diff --git a/src/radeon_crtc.c b/src/radeon_crtc.c
index 3899064..5df7b66 100644
--- a/src/radeon_crtc.c
+++ b/src/radeon_crtc.c
@@ -52,6 +52,9 @@
 #include "sarea.h"
 #endif
 
+extern radeon_encoder_ptr
+radeon_get_encoder(xf86OutputPtr output);
+
 extern void atombios_crtc_mode_set(xf86CrtcPtr crtc,
 				   DisplayModePtr mode,
 				   DisplayModePtr adjusted_mode,
@@ -115,6 +118,28 @@ static Bool
 radeon_crtc_mode_fixup(xf86CrtcPtr crtc, DisplayModePtr mode,
 		     DisplayModePtr adjusted_mode)
 {
+    RADEONCrtcPrivatePtr radeon_crtc = crtc->driver_private;
+    xf86CrtcConfigPtr config = XF86_CRTC_CONFIG_PTR (crtc->scrn);
+    int i, j;
+
+    if (radeon_crtc->crtc_id == 0)
+	return TRUE;
+
+    for (i = 0; i < config->num_output; i++) {
+	if (crtc == config->output[i]->crtc) {
+	    radeon_encoder_ptr radeon_encoder = radeon_get_encoder(config->output[i]);
+	    for (j = 0; j < config->num_output; j++) {
+		if (crtc != config->output[j]->crtc) {
+		    radeon_encoder_ptr other_radeon_encoder = radeon_get_encoder(config->output[j]);
+		    if (radeon_encoder == other_radeon_encoder) {
+			ErrorF("encoder already driven by other crtc\n");
+			return FALSE;
+		    }
+		}
+	    }
+	}
+    }
+
     return TRUE;
 }
 
diff --git a/src/radeon_output.c b/src/radeon_output.c
index 9d9a16c..e5344eb 100644
--- a/src/radeon_output.c
+++ b/src/radeon_output.c
@@ -420,6 +420,26 @@ radeon_dpms(xf86OutputPtr output, int mode)
     if ((mode == DPMSModeOn) && radeon_output->enabled)
 	return;
 
+    if (mode != DPMSModeOn) {
+	radeon_encoder_ptr radeon_encoder = radeon_get_encoder(output);
+	xf86CrtcConfigPtr config = XF86_CRTC_CONFIG_PTR (output->scrn);
+	int i;
+
+	for (i = 0; i < config->num_output; i++) {
+	    if (output != config->output[i]) {
+		radeon_encoder_ptr other_radeon_encoder =
+		    radeon_get_encoder(config->output[i]);
+		if (radeon_encoder == other_radeon_encoder) {
+		    xf86CrtcPtr crtc = output->crtc;
+		    if (crtc == NULL)
+			return;
+		    else if (!crtc->enabled)
+			return;
+		}
+	    }
+	}
+    }
+
     if (IS_AVIVO_VARIANT || info->r4xx_atom) {
 	atombios_output_dpms(output, mode);
     } else {