Index: sys/dev/mps/mps_sas.c
===================================================================
--- sys/dev/mps/mps_sas.c
+++ sys/dev/mps/mps_sas.c
@@ -928,6 +928,8 @@
 	case XPT_PATH_INQ:
 	{
 		struct ccb_pathinq *cpi = &ccb->cpi;
+		struct mps_softc *sc = sassc->sc;
+		uint8_t sges_per_frame;
 
 		cpi->version_num = 1;
 		cpi->hba_inquiry = PI_SDTR_ABLE|PI_TAG_ABLE|PI_WIDE_16;
@@ -951,12 +953,16 @@
 		cpi->transport_version = 0;
 		cpi->protocol = PROTO_SCSI;
 		cpi->protocol_version = SCSI_REV_SPC;
-#if __FreeBSD_version >= 800001
+
 		/*
-		 * XXX KDM where does this number come from?
-		 */
-		cpi->maxio = 256 * 1024;
-#endif
+		 * Max IO Size is Page Size * the following:
+		 * ((SGEs per frame - 1 for chain element) *
+		 * Max Chain Depth) + 1 for no chain needed in last frame
+		 */
+		sges_per_frame = ((sc->facts->IOCRequestFrameSize * 4) /
+		    sizeof(MPI2_SGE_SIMPLE64)) - 1;
+		cpi->maxio = (sges_per_frame * sc->facts->MaxChainDepth + 1);
+		cpi->maxio *= PAGE_SIZE;
 		mpssas_set_ccbstatus(ccb, CAM_REQ_CMP);
 		break;
 	}