diff --git a/flight/PiOS/Boards/STM32F4xx_Revolution.h b/flight/PiOS/Boards/STM32F4xx_Revolution.h
index 061b0fce0..f8cacf260 100644
--- a/flight/PiOS/Boards/STM32F4xx_Revolution.h
+++ b/flight/PiOS/Boards/STM32F4xx_Revolution.h
@@ -135,9 +135,38 @@ extern uint32_t pios_com_telem_usb_id;
 
 //-------------------------
 // System Settings
+// 
+// See also System_stm32f4xx.c
 //-------------------------
-#define PIOS_MASTER_CLOCK                       168000000
-#define PIOS_PERIPHERAL_CLOCK                   (PIOS_MASTER_CLOCK / 2)
+//These macros are deprecated
+//please use PIOS_PERIPHERAL_APBx_CLOCK According to the table below
+//#define PIOS_MASTER_CLOCK                       
+//#define PIOS_PERIPHERAL_CLOCK                   
+//#define PIOS_PERIPHERAL_CLOCK							
+
+#define PIOS_SYSCLK										168000000
+//	Peripherals that belongs to APB1 are:
+//	DAC			|PWR				|CAN1,2
+//	I2C1,2,3		|UART4,5			|USART3,2
+//	I2S3Ext		|SPI3/I2S3		|SPI2/I2S2
+//	I2S2Ext		|IWDG				|WWDG
+//	RTC/BKP reg	
+// TIM2,3,4,5,6,7,12,13,14
+
+// Calculated as SYSCLK / APBPresc * (APBPre == 1 ? 1 : 2)   
+// Default APB1 Prescaler = 4 
+#define PIOS_PERIPHERAL_APB1_CLOCK					(PIOS_SYSCLK / 2)
+
+//	Peripherals belonging to APB2
+//	SDIO			|EXTI				|SYSCFG			|SPI1
+//	ADC1,2,3				
+//	USART1,6
+//	TIM1,8,9,10,11
+//
+// Default APB2 Prescaler = 2
+//
+#define PIOS_PERIPHERAL_APB2_CLOCK					PIOS_SYSCLK
+
 
 //-------------------------
 // Interrupt Priorities
diff --git a/flight/PiOS/STM32F4xx/pios_servo.c b/flight/PiOS/STM32F4xx/pios_servo.c
index 876911126..cfcf5c1e5 100644
--- a/flight/PiOS/STM32F4xx/pios_servo.c
+++ b/flight/PiOS/STM32F4xx/pios_servo.c
@@ -96,7 +96,7 @@ void PIOS_Servo_SetHz(uint16_t * speeds, uint8_t banks)
 	TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure = servo_cfg->tim_base_init;
 	TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
 	TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
-	TIM_TimeBaseStructure.TIM_Prescaler = (PIOS_MASTER_CLOCK / 1000000) - 1;
+	//
 
 	uint8_t set = 0;
 
@@ -109,6 +109,14 @@ void PIOS_Servo_SetHz(uint16_t * speeds, uint8_t banks)
 			new &= chan->timer != servo_cfg->channels[j].timer;
 
 		if(new) {
+			// Choose the correct prescaler value for the APB the timer is attached
+			if (chan->timer==TIM1 || chan->timer==TIM8 || chan->timer==TIM9 || chan->timer==TIM10 || chan->timer==TIM11 ){
+				TIM_TimeBaseStructure.TIM_Prescaler = (PIOS_PERIPHERAL_APB2_CLOCK / 1000000) - 1;
+			}
+			else {
+				TIM_TimeBaseStructure.TIM_Prescaler = (PIOS_PERIPHERAL_APB1_CLOCK / 1000000) - 1;
+			}
+
 			TIM_TimeBaseStructure.TIM_Period = ((1000000 / speeds[set]) - 1);
 			TIM_TimeBaseInit(chan->timer, &TIM_TimeBaseStructure);
 			set++;
diff --git a/flight/board_hw_defs/revolution/board_hw_defs.c b/flight/board_hw_defs/revolution/board_hw_defs.c
index 1cf70fc31..dff3bfc76 100644
--- a/flight/board_hw_defs/revolution/board_hw_defs.c
+++ b/flight/board_hw_defs/revolution/board_hw_defs.c
@@ -974,8 +974,15 @@ void PIOS_RTC_IRQ_Handler (void)
 
 #include "pios_tim_priv.h"
 
