diff --git a/src/i830_display.c b/src/i830_display.c
index f61d3c4..406b8e9 100644
--- a/src/i830_display.c
+++ b/src/i830_display.c
@@ -1086,6 +1086,11 @@ i830_crtc_mode_set(xf86CrtcPtr crtc, DisplayModePtr mode,
 	if (IS_I965G(pI830))
 	    dpll |= (6 << PLL_LOAD_PULSE_PHASE_SHIFT);
     } else {
+	/* for i830M, always set DVO bit to make LVDS work with
+	 * external display */
+	if (IS_I830(pI830))
+	    dpll |= DPLL_DVO_HIGH_SPEED;
+
 	if (is_lvds) {
 	    dpll |= (1 << (clock.p1 - 1)) << DPLL_FPA01_P1_POST_DIV_SHIFT;
 	} else {