diff --git a/src/northbridge/intel/x4x/early_init.c b/src/northbridge/intel/x4x/early_init.c
index f942d59..e6083d9 100644
--- a/src/northbridge/intel/x4x/early_init.c
+++ b/src/northbridge/intel/x4x/early_init.c
@@ -62,7 +62,7 @@
 	EPBAR8(EPVC0RCTL) = 1;
 	EPBAR8(EPPVCCAP1) = 1;
 
-	switch (MCHBAR32(0xc00) & 0x7) {
+	switch (MCHBAR32(CLKCFG_MCHBAR) & CLKCFG_FSBCLK_MASK) {
 	case 0x0:
 		/* FSB 1066 */
 		EPBAR32(EPVC1ITC) = 0x0001a6db;
diff --git a/src/northbridge/intel/x4x/raminit.c b/src/northbridge/intel/x4x/raminit.c
index 97c0a53..5f937cf 100644
--- a/src/northbridge/intel/x4x/raminit.c
+++ b/src/northbridge/intel/x4x/raminit.c
@@ -412,7 +412,7 @@
 
 static void find_fsb_speed(struct sysinfo *s)
 {
-	switch (MCHBAR32(0xc00) & 0x7) {
+	switch ((MCHBAR32(CLKCFG_MCHBAR) & CLKCFG_FSBCLK_MASK) >> CLKCFG_FSBCLK_SHIFT) {
 	case 0x0:
 		s->max_fsb = FSB_CLOCK_1066MHz;
 		break;
diff --git a/src/northbridge/intel/x4x/raminit_ddr23.c b/src/northbridge/intel/x4x/raminit_ddr23.c
index 84dbff5..6863ef8 100644
--- a/src/northbridge/intel/x4x/raminit_ddr23.c
+++ b/src/northbridge/intel/x4x/raminit_ddr23.c
@@ -1952,11 +1952,12 @@
 			MCHBAR8_OR(0x1a8, 0x4);
 
 		/* Set frequency */
-		MCHBAR32_AND_OR(0xc00, ~0x70,
-			(s->selected_timings.mem_clk << 4) | (1 << 10));
+		MCHBAR32_AND_OR(CLKCFG_MCHBAR, ~CLKCFG_MEMCLK_MASK,
+			(s->selected_timings.mem_clk << CLKCFG_MEMCLK_SHIFT) | CLKCFG_UPDATE);
 
 		/* Overwrite value if chipset rejects it */
-		s->selected_timings.mem_clk = (MCHBAR8(0xc00) & 0x70) >> 4;
+		s->selected_timings.mem_clk =
+			(MCHBAR8(CLKCFG_MCHBAR) & CLKCFG_MEMCLK_MASK) >> CLKCFG_MEMCLK_SHIFT;
 		if (s->selected_timings.mem_clk > (s->max_fsb + 3))
 			die("Error: DDR is faster than FSB, halt\n");
 	}
diff --git a/src/northbridge/intel/x4x/x4x.h b/src/northbridge/intel/x4x/x4x.h
index 0c0e605..991d175 100644
--- a/src/northbridge/intel/x4x/x4x.h
+++ b/src/northbridge/intel/x4x/x4x.h
@@ -74,7 +74,7 @@
 #define CLKCFG_FSBCLK_MASK	(7 << CLKCFG_FSBCLK_SHIFT)
 #define CLKCFG_MEMCLK_SHIFT	4
 #define CLKCFG_MEMCLK_MASK	(7 << CLKCFG_MEMCLK_SHIFT)
-#define CLKCFG_UPDATE		(1 << 12)
+#define CLKCFG_UPDATE		(1 << 10)
 
 #define SSKPD_MCHBAR		0x0c20 /* 64 bit */