diff --git a/src/chipset/intel_420ex.c b/src/chipset/intel_420ex.c
index 03720b668..4d810f65b 100644
--- a/src/chipset/intel_420ex.c
+++ b/src/chipset/intel_420ex.c
@@ -522,7 +522,7 @@ i420ex_speed_changed(void *priv)
     if (te)
         timer_set_delay_u64(&dev->timer, ((uint64_t) dev->timer_latch) * TIMER_USEC);
 
-    te = timer_is_enabled(&dev->fast_off_timer);
+    te = timer_is_on(&dev->fast_off_timer);
 
     timer_stop(&dev->fast_off_timer);
     if (te)
diff --git a/src/chipset/intel_piix.c b/src/chipset/intel_piix.c
index add421b96..4066abe31 100644
--- a/src/chipset/intel_piix.c
+++ b/src/chipset/intel_piix.c
@@ -1541,10 +1541,10 @@ piix_speed_changed(void *priv)
     if (!dev)
         return;
 
-    int te = timer_is_enabled(&dev->fast_off_timer);
+    int to = timer_is_on(&dev->fast_off_timer);
 
     timer_stop(&dev->fast_off_timer);
-    if (te)
+    if (to)
         timer_on_auto(&dev->fast_off_timer, ((double) cpu_fast_off_val + 1) * dev->fast_off_period);
 }
 
diff --git a/src/chipset/intel_sio.c b/src/chipset/intel_sio.c
index 0f32eb4c8..03a292da8 100644
--- a/src/chipset/intel_sio.c
+++ b/src/chipset/intel_sio.c
@@ -497,7 +497,7 @@ sio_speed_changed(void *priv)
         timer_set_delay_u64(&dev->timer, ((uint64_t) dev->timer_latch) * TIMER_USEC);
 
     if (dev->id == 0x03) {
-        te = timer_is_enabled(&dev->fast_off_timer);
+        te = timer_is_on(&dev->fast_off_timer);
 
         timer_stop(&dev->fast_off_timer);
         if (te)
diff --git a/src/cpu/386.c b/src/cpu/386.c
index fb42a222f..20b67ff89 100644
--- a/src/cpu/386.c
+++ b/src/cpu/386.c
@@ -369,7 +369,7 @@ exec386_2386(int cycs)
             }
 
             if (TIMER_VAL_LESS_THAN_VAL(timer_target, (uint32_t) tsc))
-                timer_process_inline();
+                timer_process();
 
 #ifdef USE_GDBSTUB
             if (gdbstub_instruction())
diff --git a/src/cpu/386_dynarec.c b/src/cpu/386_dynarec.c
index a31704c1b..ab01d28b8 100644
--- a/src/cpu/386_dynarec.c
+++ b/src/cpu/386_dynarec.c
@@ -256,7 +256,7 @@ update_tsc(void)
 
     if (cycdiff > 0) {
         if (TIMER_VAL_LESS_THAN_VAL(timer_target, (uint32_t) tsc))
-            timer_process_inline();
+            timer_process();
     }
 }
 
@@ -782,7 +782,7 @@ exec386_dynarec(int cycs)
 
             if (cycdiff > 0) {
                 if (TIMER_VAL_LESS_THAN_VAL(timer_target, (uint32_t) tsc))
-                    timer_process_inline();
+                    timer_process();
             }
 
 #    ifdef USE_GDBSTUB
@@ -943,7 +943,7 @@ exec386(int cycs)
             }
 
             if (TIMER_VAL_LESS_THAN_VAL(timer_target, (uint32_t) tsc))
-                timer_process_inline();
+                timer_process();
 
 #ifdef USE_GDBSTUB
             if (gdbstub_instruction())
diff --git a/src/device/serial.c b/src/device/serial.c
index 5dd5d8420..da34fd212 100644
--- a/src/device/serial.c
+++ b/src/device/serial.c
@@ -363,7 +363,7 @@ serial_update_speed(serial_t *dev)
     if (dev->transmit_enabled & 3)
         timer_on_auto(&dev->transmit_timer, dev->transmit_period);
 
-    if (timer_is_enabled(&dev->timeout_timer))
+    if (timer_is_on(&dev->timeout_timer))
         timer_on_auto(&dev->timeout_timer, 4.0 * dev->bits * dev->transmit_period);
 }
 
diff --git a/src/include/86box/timer.h b/src/include/86box/timer.h
index 586e3d2fe..45b648151 100644
--- a/src/include/86box/timer.h
+++ b/src/include/86box/timer.h
@@ -122,7 +122,7 @@ timer_is_enabled(pc_timer_t *timer)
 static __inline int
 timer_is_on(pc_timer_t *timer)
 {
-    return ((timer->flags & TIMER_ENABLED) && (timer->period > 0.0));
+    return ((timer->flags & TIMER_SPLIT) && (timer->flags & TIMER_ENABLED));
 }
 
