diff --git a/share/man/man4/snd_hdspe.4 b/share/man/man4/snd_hdspe.4
--- a/share/man/man4/snd_hdspe.4
+++ b/share/man/man4/snd_hdspe.4
@@ -22,7 +22,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd January 29, 2024
+.Dd February 9, 2024
 .Dt SND_HDSPE 4
 .Os
 .Sh NAME
@@ -64,8 +64,29 @@
 .Xr pcm 4
 device corresponds to a physical port on the sound card.
 For ADAT ports, 8 channel, 4 channel and 2 channel formats are supported.
+The effective number of ADAT channels is 8 channels at single speed
+(32kHz-48kHz), 4 channels at double speed (64kHz-96kHz), and 2 channels at
+quad speed (128kHz-192kHz).
 Depending on sample rate and channel format selected, not all pcm channels can
 be mapped to ADAT channels and vice versa.
+.Sh LOADER TUNABLES
+These settings can be entered at the
+.Xr loader 8
+prompt or in
+.Xr loader.conf 5 .
+.Bl -tag -width indent
+.It Va hw.hdspe.unified_pcm
+If set to 1, all physical ports are combined into one unified pcm device.
+When opened in multi-channel audio software, this makes all ports available
+at the same time, and fully synchronized.
+For resulting channel numbers consult the following table:
+.El
+.Bl -column "HDSPe RayDAT" "Single Speed" "Double Speed" "Quad Speed"
+.Sy "Sound Card" Ta Sy "Single Speed" Ta Sy "Double Speed" Ta Sy "Quad Speed"
+.It "" Ta "Play | Rec" Ta "Play | Rec" Ta "Play | Rec"
+.It HDSPe AIO Ta " 16  |  14" Ta " 12  |  10" Ta " 10  |   8"
+.It HDSPe RayDAT Ta " 36  |  36" Ta " 20  |  20" Ta " 12  |  12"
+.El
 .Sh SYSCTL TUNABLES
 These settings and informational values can be accessed at runtime with the
 .Xr sysctl 8
diff --git a/sys/dev/sound/pci/hdspe-pcm.c b/sys/dev/sound/pci/hdspe-pcm.c
--- a/sys/dev/sound/pci/hdspe-pcm.c
+++ b/sys/dev/sound/pci/hdspe-pcm.c
@@ -41,6 +41,8 @@
 
 #include <mixer_if.h>
 
+#define HDSPE_MATRIX_MAX	8
+
 struct hdspe_latency {
 	uint32_t n;
 	uint32_t period;
@@ -1007,6 +1009,7 @@
 	char status[SND_STATUSLEN];
 	struct sc_pcminfo *scp;
 	const char *buf;
+	uint32_t pcm_flags;
 	int err;
 	int play, rec;
 
@@ -1025,7 +1028,11 @@
 	 * We don't register interrupt handler with snd_setup_intr
 	 * in pcm device. Mark pcm device as MPSAFE manually.
 	 */
-	pcm_setflags(dev, pcm_getflags(dev) | SD_F_MPSAFE);
+	pcm_flags = pcm_getflags(dev) | SD_F_MPSAFE;
+	if (hdspe_channel_count(scp->hc->ports, 8) > HDSPE_MATRIX_MAX)
+		/* Disable vchan conversion, too many channels. */
+		pcm_flags |= SD_F_BITPERFECT;
+	pcm_setflags(dev, pcm_flags);
 
 	play = (hdspe_channel_play_ports(scp->hc)) ? 1 : 0;
 	rec = (hdspe_channel_rec_ports(scp->hc)) ? 1 : 0;
diff --git a/sys/dev/sound/pci/hdspe.c b/sys/dev/sound/pci/hdspe.c
--- a/sys/dev/sound/pci/hdspe.c
+++ b/sys/dev/sound/pci/hdspe.c
@@ -44,6 +44,14 @@
 
 #include <mixer_if.h>
 
+static bool hdspe_unified_pcm = false;
+
+static SYSCTL_NODE(_hw, OID_AUTO, hdspe, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
+    "PCI HDSPe");
+
+SYSCTL_BOOL(_hw_hdspe, OID_AUTO, unified_pcm, CTLFLAG_RWTUN,
+    &hdspe_unified_pcm, 0, "Combine physical ports in one unified pcm device");
+
 static struct hdspe_clock_source hdspe_clock_source_table_rd[] = {
 	{ "internal", 0 << 1 | 1, HDSPE_STATUS1_CLOCK(15),       0,       0 },
 	{ "word",     0 << 1 | 0, HDSPE_STATUS1_CLOCK( 0), 1 << 24, 1 << 25 },
@@ -78,6 +86,11 @@
 	{ 0,                        NULL },
 };
 
+static struct hdspe_channel chan_map_aio_uni[] = {
+	{ HDSPE_CHAN_AIO_ALL, "all" },
+	{ 0,                   NULL },
+};
+
 static struct hdspe_channel chan_map_rd[] = {
 	{ HDSPE_CHAN_RAY_AES,      "aes" },
 	{ HDSPE_CHAN_RAY_SPDIF, "s/pdif" },
@@ -88,6 +101,11 @@
 	{ 0,                        NULL },
 };
 
+static struct hdspe_channel chan_map_rd_uni[] = {
+	{ HDSPE_CHAN_RAY_ALL, "all" },
+	{ 0,                   NULL },
+};
+
 static void
 hdspe_intr(void *p)
 {
@@ -538,11 +556,11 @@
 	switch (rev) {
 	case PCI_REVISION_AIO:
 		sc->type = HDSPE_AIO;
-		chan_map = chan_map_aio;
+		chan_map = hdspe_unified_pcm ? chan_map_aio_uni : chan_map_aio;
 		break;
 	case PCI_REVISION_RAYDAT:
 		sc->type = HDSPE_RAYDAT;
-		chan_map = chan_map_rd;
+		chan_map = hdspe_unified_pcm ? chan_map_rd_uni : chan_map_rd;
 		break;
 	default:
 		return (ENXIO);