I too am experiencing this problem on my new build on both windows 8.1 and windows 10 on all builds versions of cubase 8.0.x with the first release 8.0.0 being the least affected by ASIO spikes. I also experience spikes with other onscreen actions such as dragging around audio/midi events, changing event volume via mouse wheel or click and hold and other mouse orientated editing tools/practices. I have performed an intensive amount of trial and error and trouble shooting regarding these issues with little (rare) or no (mostly) reduction in spike occurrences. My problems or cause of seems to be outlined in several other posts across this forum. I have reduced it to 3 main causes to the spikes
editing tools mainly scissors and pencil as well as time stretching/selection tool
graphically intensive elements (dragging events whereby transparency shaders of events is involved)
USB drives being inserted (results in a pulsing spike)
The reasoning behind these actions are mainly to do with having an on board graphics adapter (Intel HD5500) which I will be able to test out tomorrow via use of an external 750ti geforce (may cause its own problems and woes being setup externally) but is my only option with my current new build as it is a gigabyte brix. The other has to do with the usb pcie host controller gigabyte has chosen to use in there build. (Also attempting to fix via a different brand usb 2.0 adapter card that I will be slotting into one of the MSATA slots - should arrive in the next week sometime).
I’ve currently exhausted almost every driver combination ranging from early releases to the latest from both manufacturer and generic/Microsoft standard. Tried novel system tweaks such as disabling dynamic ticks and page file removal/preset amounts to the ones outlined on this site and native instruments regarding power/appearance/bios settings to do with speed stepping/turbo mode and disabling/removing hardware that isn’t essential to the operation of the system.
My system specs are:
Intel broadwell chipset 5500 with 2.4ghz
Onboard broadwell HD5500 graphics
Samsung EVO 850 500gb SSD <—OS & DAW installed on here
Western Digital 1tb secondary drive <-----Projects stored on this one
Kingston Hyperx DDR3 Dual Channel 16gb RAM timing 9-9-9-27
Wifi card removed
Gigabyte LAN disabled in bios
Furthermore ever update since the primary release of 8.0.0 has resulted in accumulating amount of cpu consumption in projects. Have tested with both windows 8.1x64 and windows 10x64 CLEAN installs with nothing but base drivers installed and cubase 8 with no 3rd party plugins on a 64bit build. Testing has been carried out over the last 2 months now almost daily… Am at the end of my sanity and am thinking I will have to sell the brix and build another system with a dedicated graphics card. A pity as the sound level/power and size of the brix made it a great computer and am otherwise very pleased with it.