 /*Return integer timestamp of timer*/
@@ -184,45 +184,8 @@ timer_set_p(pc_timer_t *timer, void *priv)
 
 /* The API for big timer periods starts here. */
 extern void timer_stop(pc_timer_t *timer);
-extern void timer_advance_ex(pc_timer_t *timer, int start);
-extern void timer_on(pc_timer_t *timer, double period, int start);
 extern void timer_on_auto(pc_timer_t *timer, double period);
 
-extern void timer_remove_head(void);
-
-extern pc_timer_t *timer_head;
-extern int         timer_inited;
-
-static __inline void
-timer_process_inline(void)
-{
-    pc_timer_t *timer;
-
-    if (!timer_head)
-        return;
-
-    while (1) {
-        timer = timer_head;
-
-        if (!TIMER_LESS_THAN_VAL(timer, (uint32_t) tsc))
-            break;
-
-        timer_head = timer->next;
-        if (timer_head)
-            timer_head->prev = NULL;
-
-        timer->next = timer->prev = NULL;
-        timer->flags &= ~TIMER_ENABLED;
-
-        if (timer->flags & TIMER_SPLIT)
-            timer_advance_ex(timer, 0);   /* We're splitting a > 1 s period into multiple <= 1 s periods. */
-        else if (timer->callback != NULL) /* Make sure it's no NULL, so that we can have a NULL callback when no operation is needed. */
-            timer->callback(timer->priv);
-    }
-
-    timer_target = timer_head->ts.ts32.integer;
-}
-
 #ifdef __cplusplus
 }
 #endif
diff --git a/src/scsi/scsi_ncr5380.c b/src/scsi/scsi_ncr5380.c
index 8b0ae3c0c..c4bec884d 100644
--- a/src/scsi/scsi_ncr5380.c
+++ b/src/scsi/scsi_ncr5380.c
@@ -639,7 +639,8 @@ ncr_write(uint16_t port, uint8_t val, void *priv)
                 }
             } else {
                 /*Don't stop the timer until it finishes the transfer*/
-                if (ncr_dev->block_count_loaded && (ncr->mode & MODE_DMA) && !timer_is_enabled(&ncr_dev->timer)) {
+                if (ncr_dev->block_count_loaded && (ncr->mode & MODE_DMA) &&
+                    !timer_is_on(&ncr_dev->timer)) {
                     ncr_log("Continuing DMA mode\n");
                     ncr_timer_on(ncr_dev, ncr, 0);
                 }
@@ -671,7 +672,7 @@ ncr_write(uint16_t port, uint8_t val, void *priv)
                 if (dev->buffer_length > 0) {
                     memset(ncr_dev->t128.buffer, 0, MIN(512, dev->buffer_length));
 
-                    ncr_log("DMA send timer start, enabled? = %i\n", timer_is_enabled(&ncr_dev->timer));
+                    ncr_log("DMA send timer start, enabled? = %i\n", timer_is_on(&ncr_dev->timer));
                     ncr_dev->t128.block_count  = dev->buffer_length >> 9;
                     ncr_dev->t128.block_loaded = 1;
 
@@ -679,7 +680,7 @@ ncr_write(uint16_t port, uint8_t val, void *priv)
                     ncr_dev->t128.status |= 0x04;
                 }
             } else {
-                if ((ncr->mode & MODE_DMA) && !timer_is_enabled(&ncr_dev->timer)) {
+                if ((ncr->mode & MODE_DMA) && !timer_is_on(&ncr_dev->timer)) {
                     memset(ncr_dev->buffer, 0, MIN(128, dev->buffer_length));
 
                     ncr_log("DMA send timer on\n");
@@ -693,7 +694,8 @@ ncr_write(uint16_t port, uint8_t val, void *priv)
             /*a Read 6/10 has occurred, start the timer when the block count is loaded*/
             ncr->dma_mode = DMA_INITIATOR_RECEIVE;
             if (ncr_dev->type == 3) {
-                ncr_log("DMA receive timer start, enabled? = %i, cdb[0] = %02x, buflen = %i\n", timer_is_enabled(&ncr_dev->timer), ncr->command[0], dev->buffer_length);
+                ncr_log("DMA receive timer start, enabled? = %i, cdb[0] = %02x, buflen = %i\n",
+                        timer_is_on(&ncr_dev->timer), ncr->command[0], dev->buffer_length);
                 if (dev->buffer_length > 0) {
                     memset(ncr_dev->t128.buffer, 0, MIN(512, dev->buffer_length));
 
