diff --git a/drivers/ide/ide.c b/drivers/ide/ide.c
index 8eb7f83..3d1fc5f 100644
--- a/drivers/ide/ide.c
+++ b/drivers/ide/ide.c
@@ -1116,6 +1116,18 @@
 	put_device(&hwif->gendev);
 }
 
+int ide_vlb_clk;
+EXPORT_SYMBOL_GPL(ide_vlb_clk);
+
+module_param_named(vlb_clock, ide_vlb_clk, int, 0);
+MODULE_PARM_DESC(vlb_clock, "VLB clock frequency (in MHz)");
+
+int ide_pci_clk;
+EXPORT_SYMBOL_GPL(ide_pci_clk);
+
+module_param_named(pci_clock, ide_pci_clk, int, 0);
+MODULE_PARM_DESC(pci_clock, "PCI bus clock frequency (in MHz)");
+
 static unsigned int ide_ignore_cable;
 
 static int ide_set_ignore_cable(const char *s, struct kernel_param *kp)
diff --git a/drivers/ide/legacy/ali14xx.c b/drivers/ide/legacy/ali14xx.c
index c689863..d2756c9 100644
--- a/drivers/ide/legacy/ali14xx.c
+++ b/drivers/ide/legacy/ali14xx.c
@@ -116,7 +116,7 @@
 	int time1, time2;
 	u8 param1, param2, param3, param4;
 	unsigned long flags;
-	int bus_speed = system_bus_clock();
+	int bus_speed = ide_vlb_clk ? ide_vlb_clk : system_bus_clock();
 
 	/* calculate timing, according to PIO mode */
 	time1 = ide_pio_cycle_time(drive, pio);
diff --git a/drivers/ide/legacy/ht6560b.c b/drivers/ide/legacy/ht6560b.c
index 8b2a5b4..d626c76 100644
--- a/drivers/ide/legacy/ht6560b.c
+++ b/drivers/ide/legacy/ht6560b.c
@@ -212,8 +212,8 @@
 {
 	int active_time, recovery_time;
 	int active_cycles, recovery_cycles;
-	int bus_speed = system_bus_clock();
-	
+	int bus_speed = ide_vlb_clk ? ide_vlb_clk : system_bus_clock();
+
         if (pio) {
 		unsigned int cycle_time;
 
diff --git a/drivers/ide/legacy/qd65xx.c b/drivers/ide/legacy/qd65xx.c
index 61d5889..5621963 100644
--- a/drivers/ide/legacy/qd65xx.c
+++ b/drivers/ide/legacy/qd65xx.c
@@ -114,17 +114,18 @@
 
 static u8 qd6500_compute_timing (ide_hwif_t *hwif, int active_time, int recovery_time)
 {
-	u8 active_cycle,recovery_cycle;
+	int clk = ide_vlb_clk ? ide_vlb_clk : system_bus_clock();
+	u8 act_cyc, rec_cyc;
 
-	if (system_bus_clock()<=33) {
-		active_cycle =   9  - IDE_IN(active_time   * system_bus_clock() / 1000 + 1, 2, 9);
-		recovery_cycle = 15 - IDE_IN(recovery_time * system_bus_clock() / 1000 + 1, 0, 15);
+	if (clk <= 33) {
+		act_cyc =  9 - IDE_IN(active_time   * clk / 1000 + 1, 2,  9);
+		rec_cyc = 15 - IDE_IN(recovery_time * clk / 1000 + 1, 0, 15);
 	} else {
-		active_cycle =   8  - IDE_IN(active_time   * system_bus_clock() / 1000 + 1, 1, 8);
-		recovery_cycle = 18 - IDE_IN(recovery_time * system_bus_clock() / 1000 + 1, 3, 18);
+		act_cyc =  8 - IDE_IN(active_time   * clk / 1000 + 1, 1,  8);
+		rec_cyc = 18 - IDE_IN(recovery_time * clk / 1000 + 1, 3, 18);
 	}
 
-	return((recovery_cycle<<4) | 0x08 | active_cycle);
+	return (rec_cyc << 4) | 0x08 | act_cyc;
 }
 
 /*
@@ -135,10 +136,13 @@
 
 static u8 qd6580_compute_timing (int active_time, int recovery_time)
 {
-	u8 active_cycle   = 17 - IDE_IN(active_time   * system_bus_clock() / 1000 + 1, 2, 17);
-	u8 recovery_cycle = 15 - IDE_IN(recovery_time * system_bus_clock() / 1000 + 1, 2, 15);
+	int clk = ide_vlb_clk ? ide_vlb_clk : system_bus_clock();
+	u8 act_cyc, rec_cyc;
 
-	return((recovery_cycle<<4) | active_cycle);
+	act_cyc = 17 - IDE_IN(active_time   * clk / 1000 + 1, 2, 17);
+	rec_cyc = 15 - IDE_IN(recovery_time * clk / 1000 + 1, 2, 15);
+
+	return (rec_cyc << 4) | act_cyc;
 }
 
