diff --git a/hw/acpi.c b/hw/acpi.c
index 08cb126..07283be 100644
--- a/hw/acpi.c
+++ b/hw/acpi.c
@@ -15,6 +15,7 @@
  * You should have received a copy of the GNU Lesser General Public
  * License along with this library; if not, see <http://www.gnu.org/licenses/>
  */
+#include "sysemu.h"
 #include "hw.h"
 #include "pc.h"
 #include "acpi.h"
@@ -198,6 +199,42 @@ out:
     return -1;
 }
 
+/* ACPI PM1a EVT */
+uint16_t acpi_pm1_evt_get_sts(ACPIPM1EVT *pm1, int64_t overflow_time)
+{
+    int64_t d = acpi_pm_tmr_get_clock();
+    if (d >= overflow_time) {
+        pm1->sts |= ACPI_BITMASK_TIMER_STATUS;
+    }
+    return pm1->sts;
+}
+
+void acpi_pm1_evt_write_sts(ACPIPM1EVT *pm1, ACPIPMTimer *tmr, uint16_t val)
+{
+    uint16_t pm1_sts = acpi_pm1_evt_get_sts(pm1, tmr->overflow_time);
+    if (pm1_sts & val & ACPI_BITMASK_TIMER_STATUS) {
+        /* if TMRSTS is reset, then compute the new overflow time */
+        acpi_pm_tmr_calc_overflow_time(tmr);
+    }
+    pm1->sts &= ~val;
+}
+
+void acpi_pm1_evt_power_down(ACPIPM1EVT *pm1, ACPIPMTimer *tmr)
+{
+    if (!pm1) {
+        qemu_system_shutdown_request();
+    } else if (pm1->en & ACPI_BITMASK_POWER_BUTTON_ENABLE) {
+        pm1->sts |= ACPI_BITMASK_POWER_BUTTON_STATUS;
+        tmr->update_sci(tmr);
+    }
+}
+
+void acpi_pm1_evt_reset(ACPIPM1EVT *pm1)
+{
+    pm1->sts = 0;
+    pm1->en = 0;
+}
+
 /* ACPI PM_TMR */
 void acpi_pm_tmr_update(ACPIPMTimer *tmr, bool enable)
 {
diff --git a/hw/acpi.h b/hw/acpi.h
index fc42501..c286d7d 100644
--- a/hw/acpi.h
+++ b/hw/acpi.h
@@ -99,4 +99,17 @@ static inline int64_t acpi_pm_tmr_get_clock(void)
                     get_ticks_per_sec());
 }
 
+/* PM1a_EVT: piix and ich9 don't implement PM1b. */
+struct ACPIPM1EVT
+{
+    uint16_t sts;
+    uint16_t en;
+};
+typedef struct ACPIPM1EVT ACPIPM1EVT;
+
+uint16_t acpi_pm1_evt_get_sts(ACPIPM1EVT *pm1, int64_t overflow_time);
+void acpi_pm1_evt_write_sts(ACPIPM1EVT *pm1, ACPIPMTimer *tmr, uint16_t val);
+void acpi_pm1_evt_power_down(ACPIPM1EVT *pm1, ACPIPMTimer *tmr);
+void acpi_pm1_evt_reset(ACPIPM1EVT *pm1);
+
 #endif /* !QEMU_HW_ACPI_H */
diff --git a/hw/acpi_piix4.c b/hw/acpi_piix4.c
index d5f631a..5b4eef5 100644
--- a/hw/acpi_piix4.c
+++ b/hw/acpi_piix4.c
@@ -54,8 +54,7 @@ struct pci_status {
 typedef struct PIIX4PMState {
     PCIDevice dev;
     IORange ioport;
-    uint16_t pmsts;
-    uint16_t pmen;
+    ACPIPM1EVT pm1a;
     uint16_t pmcntrl;
 
     APMState apm;
@@ -81,20 +80,12 @@ static void piix4_acpi_system_hot_add_init(PCIBus *bus, PIIX4PMState *s);
 #define ACPI_ENABLE 0xf1
 #define ACPI_DISABLE 0xf0
 
-static int get_pmsts(PIIX4PMState *s)
-{
-    int64_t d = acpi_pm_tmr_get_clock();
-    if (d >= s->tmr.overflow_time)
-        s->pmsts |= ACPI_BITMASK_TIMER_STATUS;
-    return s->pmsts;
-}
-
 static void pm_update_sci(PIIX4PMState *s)
 {
     int sci_level, pmsts;
 