@@ -709,7 +711,7 @@ ncr_write(uint16_t port, uint8_t val, void *priv)
                     timer_on_auto(&ncr_dev->timer, 0.02);
                 }
             } else {
-                if ((ncr->mode & MODE_DMA) && !timer_is_enabled(&ncr_dev->timer)) {
+                if ((ncr->mode & MODE_DMA) && !timer_is_on(&ncr_dev->timer)) {
                     memset(ncr_dev->buffer, 0, MIN(128, dev->buffer_length));
 
                     ncr_log("DMA receive timer start\n");
diff --git a/src/scsi/scsi_spock.c b/src/scsi/scsi_spock.c
index 3b9f5108c..d70afca76 100644
--- a/src/scsi/scsi_spock.c
+++ b/src/scsi/scsi_spock.c
@@ -1055,7 +1055,7 @@ spock_callback(void *priv)
     spock_process_scsi(scsi, scb);
 
     period = 0.2 * ((double) scsi->temp_period);
-    timer_on(&scsi->callback_timer, (scsi->media_period + period + 10.0), 0);
+    timer_on_auto(&scsi->callback_timer, (scsi->media_period + period + 10.0));
     spock_log("Temporary period: %lf us (%" PRIi64 " periods)\n", scsi->callback_timer.period, scsi->temp_period);
 }
 
diff --git a/src/scsi/scsi_x54x.c b/src/scsi/scsi_x54x.c
index 96088e200..dc3fdfac3 100644
--- a/src/scsi/scsi_x54x.c
+++ b/src/scsi/scsi_x54x.c
@@ -1293,7 +1293,7 @@ x54x_cmd_callback(void *priv)
     }
 
     period = (1000000.0 / dev->ha_bps) * ((double) dev->temp_period);
-    timer_on(&dev->timer, dev->media_period + period + 10.0, 0);
+    timer_on_auto(&dev->timer, dev->media_period + period + 10.0);
 #if 0
     x54x_log("Temporary period: %lf us (%" PRIi64 " periods)\n", dev->timer.period, dev->temp_period);
 #endif
diff --git a/src/timer.c b/src/timer.c
index 90ee3ca49..e45fc4398 100644
--- a/src/timer.c
+++ b/src/timer.c
@@ -15,10 +15,13 @@ pc_timer_t *timer_head = NULL;
 /* Are we initialized? */
 int timer_inited = 0;
 
+static void timer_advance_ex(pc_timer_t *timer);
+
 void
 timer_enable(pc_timer_t *timer)
 {
     pc_timer_t *timer_node = timer_head;
+    int ret = 0;
 
     if (!timer_inited || (timer == NULL))
         return;
@@ -29,59 +32,63 @@ timer_enable(pc_timer_t *timer)
     if (timer->next || timer->prev)
         fatal("timer_enable - timer->next\n");
 
-    timer->flags |= TIMER_ENABLED;
-
     /*List currently empty - add to head*/
     if (!timer_head) {
         timer_head  = timer;
         timer->next = timer->prev = NULL;
         timer_target              = timer_head->ts.ts32.integer;
-        return;
-    }
-
-    if (TIMER_LESS_THAN(timer, timer_head)) {
+        ret = 1;
+    } else if (TIMER_LESS_THAN(timer, timer_head)) {
         timer->next      = timer_head;
         timer->prev      = NULL;
         timer_head->prev = timer;
         timer_head       = timer;
         timer_target     = timer_head->ts.ts32.integer;
-        return;
-    }
-
-    if (!timer_head->next) {
+        ret = 1;
+    } else if (!timer_head->next) {
         timer_head->next = timer;
         timer->prev      = timer_head;
-        return;
+        ret = 1;
     }
 
-    pc_timer_t *prev = timer_head;
-    timer_node       = timer_head->next;
+    if (ret == 0) {
+        pc_timer_t *prev = timer_head;
+        timer_node       = timer_head->next;
 
-    while (1) {
-        /*Timer expires before timer_node. Add to list in front of timer_node*/
-        if (TIMER_LESS_THAN(timer, timer_node)) {
-            timer->next      = timer_node;
-            timer->prev      = prev;
-            timer_node->prev = timer;
-            prev->next       = timer;
-            return;
+        while (1) {
+            /*Timer expires before timer_node. Add to list in front of timer_node*/
+            if (TIMER_LESS_THAN(timer, timer_node)) {
+                timer->next      = timer_node;
+                timer->prev      = prev;
+                timer_node->prev = timer;
+                prev->next       = timer;
+                ret = 1;
+                break;
+            }
+
+            /*timer_node is last in the list. Add timer to end of list*/
+            if (!timer_node->next) {
+                timer_node->next = timer;
+                timer->prev      = timer_node;
+                ret = 1;
+                break;
+            }
+
+            prev       = timer_node;
+            timer_node = timer_node->next;
         }
-
-        /*timer_node is last in the list. Add timer to end of list*/
-        if (!timer_node->next) {
-            timer_node->next = timer;
-            timer->prev      = timer_node;
-            return;
-        }
-
-        prev       = timer_node;
-        timer_node = timer_node->next;
     }
+
+    /* Do not mark it as enabled if it has failed every single condition. */
+    if (ret == 1)
+        timer->flags |= TIMER_ENABLED;
 }
 
