Lower numbers result in faster bus-turnaround and, thus, better performance.
If the idle-park bit is disabled, the memory command bus will be parked on CAS READ, which results in a zero latency on the next read command. Turnaround between the last Write Data Phase until a precharge command can be issued. The ALi M1647 controller does not measure page hits but relies on bus cycles to determine the expiration of a page. Disabling the force-flushing can increase performance but also bears the inherent risk of data corruption. For more detailed descriptions of some of the parameters please check the LostCircuits BIOS guide.