FAQ: CPU / FPS Limiter, EQCPU, MQ2FPS

[Lax]

Definitions
FPS Limiter: Limits framerate by calculating the current frames per second (video display), and slows it down if it goes over a certain rate.
CPS Limiter: Reduces CPU usage by a set amount.

EQCPU vs MQ1 vs MQ2
EQCPU - CPU Limiter
MQ1 - CPU Limiter
MQ2FPS - FPS Limiter in "calculate" mode, or CPU Limiter in "absolute" mode.

Behavior during macros
EQCPU - No macros, because you cannot run MQ1 or MQ2 while using EQCPU.
MQ1 - MQ1 pulse behavior is crazy. I dont even want to think about how it really works, but the CPU limiter does absolutely nothing during critical macros. If it does, it will give up CPU between every macro command... It normally doesn't Sleep(0) which would give up enough CPU time for the rest of the system to run properly. Instead, the entire system fights viciously for CPU time the same as if the CPU limiter was not implemented into MQ1.
MQ2FPS - MQ2 pulse behavior is a little more geared toward not doing too much when multiple macro commands should run (turbo), etc. MQ2FPS will always give up enough CPU time to let the rest of the system function properly, whether macros are running or not. During macro execution, the FPS indicator will show /MACRO as the maximum amount, instead of a number. This indicates that the FPS/CPU limiter is sleeping only enough for the rest of the system to run, not what you would normally want it to do otherwise.

MQ2FPS options -- deciding whether you need absolute or calculate
"absolute" mode is a straight CPU limiter. When not running macros, it will always give up the same amount of CPU time and therefore the CPU usage will drop to a constant percentage -- 33%, 50%, 66%, whatever you pick your settings to drop it to. If you want to limit your CPU usage to a specific amount per EQ session, this is what you want.
"calculate" mode is an FPS limiter. If your framerate goes above x amount per second, MQ2FPS calculates how much processor time it should give up, and gives up that amount. It will ALWAYS give up CPU time, even if it is minimal. This means your background applications will always be able to use the CPU without fighting for time, even if the CPU usage is at 99% otherwise. If you're not concerned about your CPU usage being at 99%, and you just want EQ not to uselessly go above a certain framerate, this is what you want.
MQ2FPS defaults to "calculate" mode. To switch, use the /fps command.