-    pmsts = get_pmsts(s);
-    sci_level = (((pmsts & s->pmen) &
+    pmsts = acpi_pm1_evt_get_sts(&s->pm1a, s->tmr.overflow_time);
+    sci_level = (((pmsts & s->pm1a.en) &
                   (ACPI_BITMASK_RT_CLOCK_ENABLE |
                    ACPI_BITMASK_POWER_BUTTON_ENABLE |
                    ACPI_BITMASK_GLOBAL_LOCK_ENABLE |
@@ -103,7 +94,7 @@ static void pm_update_sci(PIIX4PMState *s)
 
     qemu_set_irq(s->irq, sci_level);
     /* schedule a timer interruption if needed */
-    acpi_pm_tmr_update(&s->tmr, (s->pmen & ACPI_BITMASK_TIMER_ENABLE) &&
+    acpi_pm_tmr_update(&s->tmr, (s->pm1a.en & ACPI_BITMASK_TIMER_ENABLE) &&
                        !(pmsts & ACPI_BITMASK_TIMER_STATUS));
 }
 
@@ -125,19 +116,11 @@ static void pm_ioport_write(IORange *ioport, uint64_t addr, unsigned width,
 
     switch(addr) {
     case 0x00:
-        {
-            int pmsts;
-            pmsts = get_pmsts(s);
-            if (pmsts & val & ACPI_BITMASK_TIMER_STATUS) {
-                /* if TMRSTS is reset, then compute the new overflow time */
-                acpi_pm_tmr_calc_overflow_time(&s->tmr);
-            }
-            s->pmsts &= ~val;
-            pm_update_sci(s);
-        }
+        acpi_pm1_evt_write_sts(&s->pm1a, &s->tmr, val);
+        pm_update_sci(s);
         break;
     case 0x02:
-        s->pmen = val;
+        s->pm1a.en = val;
         pm_update_sci(s);
         break;
     case 0x04:
@@ -154,8 +137,8 @@ static void pm_ioport_write(IORange *ioport, uint64_t addr, unsigned width,
                 case 1:
                     /* ACPI_BITMASK_WAKE_STATUS should be set on resume.
                        Pretend that resume was caused by power button */
-                    s->pmsts |= (ACPI_BITMASK_WAKE_STATUS |
-                                 ACPI_BITMASK_POWER_BUTTON_STATUS);
+                    s->pm1a.sts |= (ACPI_BITMASK_WAKE_STATUS |
+                                    ACPI_BITMASK_POWER_BUTTON_STATUS);
                     qemu_system_reset_request();
                     if (s->cmos_s3) {
                         qemu_irq_raise(s->cmos_s3);
@@ -180,10 +163,10 @@ static void pm_ioport_read(IORange *ioport, uint64_t addr, unsigned width,
 
     switch(addr) {
     case 0x00:
-        val = get_pmsts(s);
+        val = acpi_pm1_evt_get_sts(&s->pm1a, s->tmr.overflow_time);
         break;
     case 0x02:
-        val = s->pmen;
+        val = s->pm1a.en;
         break;
     case 0x04:
         val = s->pmcntrl;
@@ -290,8 +273,8 @@ static const VMStateDescription vmstate_acpi = {
     .post_load = vmstate_acpi_post_load,
     .fields      = (VMStateField []) {
         VMSTATE_PCI_DEVICE(dev, PIIX4PMState),
-        VMSTATE_UINT16(pmsts, PIIX4PMState),
-        VMSTATE_UINT16(pmen, PIIX4PMState),
+        VMSTATE_UINT16(pm1a.sts, PIIX4PMState),
+        VMSTATE_UINT16(pm1a.en, PIIX4PMState),
         VMSTATE_UINT16(pmcntrl, PIIX4PMState),
         VMSTATE_STRUCT(apm, PIIX4PMState, 0, vmstate_apm, APMState),
         VMSTATE_TIMER(tmr.timer, PIIX4PMState),
@@ -342,13 +325,10 @@ static void piix4_reset(void *opaque)
 static void piix4_powerdown(void *opaque, int irq, int power_failing)
 {
     PIIX4PMState *s = opaque;
+    ACPIPM1EVT *pm1a = s? &s->pm1a: NULL;
+    ACPIPMTimer *tmr = s? &s->tmr: NULL;
 
