdog (void) { switch (boot_cpu_data.x86_vendor) { case X86_VENDOR_AMD: if (boot_cpu_data.x86 != 6 && boot_cpu_data.x86 != 15) return; setup_k7_watchdog(); break; case X86_VENDOR_INTEL: switch (boot_cpu_data.x86) { case 6: if (boot_cpu_data.x86_model > 0xd) return; setup_p6_watchdog(); break; case 15: if (boot_cpu_data.x86_model > 0x3) return; Here I get boot_cpu_data.x86_model == 0x4. So I decided to change it and reboot. I now seem to have a working NMI. So, unless there's something know to be bad about this processor and the NMI. I'm submitting the following patch. Signed-off-by: Steven Rostedt Acked-by: Zwane Mwaikambo Signed-off-by: Andrew Morton --- arch/i386/kernel/nmi.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) diff -puN arch/i386/kernel/nmi.c~mobil-pentium-4-ht-and-the-nmi arch/i386/kernel/nmi.c --- devel/arch/i386/kernel/nmi.c~mobil-pentium-4-ht-and-the-nmi 2005-08-18 21:14:53.000000000 -0700 +++ devel-akpm/arch/i386/kernel/nmi.c 2005-08-18 21:14:53.000000000 -0700 @@ -195,7 +195,7 @@ static void disable_lapic_nmi_watchdog(v wrmsr(MSR_P6_EVNTSEL0, 0, 0); break; case 15: - if (boot_cpu_data.x86_model > 0x3) + if (boot_cpu_data.x86_model > 0x4) break; wrmsr(MSR_P4_IQ_CCCR0, 0, 0); @@ -432,7 +432,7 @@ void setup_apic_nmi_watchdog (void) setup_p6_watchdog(); break; case 15: - if (boot_cpu_data.x86_model > 0x3) + if (boot_cpu_data.x86_model > 0x4) return; if (!setup_p4_watchdog()) _