 void
 timer_disable(pc_timer_t *timer)
 {
+    pc_timer_t *cur, *temp;
+
     if (!timer_inited || (timer == NULL) || !(timer->flags & TIMER_ENABLED))
         return;
 
@@ -120,13 +127,15 @@ timer_process(void)
         timer->next = timer->prev = NULL;
         timer->flags &= ~TIMER_ENABLED;
 
+        timer->flags |= TIMER_PROCESS;
         if (timer->flags & TIMER_SPLIT)
-            timer_advance_ex(timer, 0);   /* We're splitting a > 1 s period into multiple <= 1 s periods. */
-        else if (timer->callback != NULL) {/* Make sure it's no NULL, so that we can have a NULL callback when no operation is needed. */
-            timer->flags |= TIMER_PROCESS;
+            timer_advance_ex(timer);      /* We're splitting a > 1 s period into
+                                             multiple <= 1 s periods. */
+        else if (timer->callback != NULL) /* Make sure it's not NULL, so that we can
+                                             have a NULL callback when no operation
+                                             is needed. */
             timer->callback(timer->priv);
-            timer->flags &= ~TIMER_PROCESS;
-        }
+        timer->flags &= ~TIMER_PROCESS;
     }
 
     timer_target = timer_head->ts.ts32.integer;
@@ -182,60 +191,47 @@ timer_stop(pc_timer_t *timer)
         return;
 
     timer->period = 0.0;
-    timer_disable(timer);
+    if (timer_is_enabled(timer))
+        timer_disable(timer);
     timer->flags &= ~TIMER_SPLIT;
 }
 
 static void
-timer_do_period(pc_timer_t *timer, uint64_t period, int start)
+timer_do_period(pc_timer_t *timer, uint64_t period)
 {
-    if (!timer_inited || (timer == NULL))
-        return;
-
-    if (start)
-        timer_set_delay_u64(timer, period);
-    else
+    if (timer->flags & TIMER_PROCESS)
         timer_advance_u64(timer, period);
+    else
+        timer_set_delay_u64(timer, period);
 }
 
-void
-timer_advance_ex(pc_timer_t *timer, int start)
+static void
+timer_advance_ex(pc_timer_t *timer)
 {
-    if (!timer_inited || (timer == NULL))
-        return;
+    double dusec = ((double) TIMER_USEC);
+    double period;
 
-    if (timer->period > MAX_USEC) {
-        timer_do_period(timer, MAX_USEC64 * TIMER_USEC, start);
-        timer->period -= MAX_USEC;
-        timer->flags |= TIMER_SPLIT;
-    } else {
-        if (timer->period > 0.0)
-            timer_do_period(timer, (uint64_t) (timer->period * ((double) TIMER_USEC)), start);
-        else
-            timer_disable(timer);
-        timer->period = 0.0;
+    period = (timer->period > MAX_USEC) ? MAX_USEC64 : timer->period;
+
+    if (timer->period > 0.0) {
+        timer_do_period(timer, (uint64_t) (period * dusec));
+        timer->period -= period;
+        timer->flags = (timer->flags & ~TIMER_SPLIT) | ((timer->period > MAX_USEC) ? TIMER_SPLIT : 0);
+    } else if (timer_is_enabled(timer)) {
+        timer_disable(timer);
         timer->flags &= ~TIMER_SPLIT;
     }
 }
 
-void
-timer_on(pc_timer_t *timer, double period, int start)
-{
-    if (!timer_inited || (timer == NULL))
-        return;
-
-    timer->period = period;
-    timer_advance_ex(timer, start);
-}
-
 void
 timer_on_auto(pc_timer_t *timer, double period)
 {
     if (!timer_inited || (timer == NULL))
         return;
 
-    if (period > 0.0)
-        timer_on(timer, period, !(timer->flags & TIMER_PROCESS) && (timer->period <= 0.0));
-    else
+    if (period > 0.0) {
+        timer->period = period;
+        timer_advance_ex(timer);
+    } else if (timer_is_on(timer))
         timer_stop(timer);
 }