-    if (!s) {
-        qemu_system_shutdown_request();
-    } else if (s->pmen & ACPI_BITMASK_POWER_BUTTON_ENABLE) {
-        s->pmsts |= ACPI_BITMASK_POWER_BUTTON_STATUS;
-        pm_update_sci(s);
-    }
+    acpi_pm1_evt_power_down(pm1a, tmr);
 }
 
 static int piix4_pm_initfn(PCIDevice *dev)
diff --git a/hw/vt82c686.c b/hw/vt82c686.c
index 6f9c384..10cbc74 100644
--- a/hw/vt82c686.c
+++ b/hw/vt82c686.c
@@ -156,8 +156,7 @@ static void vt82c686b_write_config(PCIDevice * d, uint32_t address,
 
 typedef struct VT686PMState {
     PCIDevice dev;
-    uint16_t pmsts;
-    uint16_t pmen;
+    ACPIPM1EVT pm1a;
     uint16_t pmcntrl;
     APMState apm;
     ACPIPMTimer tmr;
@@ -173,34 +172,19 @@ typedef struct VT686MC97State {
     PCIDevice dev;
 } VT686MC97State;
 
-#define RTC_EN    (1 << 10)
-#define PWRBTN_EN (1 << 8)
-#define GBL_EN    (1 << 5)
-#define TMROF_EN  (1 << 0)
-#define SUS_EN    (1 << 13)
-
-#define ACPI_ENABLE  0xf1
-#define ACPI_DISABLE 0xf0
-
-static int get_pmsts(VT686PMState *s)
-{
-    int64_t d = acpi_pm_tmr_get_clock();
-    if (d >= s->tmr.overflow_time) {
-        s->pmsts |= ACPI_BITMASK_TIMER_STATUS;
-    }
-    return s->pmsts;
-}
-
 static void pm_update_sci(VT686PMState *s)
 {
     int sci_level, pmsts;
 
-    pmsts = get_pmsts(s);
-    sci_level = (((pmsts & s->pmen) &
-                  (RTC_EN | PWRBTN_EN | GBL_EN | TMROF_EN)) != 0);
+    pmsts = acpi_pm1_evt_get_sts(&s->pm1a, s->tmr.overflow_time);
+    sci_level = (((pmsts & s->pm1a.en) &
+                  (ACPI_BITMASK_RT_CLOCK_ENABLE |
+                   ACPI_BITMASK_POWER_BUTTON_ENABLE |
+                   ACPI_BITMASK_GLOBAL_LOCK_ENABLE |
+                   ACPI_BITMASK_TIMER_ENABLE)) != 0);
     qemu_set_irq(s->dev.irq[0], sci_level);
     /* schedule a timer interruption if needed */
-    acpi_pm_tmr_update(&s->tmr, (s->pmen & ACPI_BITMASK_TIMER_ENABLE) &&
+    acpi_pm_tmr_update(&s->tmr, (s->pm1a.en & ACPI_BITMASK_TIMER_ENABLE) &&
                        !(pmsts & ACPI_BITMASK_TIMER_STATUS));
 }
 
@@ -217,19 +201,11 @@ static void pm_ioport_writew(void *opaque, uint32_t addr, uint32_t val)
     addr &= 0x0f;
     switch (addr) {
     case 0x00:
-        {
-            int pmsts;
-            pmsts = get_pmsts(s);
-            if (pmsts & val & TMROF_EN) {
-                /* if TMRSTS is reset, then compute the new overflow time */
-                acpi_pm_tmr_calc_overflow_time(&s->tmr);
-            }
-            s->pmsts &= ~val;
-            pm_update_sci(s);
-        }
+        acpi_pm1_evt_write_sts(&s->pm1a, &s->tmr, val);
+        pm_update_sci(s);
         break;
     case 0x02:
-        s->pmen = val;
+        s->pm1a.en = val;
         pm_update_sci(s);
         break;
     case 0x04:
@@ -263,10 +239,10 @@ static uint32_t pm_ioport_readw(void *opaque, uint32_t addr)
     addr &= 0x0f;
     switch (addr) {
     case 0x00:
-        val = get_pmsts(s);
+        val = acpi_pm1_evt_get_sts(&s->pm1a, s->tmr.overflow_time);
         break;
     case 0x02:
-        val = s->pmen;
+        val = s->pm1a.en;
         break;
     case 0x04:
         val = s->pmcntrl;
@@ -344,8 +320,8 @@ static const VMStateDescription vmstate_acpi = {
     .post_load = vmstate_acpi_post_load,
     .fields      = (VMStateField []) {
         VMSTATE_PCI_DEVICE(dev, VT686PMState),
-        VMSTATE_UINT16(pmsts, VT686PMState),
-        VMSTATE_UINT16(pmen, VT686PMState),
+        VMSTATE_UINT16(pm1a.sts, VT686PMState),
+        VMSTATE_UINT16(pm1a.en, VT686PMState),
         VMSTATE_UINT16(pmcntrl, VT686PMState),
         VMSTATE_STRUCT(apm, VT686PMState, 0, vmstate_apm, APMState),
         VMSTATE_TIMER(tmr.timer, VT686PMState),
