I post here because I am using Ubuntu but this is probably an hardware problem. Since I bought my new setup with AMD Athlon(tm) II X4 635 Processor and asus m4a89td pro/usb3 motherboard with ecc ram I have stuttering on videos. I was using ubuntu 11.10 now ubuntu 12.10. Looking at syslog I have found that periodically (I notice only on videos but it happens always) this thing happens: Mar 6 23:36:42 virtual1 kernel: [28564.375548] smpboot: CPU 1 is now offline Mar 6 23:36:42 virtual1 kernel: [28564.380751] smpboot: CPU 2 is now offline Mar 6 23:36:42 virtual1 kernel: [28564.394947] smpboot: CPU 3 is now offline Mar 6 23:36:48 virtual1 kernel: [28569.917021] smpboot: Booting Node 0 Processor 1 APIC 0x1 Mar 6 23:36:48 virtual1 kernel: [28569.928015] LVT offset 0 assigned for vector 0xf9 Mar 6 23:36:48 virtual1 kernel: [28569.928372] [Firmware Bug]: cpu 1, try to use APIC500 (LVT offset 0) for vector 0x400, but the register is already in use for vector 0xf9 on another cpu Mar 6 23:36:48 virtual1 kernel: [28569.928378] perf: IBS APIC setup failed on cpu #1 Mar 6 23:36:48 virtual1 kernel: [28569.931305] process: Switch to broadcast mode on CPU1 Mar 6 23:36:48 virtual1 kernel: [28569.934255] smpboot: Booting Node 0 Processor 2 APIC 0x2 Mar 6 23:36:48 virtual1 kernel: [28569.945554] [Firmware Bug]: cpu 2, try to use APIC500 (LVT offset 0) for vector 0x400, but the register is already in use for vector 0xf9 on another cpu Mar 6 23:36:48 virtual1 kernel: [28569.945558] perf: IBS APIC setup failed on cpu #2 Mar 6 23:36:48 virtual1 kernel: [28569.948124] process: Switch to broadcast mode on CPU2 Mar 6 23:36:48 virtual1 kernel: [28569.949644] smpboot: Booting Node 0 Processor 3 APIC 0x3 Mar 6 23:36:48 virtual1 kernel: [28569.960838] [Firmware Bug]: cpu 3, try to use APIC500 (LVT offset 0) for vector 0x400, but the register is already in use for vector 0xf9 on another cpu Mar 6 23:36:48 virtual1 kernel: [28569.960840] perf: IBS APIC setup failed on cpu #3 Mar 6 23:36:48 virtual1 kernel: [28569.962953] process: Switch to broadcast mode on CPU3 I have: updated bios; tried all (really) bios options; changed ram; changed psu and cpu cooler; tried 3.8.1 kernel. What can I do now? Please help me! Thanks, Mario