BOOT_IMAGE=/boot/vmlinuz-3.16.0-4-amd64 root=UUID=cc17d4be-6875-4daa-965f-329ca3d66049 ro nolapic splash
Well, it's not "acpi=off", but still, the result's similar. The LAPIC is a Local Advanced Programmable Interrupt Controler. It basically handles interrupts and multi-core functionality. Having the "nolapic" option enabled you basically limit yourself to a single core/CPU. Many people use it to bypass problems with their system hanging at boot (mostly due to Kernel Mode Setting problems, which can be a pain... :/ ).
Here's what you can do to test it out. When booting, in GRUB, before choosing an option to boot (or letting GRUB do that for you after the 5 seconds timeout), select the option you want to boot (most probably the first on the list) and press the "e" key. Find the line that ends with "ro nolapic splash" (you'll probably need to scroll a bit) and remove the "nolapic" part. After that press F10 to boot the edited config. If the system boots without problems, check if you have all your cores visible and active. If so, then we'll make this setup permanent in the next posts (don't have my Sparky environment with me right now and I don't want to advise on such things out of my head - too risky