 One review in 2010 found improvements on the order of 9% (on average) with NCQ enabled in a series of Windows multitasking tests.NCQ can negatively interfere with the operating system's I/O scheduler, actually decreasing performance; this has been observed in practice on Linux with RAID-5.There is no mechanism in NCQ for the host to specify any sort of deadlines for an I/O, like how many times a request can be ignored in favor of others.