diff --git a/hw/arm/prusa/parts/software_pwm.c b/hw/arm/prusa/parts/software_pwm.c
index e087d82f96..d39d81e317 100644
--- a/hw/arm/prusa/parts/software_pwm.c
+++ b/hw/arm/prusa/parts/software_pwm.c
@@ -25,6 +25,8 @@
 #include "qemu/osdep.h"
 #include "qemu/module.h"
 #include "migration/vmstate.h"
+#include "qemu/timer.h"
+#include "hw/qdev-properties.h"
 #include "hw/sysbus.h"
 #include "hw/irq.h"
 
@@ -43,7 +45,7 @@ typedef struct SoftwarePWMState {
 	uint8_t clock_count;
 	uint8_t last_pwm[LINE_COUNT];
 	uint16_t line_state;
-
+    bool is_inverted;
 	qemu_irq pwm[LINE_COUNT];
 
 } SoftwarePWMState;
@@ -73,7 +75,7 @@ static void software_pwm_tick(void *opaque, int n, int level)
 			if (s->last_pwm[i] != s->state_count[i])
 			{
 				// printf("Software PWM %d: current %u\n",i,  s->state_count[i]);
-				qemu_set_irq(s->pwm[i], s->state_count[i]);
+				qemu_set_irq(s->pwm[i], s->is_inverted?(255U - s->state_count[i]) : s->state_count[i]);
 			}
 			s->last_pwm[i] = s->state_count[i];
 			s->state_count[i] = 0;
@@ -127,12 +129,18 @@ static void software_pwm_init(Object *obj)
 	qdev_init_gpio_out(dev, s->pwm, LINE_COUNT);
 }
 
-static void softwar_pwm_class_init(ObjectClass *klass, void *data)
+static Property software_pwm_properties[] = {
+    DEFINE_PROP_BOOL("is_inverted", SoftwarePWMState, is_inverted, false),
+    DEFINE_PROP_END_OF_LIST(),
+};
+
+static void software_pwm_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);
 
     dc->reset = software_pwm_reset;
     dc->vmsd = &vmstate_software_pwm;
+    device_class_set_props(dc, software_pwm_properties);
 }
 
 static const TypeInfo SOFTWARE_PWM_info = {
@@ -140,7 +148,7 @@ static const TypeInfo SOFTWARE_PWM_info = {
     .parent        = TYPE_SYS_BUS_DEVICE,
     .instance_size = sizeof(SoftwarePWMState),
     .instance_init = software_pwm_init,
-    .class_init    = softwar_pwm_class_init,
+    .class_init    = software_pwm_class_init,
 };
 
 static void software_pwm_register_types(void)
diff --git a/hw/arm/prusa/prusa-mk4.c b/hw/arm/prusa/prusa-mk4.c
index 3549c84233..f526d919ce 100644
--- a/hw/arm/prusa/prusa-mk4.c
+++ b/hw/arm/prusa/prusa-mk4.c
@@ -511,7 +511,7 @@ static void mk4_init(MachineState *machine)
 
     {
 
-        int32_t ends[4] = { 100*16*253, 100*16*214, 400*16*(cfg.has_loadcell ? 221: 212),0 };
+        int32_t ends[4] = { 100*16*255, 100*16*214, 400*16*(cfg.has_loadcell ? 221: 212),0 };
         static int32_t stepsize[4] = { 100*16, 100*16, 400*16, 320*16 };
  		static const char* links[4] = {"motor[0]","motor[1]","motor[2]","motor[3]"};
         if (cfg.is_400step) {
@@ -740,11 +740,12 @@ static void mk4_init(MachineState *machine)
 
     // hotend = fan1
     // print fan = fan0
-    uint16_t fan_max_rpms[] = { 6600, 8000 };
+    uint16_t fan_max_rpms[] = { 6600, 7000 };
     uint8_t  fan_pwm_pins[] = { 11, 9};
     uint8_t fan_tach_pins[] = { 10, 14};
     uint8_t fan_labels[] = {'P','E'};
 	DeviceState* fanpwm = qdev_new("software-pwm");
+    qdev_prop_set_bit(fanpwm, "is_inverted", true);
 	sysbus_realize_and_unref(SYS_BUS_DEVICE(fanpwm),&error_fatal);
 	qdev_connect_gpio_out_named(stm32_soc_get_periph(dev_soc, STM32_P_TIM14), "timer", 0, qdev_get_gpio_in_named(fanpwm, "tick-in", 0));
     for (int i=0; i<2; i++)
@@ -755,7 +756,7 @@ static void mk4_init(MachineState *machine)
         dev = qdev_new("fan");
         qdev_prop_set_uint8(dev,"label",fan_labels[i]);
         qdev_prop_set_uint32(dev, "max_rpm",fan_max_rpms[i]);
-        qdev_prop_set_bit(dev, "is_nonlinear", i); // E is nonlinear.
+        //qdev_prop_set_bit(dev, "is_nonlinear", i); // E is nonlinear.
         sysbus_realize(SYS_BUS_DEVICE(dev), &error_fatal);
         qdev_connect_gpio_out_named(dev, "tach-out",0,qdev_get_gpio_in(stm32_soc_get_periph(dev_soc, STM32_P_GPIOE),fan_tach_pins[i]));
 		qemu_irq split_fan = qemu_irq_split( qdev_get_gpio_in_named(dev, "pwm-in",0), qdev_get_gpio_in_named(db2, "fan-pwm",i));