Thanks for this additional input. Rather than reload the mobo bios, I rebuilt my machine (about three weeks ago) using a new mobo, cpu, etc, etc: after all the old one was old(ish). So I cannot comment on whether a bios upgrade would have cured the problem, sorry.
For what it's worth the new config seems fine and here is stuff from current sysinfo: SYSTEM INFORMATION Running Ubuntu Linux, the Ubuntu 13.04 (raring) release. GNOME: 3.6.3 (Ubuntu 2013-03-18) Kernel version: 3.8.0-32-generic (#47-Ubuntu SMP Tue Oct 1 22:35:23 UTC 2013) GCC: 4.7 (x86_64-linux-gnu) Xorg: 1.13.3 (16 October 2013 04:35:36PM) (16 October 2013 04:35:36PM) Uptime: 4 days 3 h 58 min CPU INFORMATION GenuineIntel, Intel(R) Core(TM) i5-4430 CPU @ 3.00GHz Number of CPUs: 4 CPU clock currently at 800.000 MHz with 6144 KB cache Numbering: family(6) model(60) stepping(3) Bogomips: 5985.82 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 syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf eagerfpu pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 fma cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm ida arat xsaveopt pln pts dtherm tpr_shadow vnmi flexpriority ept vpid fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid MEMORY INFORMATION Total memory: 7873 MB Total swap: 30576 MB HARDWARE INFORMATION MOTHERBOARD Host bridge Intel Corporation Haswell DRAM Controller (rev 06) Subsystem: Gigabyte Technology Co., Ltd Device 5000 PCI bridge(s) Intel Corporation Lynx Point PCI Express Root Port #1 (rev d5) (prog-if 00 [Normal decode]) Intel Corporation Lynx Point PCI Express Root Port #3 (rev d5) (prog-if 00 [Normal decode]) Intel Corporation 82801 PCI Bridge (rev d5) (prog-if 01 [Subtractive decode]) Intel Corporation 82801 PCI Bridge (rev 41) (prog-if 01 [Subtractive decode]) Intel Corporation Lynx Point PCI Express Root Port #1 (rev d5) (prog-if 00 [Normal decode]) Intel Corporation Lynx Point PCI Express Root Port #3 (rev d5) (prog-if 00 [Normal decode]) Intel Corporation 82801 PCI Bridge (rev d5) (prog-if 01 [Subtractive decode]) Intel Corporation 82801 PCI Bridge (rev 41) (prog-if 01 [Subtractive decode]) ISA bridge Intel Corporation Lynx Point LPC Controller (rev 05) Subsystem: Gigabyte Technology Co., Ltd Device 5001 GRAPHIC CARD VGA controller Intel Corporation Haswell Integrated Graphics Controller (rev 06) (prog-if 00 [VGA controller]) Subsystem: Gigabyte Technology Co., Ltd Device d000 SOUND CARD Multimedia controller Intel Corporation Lynx Point High Definition Audio Controller (rev 05) Subsystem: Gigabyte Technology Co., Ltd Device a002 NETWORK Ethernet controller Realtek Semiconductor Co., Ltd. RTL8111/8168 PCI Express Gigabit Ethernet controller (rev 06) Subsystem: Gigabyte Technology Co., Ltd Motherboard -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1229288 Title: 13.04 unity displays heashed output Status in “linux” package in Ubuntu: Incomplete Bug description: At some as yet undetermined user input, my screen 'hashes'... individual pixel lines become displaced by a few on a cyclic basis, so that the display becomes illegible. Note that this is an AMD64 machine with Nvidia graphics. I also experienced a problem a few days ago with some windows appearing completely black, but only when 'on top': the problems may be related. These problems have only appeared with Unity under Ringtail. None occurred with Gnome. --- ApportVersion: 2.9.2-0ubuntu8.3 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC0: hamiljf 2539 F.... pulseaudio CRDA: Error: command ['iw', 'reg', 'get'] failed with exit code 1: nl80211 not found. DistroRelease: Ubuntu 13.04 HibernationDevice: RESUME=UUID=28977afe-eff5-43ee-99ae-6219aa81ca15 InstallationDate: Installed on 2011-11-26 (668 days ago) InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111012) IwConfig: eth0 no wireless extensions. lo no wireless extensions. MachineType: Gigabyte Technology Co., Ltd. M61PME-S2 MarkForUpload: True NonfreeKernelModules: nvidia Package: linux (not installed) ProcFB: 0 VESA VGA ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.8.0-30-generic root=UUID=1e93934d-cb35-4bcc-b09d-eb95b1cb9eff ro vga=773 quiet splash ProcVersionSignature: Ubuntu 3.8.0-30.44-generic 3.8.13.6 RelatedPackageVersions: linux-restricted-modules-3.8.0-30-generic N/A linux-backports-modules-3.8.0-30-generic N/A linux-firmware 1.106 RfKill: Tags: raring Uname: Linux 3.8.0-30-generic x86_64 UpgradeStatus: Upgraded to raring on 2013-07-19 (67 days ago) UserGroups: adm admin cdrom dialout lpadmin plugdev sambashare WifiSyslog: dmi.bios.date: 03/07/2008 dmi.bios.vendor: Award Software International, Inc. dmi.bios.version: F2 dmi.board.name: M61PME-S2 dmi.board.vendor: Gigabyte Technology Co., Ltd. dmi.board.version: x.x dmi.chassis.type: 3 dmi.chassis.vendor: Gigabyte Technology Co., Ltd. dmi.modalias: dmi:bvnAwardSoftwareInternational,Inc.:bvrF2:bd03/07/2008:svnGigabyteTechnologyCo.,Ltd.:pnM61PME-S2:pvr:rvnGigabyteTechnologyCo.,Ltd.:rnM61PME-S2:rvrx.x:cvnGigabyteTechnologyCo.,Ltd.:ct3:cvr: dmi.product.name: M61PME-S2 dmi.sys.vendor: Gigabyte Technology Co., Ltd. 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