diff --git a/src/i830_dvo.c b/src/i830_dvo.c
index e6ff6af..ca0d00e 100644
--- a/src/i830_dvo.c
+++ b/src/i830_dvo.c
@@ -260,6 +260,12 @@ i830_dvo_mode_set(xf86OutputPtr output, DisplayModePtr mode,
 
     OUTREG(dpll_reg, INREG(dpll_reg) | DPLL_DVO_HIGH_SPEED);
 
+    /* for i830M, bit 30 must be set to 1 for both DPLL_A and DPLL_B */
+    if (IS_I830(pI830)) {
+	dpll_reg = (pipe == 0) ? DPLL_B : DPLL_A;
+	OUTREG(dpll_reg, INREG(dpll_reg) | DPLL_DVO_HIGH_SPEED);
+    }
+
     /*OUTREG(DVOB_SRCDIM,
       (adjusted_mode->HDisplay << DVO_SRCDIM_HORIZONTAL_SHIFT) |
       (adjusted_mode->VDisplay << DVO_SRCDIM_VERTICAL_SHIFT));*/