Index: ata_kauai.c
===================================================================
--- ata_kauai.c	(revision 190194)
+++ ata_kauai.c	(working copy)
@@ -365,6 +365,9 @@
 	struct ata_device *atadev = device_get_softc(request->dev);
 	struct ata_kauai_softc *sc = device_get_softc(request->parent);
 
+	if (request->flags & ATA_R_ATAPI && request->bytecount % 16 != 0)
+		request->flags &= ~ATA_R_DMA;
+
 	bus_write_4(sc->sc_memr, UDMA_CONFIG_REG, sc->udmaconf[atadev->unit]);
 	bus_write_4(sc->sc_memr, PIO_CONFIG_REG, 
 	    sc->wdmaconf[atadev->unit] | sc->pioconf[atadev->unit]);
Index: ata_macio.c
===================================================================
--- ata_macio.c	(revision 190194)
+++ ata_macio.c	(working copy)
@@ -332,6 +332,9 @@
 	struct ata_device *atadev = device_get_softc(request->dev);
 	struct ata_macio_softc *sc = device_get_softc(request->parent);
 
+	if (request->flags & ATA_R_ATAPI && request->bytecount % 16 != 0)
+		request->flags &= ~ATA_R_DMA;
+
 	bus_write_4(sc->sc_mem, ATA_MACIO_TIMINGREG, 
 	    sc->udmaconf[atadev->unit] | sc->wdmaconf[atadev->unit] 
 	    | sc->pioconf[atadev->unit]);