Clock
The main system clock is 24MHz. It is then divided by NEO-D0 to 12MHz for the 68k, 6MHz for the GPU and 1MHz (?).
LSPC2-A2 divides the 24MHz clock to 8MHz for the YM2610 and 4MHz for the Z80.
NEO-GRC does this on the NeoGeo CD ?
A second quartz is used on NeoGeo systems for generating the color burst frequency for the video encoders.