I'm having some issues with a Yosemite installation that I've been beating my head against the wall for a few days now, and it's completely stuck.
After I did the combo update to 10.10.3, whenever I put in the following boot flags: -v -f GraphicsEnabler=No PCIRootUID=1 (or 0) npci=0x3000 cpus=1
it automatically reboots. It does this no matter what combination I put the boot flags in. I've also tried nv_disable=1 and 0 and those do not work either. I'm really getting frustrated with this and am about to do a rollback install to 10.10.10
NVIDIA GTX 760 4GB (HDMI)
12 GB Ram
ASUS 990FX R2.0 (No Integrated Graphics)