JEELABS did a nice WS2812B LED Driver Project that uses an ARM LPC810 running at 30 MHz to get things done.
“Sending 12 bits @ 2.4 MHz takes 5 microseconds. If we were to set the LPC810 to run at its maximum 30 MHz clock, we could probably drive the SPI hardware entirely via interrupts, but for a simple timed example this is not really necessary. Instead, we can let the SysTick timer interrupt the polling loop used to drive the SPI bus – without losing track of time.”