 /*
diff --git a/drivers/ide/pci/aec62xx.c b/drivers/ide/pci/aec62xx.c
index ca16f37..7f46c22 100644
--- a/drivers/ide/pci/aec62xx.c
+++ b/drivers/ide/pci/aec62xx.c
@@ -140,7 +140,7 @@
 
 static unsigned int __devinit init_chipset_aec62xx(struct pci_dev *dev, const char *name)
 {
-	int bus_speed = system_bus_clock();
+	int bus_speed = ide_pci_clk ? ide_pci_clk : system_bus_clock();
 
 	if (bus_speed <= 33)
 		pci_set_drvdata(dev, (void *) aec6xxx_33_base);
diff --git a/drivers/ide/pci/alim15x3.c b/drivers/ide/pci/alim15x3.c
index b5a3bc3..075dcf9 100644
--- a/drivers/ide/pci/alim15x3.c
+++ b/drivers/ide/pci/alim15x3.c
@@ -294,7 +294,7 @@
 	int s_time, a_time, c_time;
 	u8 s_clc, a_clc, r_clc;
 	unsigned long flags;
-	int bus_speed = system_bus_clock();
+	int bus_speed = ide_pci_clk ? ide_pci_clk : system_bus_clock();
 	int port = hwif->channel ? 0x5c : 0x58;
 	int portFIFO = hwif->channel ? 0x55 : 0x54;
 	u8 cd_dma_fifo = 0;
diff --git a/drivers/ide/pci/amd74xx.c b/drivers/ide/pci/amd74xx.c
index f7c8838..efcf543 100644
--- a/drivers/ide/pci/amd74xx.c
+++ b/drivers/ide/pci/amd74xx.c
@@ -179,7 +179,7 @@
  * Determine the system bus clock.
  */
 
-	amd_clock = system_bus_clock() * 1000;
+	amd_clock = (ide_pci_clk ? ide_pci_clk : system_bus_clock()) * 1000;
 
 	switch (amd_clock) {
 		case 33000: amd_clock = 33333; break;
diff --git a/drivers/ide/pci/cmd640.c b/drivers/ide/pci/cmd640.c
index 0f6f11e6..6e7a6fa 100644
--- a/drivers/ide/pci/cmd640.c
+++ b/drivers/ide/pci/cmd640.c
@@ -552,7 +552,14 @@
 {
 	int setup_time, active_time, recovery_time, clock_time;
 	u8 setup_count, active_count, recovery_count, recovery_count2, cycle_count;
-	int bus_speed = system_bus_clock();
+	int bus_speed;
+
+	if (cmd640_vlb && ide_vlb_clk)
+		bus_speed = ide_vlb_clk;
+	else if (!cmd640_vlb && ide_pci_clk)
+		bus_speed = ide_pci_clk;
+	else
+		bus_speed = system_bus_clock();
 
 	if (pio_mode > 5)
 		pio_mode = 5;
diff --git a/drivers/ide/pci/cmd64x.c b/drivers/ide/pci/cmd64x.c
index 006fb62..0867471 100644
--- a/drivers/ide/pci/cmd64x.c
+++ b/drivers/ide/pci/cmd64x.c
@@ -68,8 +68,8 @@
  */
 static void program_cycle_times (ide_drive_t *drive, int cycle_time, int active_time)
 {
-	struct pci_dev *dev	= to_pci_dev(drive->hwif->dev);
-	int clock_time		= 1000 / system_bus_clock();
+	struct pci_dev *dev = to_pci_dev(drive->hwif->dev);
+	int clock_time = 1000 / (ide_pci_clk ? ide_pci_clk : system_bus_clock());
 	u8  cycle_count, active_count, recovery_count, drwtim;
 	static const u8 recovery_values[] =
 		{15, 15, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 0};
@@ -128,7 +128,7 @@
 			    ide_pio_timings[pio].active_time);
 
 	setup_count = quantize_timing(ide_pio_timings[pio].setup_time,
-				      1000 / system_bus_clock());
+			1000 / (ide_pci_clk ? ide_pci_clk : system_bus_clock()));
 
 	/*
 	 * The primary channel has individual address setup timing registers
diff --git a/drivers/ide/pci/cy82c693.c b/drivers/ide/pci/cy82c693.c
index e30eae5..8ef551a 100644
--- a/drivers/ide/pci/cy82c693.c
+++ b/drivers/ide/pci/cy82c693.c
@@ -136,7 +136,7 @@
 static void compute_clocks(u8 pio, pio_clocks_t *p_pclk)
 {
 	int clk1, clk2;
-	int bus_speed = system_bus_clock();	/* get speed of PCI bus */
+	int bus_speed = ide_pci_clk ? ide_pci_clk : system_bus_clock();
 
 	/* we don't check against CY82C693's min and max speed,
 	 * so you can play with the idebus=xx parameter
diff --git a/drivers/ide/pci/opti621.c b/drivers/ide/pci/opti621.c
index 9edacba..f766be9 100644
--- a/drivers/ide/pci/opti621.c
+++ b/drivers/ide/pci/opti621.c
@@ -210,7 +210,7 @@
 {
 	if (pio != PIO_NOT_EXIST) {
 		int adr_setup, data_pls;
-		int bus_speed = system_bus_clock();
+		int bus_speed = ide_pci_clk ? ide_pci_clk : system_bus_clock();
 
 		adr_setup = ide_pio_timings[pio].setup_time;
 		data_pls = ide_pio_timings[pio].active_time;
diff --git a/drivers/ide/pci/via82cxxx.c b/drivers/ide/pci/via82cxxx.c
index bbd17be..566e0ec 100644
--- a/drivers/ide/pci/via82cxxx.c
+++ b/drivers/ide/pci/via82cxxx.c
@@ -340,7 +340,7 @@
 	 * Determine system bus clock.
 	 */
 
-	via_clock = system_bus_clock() * 1000;
+	via_clock = (ide_pci_clk ? ide_pci_clk : system_bus_clock()) * 1000;
 
 	switch (via_clock) {
 		case 33000: via_clock = 33333; break;
diff --git a/include/linux/ide.h b/include/linux/ide.h
index 78e5fca..37d00c2 100644
--- a/include/linux/ide.h
+++ b/include/linux/ide.h
@@ -801,6 +801,9 @@
 #endif
 extern int noautodma;
 
+extern int ide_vlb_clk;
+extern int ide_pci_clk;
+
 ide_hwif_t *ide_find_port_slot(const struct ide_port_info *);
 
 static inline ide_hwif_t *ide_find_port(void)