diff --git a/src/include/86box/machine.h b/src/include/86box/machine.h
index 6d893e8ac..3fb3f5f9c 100644
--- a/src/include/86box/machine.h
+++ b/src/include/86box/machine.h
@@ -372,15 +372,18 @@ extern int         machine_has_mouse(void);
 extern int         machine_is_sony(void);
 
 extern uint8_t  machine_get_p1(void);
+extern void     machine_set_p1_default(uint8_t val);
 extern void     machine_set_p1(uint8_t val);
 extern void     machine_init_p1(void);
 extern uint8_t  machine_handle_p1(uint8_t write, uint8_t val);
 extern uint32_t machine_get_gpio(void);
+extern void     machine_set_gpio_default(uint32_t val);
 extern void     machine_set_gpio(uint32_t val);
 extern void     machine_init_gpio(void);
 extern uint32_t machine_handle_gpio(uint8_t write, uint32_t val);
 extern uint32_t machine_get_gpio_acpi(void);
-extern void     machine_set_gpio_acpi(uint32_t gpio_val);
+extern void     machine_set_gpio_acpi_default(uint32_t val);
+extern void     machine_set_gpio_acpi(uint32_t val);
 extern void     machine_init_gpio_acpi(void);
 extern uint32_t machine_handle_gpio_acpi(uint8_t write, uint32_t val);
 
diff --git a/src/machine/m_at_socket5.c b/src/machine/m_at_socket5.c
index a75d87a96..8681c6995 100644
--- a/src/machine/m_at_socket5.c
+++ b/src/machine/m_at_socket5.c
@@ -158,6 +158,41 @@ machine_at_apollo_init(const machine_t *model)
     return ret;
 }
 
+static void
+machine_at_zappa_gpio_init(void)
+{
+    uint32_t gpio = 0xffffffff;
+
+    /* Register 0x0079: */
+    /* Bit 7: 0 = Clear password, 1 = Keep password. */
+    /* Bit 6: 0 = NVRAM cleared by jumper, 1 = NVRAM normal. */
+    /* Bit 5: 0 = CMOS Setup disabled, 1 = CMOS Setup enabled. */
+    /* Bit 4: External CPU clock (Switch 8). */
+    /* Bit 3: External CPU clock (Switch 7). */
+    /*        50 MHz: Switch 7 = Off, Switch 8 = Off. */
+    /*        60 MHz: Switch 7 = On, Switch 8 = Off. */
+    /*        66 MHz: Switch 7 = Off, Switch 8 = On. */
+    /* Bit 2: No Connect. */
+    /* Bit 1: No Connect. */
+    /* Bit 0: 0 = 1.5x multiplier, 1 = 2x multiplier (Switch 6). */
+    /* NOTE: A bit is read as 1 if switch is off, and as 0 if switch is on. */
+    gpio = 0xffffe6ff;
+
+    if (cpu_busspeed <= 50000000)
+        gpio |= 0xffff10ff;
+    else if ((cpu_busspeed > 50000000) && (cpu_busspeed <= 60000000))
+        gpio |= 0xffff18ff;
+    else if (cpu_busspeed > 60000000)
+        gpio |= 0xffff00ff;
+
+    if (cpu_dmulti <= 1.5)
+        gpio |= 0xffff01ff;
+    else
+        gpio |= 0xffff00ff;
+
+    machine_set_gpio_default(gpio);
+}
+
 int
 machine_at_zappa_init(const machine_t *model)
 {
@@ -171,6 +206,7 @@ machine_at_zappa_init(const machine_t *model)
         return ret;
 
     machine_at_common_init_ex(model, 2);
+    machine_at_zappa_gpio_init();
 
     pci_init(PCI_CONFIG_TYPE_1);
     pci_register_slot(0x00, PCI_CARD_NORTHBRIDGE, 0, 0, 0, 0);
diff --git a/src/machine/machine_table.c b/src/machine/machine_table.c
index 10b62c8fe..4df1985c7 100644
--- a/src/machine/machine_table.c
+++ b/src/machine/machine_table.c
@@ -13278,10 +13278,16 @@ machine_get_p1(void)
     return machine_p1;
 }
 
+void
+machine_set_p1_default(uint8_t val)
+{
+    machine_p1 = machine_p1_default = val;
+}
+
 void
 machine_set_p1(uint8_t val)
 {
-    machine_p1 = machines[machine].kbc_p1 & val;
+    machine_p1 = machine_p1_default & val;
 }
 
 
@@ -13294,7 +13300,7 @@ machine_handle_p1(uint8_t write, uint8_t val)
         ret = machines[machine].p1_handler(write, val);
     else {
         if (write)
-            machine_p1 = machines[machine].kbc_p1 & val;
+            machine_p1 = machine_p1_default & val;
         else
             ret = machine_p1;
     }
@@ -13314,10 +13320,16 @@ machine_get_gpio(void)
     return machine_gpio;
 }
 
+void
+machine_set_gpio_default(uint32_t val)
+{
+    machine_gpio = machine_gpio_default = val;
+}
+
 void
 machine_set_gpio(uint32_t val)
 {
-    machine_gpio = machines[machine].gpio & val;
+    machine_gpio = machine_gpio_default & val;
 }
 
 uint32_t
@@ -13329,7 +13341,7 @@ machine_handle_gpio(uint8_t write, uint32_t val)
         ret = machines[machine].gpio_handler(write, val);
     else {
         if (write)
-            machine_gpio = machines[machine].gpio & val;
+            machine_gpio = machine_gpio_default & val;
         else
             ret = machine_gpio;
     }
@@ -13349,10 +13361,16 @@ machine_get_gpio_acpi(void)
     return machine_gpio_acpi;
 }
 
+void
+machine_set_gpio_acpi_default(uint32_t val)
+{
+    machine_gpio_acpi = machine_gpio_acpi_default = val;
+}
+
 void
 machine_set_gpio_acpi(uint32_t val)
 {
-    machine_gpio_acpi = machines[machine].gpio_acpi & val;
+    machine_gpio_acpi = machine_gpio_acpi_default & val;
 }
 
 uint32_t
@@ -13364,7 +13382,7 @@ machine_handle_gpio_acpi(uint8_t write, uint32_t val)
         ret = machines[machine].gpio_acpi_handler(write, val);
     else {
         if (write)
-            machine_gpio_acpi = machines[machine].gpio_acpi & val;
+            machine_gpio_acpi = machine_gpio_acpi_default & val;
         else
             ret = machine_gpio_acpi;
     }