Would probably depend on the drive. There were utils out there in DOS land that let you format higher than normal. Usually by playing with the sector/track sizes. But it depended on the drive to let you do it. The best I ever got was ~1.6 out of my drives/media.
The trick works by using the double sampling rate to inspect the normal data rate disk surface. When the disk surface already has a double data rate, the drive doesn't have a quadruple data rate mode to be able to read it.