-static const TIM_TimeBaseInitTypeDef tim_3_5_9_10_11_time_base = {
-	.TIM_Prescaler = (PIOS_MASTER_CLOCK / 1000000) - 1,
+static const TIM_TimeBaseInitTypeDef tim_3_5_time_base = {
+	.TIM_Prescaler = (PIOS_PERIPHERAL_APB1_CLOCK / 1000000) - 1,
+	.TIM_ClockDivision = TIM_CKD_DIV1,
+	.TIM_CounterMode = TIM_CounterMode_Up,
+	.TIM_Period = ((1000000 / PIOS_SERVO_UPDATE_HZ) - 1),
+	.TIM_RepetitionCounter = 0x0000,
+};
+static const TIM_TimeBaseInitTypeDef tim_9_10_11_time_base = {
+	.TIM_Prescaler = (PIOS_PERIPHERAL_APB2_CLOCK / 1000000) - 1,
 	.TIM_ClockDivision = TIM_CKD_DIV1,
 	.TIM_CounterMode = TIM_CounterMode_Up,
 	.TIM_Period = ((1000000 / PIOS_SERVO_UPDATE_HZ) - 1),
@@ -984,7 +991,7 @@ static const TIM_TimeBaseInitTypeDef tim_3_5_9_10_11_time_base = {
 
 static const struct pios_tim_clock_cfg tim_3_cfg = {
 	.timer = TIM3,
-	.time_base_init = &tim_3_5_9_10_11_time_base,
+	.time_base_init = &tim_3_5_time_base,
 	.irq = {
 		.init = {
 			.NVIC_IRQChannel                   = TIM3_IRQn,
@@ -997,7 +1004,7 @@ static const struct pios_tim_clock_cfg tim_3_cfg = {
 
 static const struct pios_tim_clock_cfg tim_5_cfg = {
 	.timer = TIM5,
-	.time_base_init = &tim_3_5_9_10_11_time_base,
+	.time_base_init = &tim_3_5_time_base,
 	.irq = {
 		.init = {
 			.NVIC_IRQChannel                   = TIM5_IRQn,
@@ -1010,7 +1017,7 @@ static const struct pios_tim_clock_cfg tim_5_cfg = {
 
 static const struct pios_tim_clock_cfg tim_9_cfg = {
 	.timer = TIM9,
-	.time_base_init = &tim_3_5_9_10_11_time_base,
+	.time_base_init = &tim_9_10_11_time_base,
 	.irq = {
 		.init = {
 			.NVIC_IRQChannel                   = TIM1_BRK_TIM9_IRQn,
@@ -1023,7 +1030,7 @@ static const struct pios_tim_clock_cfg tim_9_cfg = {
 
 static const struct pios_tim_clock_cfg tim_10_cfg = {
 	.timer = TIM10,
-	.time_base_init = &tim_3_5_9_10_11_time_base,
+	.time_base_init = &tim_9_10_11_time_base,
 	.irq = {
 		.init = {
 			.NVIC_IRQChannel                   = TIM1_UP_TIM10_IRQn,
@@ -1036,7 +1043,7 @@ static const struct pios_tim_clock_cfg tim_10_cfg = {
 
 static const struct pios_tim_clock_cfg tim_11_cfg = {
 	.timer = TIM11,
-	.time_base_init = &tim_3_5_9_10_11_time_base,
+	.time_base_init = &tim_9_10_11_time_base,
 	.irq = {
 		.init = {
 			.NVIC_IRQChannel                   = TIM1_TRG_COM_TIM11_IRQn,
@@ -1047,9 +1054,17 @@ static const struct pios_tim_clock_cfg tim_11_cfg = {
 	},
 };
 
-// Set up timers that only have inputs
-static const TIM_TimeBaseInitTypeDef tim_1_4_time_base = {
-	.TIM_Prescaler = (PIOS_MASTER_CLOCK / 1000000) - 1,
+// Set up timers that only have inputs on APB2
+static const TIM_TimeBaseInitTypeDef tim_1_time_base = {
+	.TIM_Prescaler = (PIOS_PERIPHERAL_APB2_CLOCK / 1000000) - 1,
+	.TIM_ClockDivision = TIM_CKD_DIV1,
+	.TIM_CounterMode = TIM_CounterMode_Up,
+	.TIM_Period = 0xFFFF,
+	.TIM_RepetitionCounter = 0x0000,
+};
+// Set up timers that only have inputs on APB2
+static const TIM_TimeBaseInitTypeDef tim_4_time_base = {
+	.TIM_Prescaler = (PIOS_PERIPHERAL_APB1_CLOCK / 1000000) - 1,
 	.TIM_ClockDivision = TIM_CKD_DIV1,
 	.TIM_CounterMode = TIM_CounterMode_Up,
 	.TIM_Period = 0xFFFF,
@@ -1058,7 +1073,7 @@ static const TIM_TimeBaseInitTypeDef tim_1_4_time_base = {
 
 static const struct pios_tim_clock_cfg tim_1_cfg = {
 	.timer = TIM1,
-	.time_base_init = &tim_1_4_time_base,
+	.time_base_init = &tim_1_time_base,
 	.irq = {
 		.init = {
 			.NVIC_IRQChannel                   = TIM1_CC_IRQn,
@@ -1071,7 +1086,7 @@ static const struct pios_tim_clock_cfg tim_1_cfg = {
 
 static const struct pios_tim_clock_cfg tim_4_cfg = {
 	.timer = TIM4,
-	.time_base_init = &tim_1_4_time_base,
+	.time_base_init = &tim_4_time_base,
 	.irq = {
 		.init = {
 			.NVIC_IRQChannel                   = TIM4_IRQn,