diff --git a/src/chipset/ali1543.c b/src/chipset/ali1543.c
index 6d03b3a12..00146c90e 100644
--- a/src/chipset/ali1543.c
+++ b/src/chipset/ali1543.c
@@ -1430,7 +1430,7 @@ ali7101_read(int func, int addr, void *priv)
 }
 
 static void
-ali5237_usb_raise_interrupt(void *priv)
+ali5237_usb_raise_interrupt(usb_t* usb, void *priv)
 {
     ali1543_t *dev = (ali1543_t *) priv;
 
diff --git a/src/include/86box/usb.h b/src/include/86box/usb.h
index 39ddf9cf6..af1922570 100644
--- a/src/include/86box/usb.h
+++ b/src/include/86box/usb.h
@@ -36,7 +36,13 @@ typedef struct
 /* USB Host Controller device struct */
 typedef struct usb_t
 {
-    uint8_t       uhci_io[32], ohci_mmio[4096];
+    union
+    {
+        uint8_t  ohci_mmio[4096];
+        uint16_t ohci_mmio_w[2048];
+        uint32_t ohci_mmio_l[1024];
+    };
+    uint8_t       uhci_io[32];
     uint16_t      uhci_io_base;
     int           uhci_enable, ohci_enable;
     uint32_t      ohci_mem_base;
diff --git a/src/usb.c b/src/usb.c
index 0951412d6..cde3ee4a9 100644
--- a/src/usb.c
+++ b/src/usb.c
@@ -63,7 +63,7 @@ enum
     OHCI_HcBulkHeadED = 0x28,
     OHCI_HcBulkCurrentED = 0x2C,
     OHCI_HcDoneHead = 0x30,
-    OHCI_HcFMInterval = 0x34,
+    OHCI_HcFmInterval = 0x34,
     OHCI_HcFmRemaining = 0x38,
     OHCI_HcFmNumber = 0x3C,
     OHCI_HcPeriodicStart = 0x40,
@@ -223,10 +223,50 @@ ohci_mmio_read(uint32_t addr, void *p)
     return ret;
 }
 
+void
+ohci_set_interrupt(usb_t* usb, uint8_t bit)
+{
+    if (!(usb->ohci_mmio[OHCI_HcInterruptEnable + 3] & 0x80))
+        return;
+    
+    if (!(usb->ohci_mmio[OHCI_HcInterruptEnable] & bit))
+        return;
+
+    if (usb->ohci_mmio[OHCI_HcInterruptDisable] & bit)
+        return;
+
+    usb->ohci_mmio[OHCI_HcInterruptStatus] |= bit;
+    usb_interrupt_ohci(usb);
+}
+
+void
+ohci_end_of_frame(usb_t* dev)
+{
+    /* TODO: Put endpoint and transfer descriptor processing here. */
+}
+
+void
+ohci_start_of_frame(usb_t* dev)
+{
+    ohci_set_interrupt(dev, OHCI_HcInterruptEnable_SO);
+}
+
 void
 ohci_update_frame_counter(void* priv)
 {
     usb_t *dev = (usb_t *) priv;
+
+    dev->ohci_mmio_w[OHCI_HcFmRemaining / 2] &= 0x3fff;
+    if (dev->ohci_mmio_w[OHCI_HcFmRemaining / 2] == 0) {
+        ohci_end_of_frame(dev);
+        dev->ohci_mmio_w[OHCI_HcFmRemaining / 2] = dev->ohci_mmio_w[OHCI_HcFmInterval / 2] & 0x3fff;
+        dev->ohci_mmio_l[OHCI_HcFmRemaining / 4] &= ~(1 << 31);
+        dev->ohci_mmio_l[OHCI_HcFmRemaining / 4] |= dev->ohci_mmio_l[OHCI_HcFmInterval / 4] & (1 << 31);
+        dev->ohci_mmio_w[OHCI_HcFmNumber / 2]++;
+        ohci_start_of_frame(dev);
+    }
+    if (dev->ohci_mmio_w[OHCI_HcFmRemaining / 2]) dev->ohci_mmio_w[OHCI_HcFmRemaining / 2]--;
+    timer_on_auto(&dev->ohci_frame_timer, 1. / (12. * 1000. * 1000.));
 }
 
 void
@@ -257,23 +297,6 @@ ohci_port_reset_callback_2(void* priv)
     dev->ohci_mmio[OHCI_HcRhPortStatus2] &= ~0x10;
     dev->ohci_mmio[OHCI_HcRhPortStatus2 + 2] |= 0x10;
 }
-
-void
-ohci_set_interrupt(usb_t* usb, uint8_t bit)
-{
-    if (!(usb->ohci_mmio[OHCI_HcInterruptEnable + 3] & 0x80))
-        return;
-    
-    if (!(usb->ohci_mmio[OHCI_HcInterruptEnable] & bit))
-        return;
-
-    if (usb->ohci_mmio[OHCI_HcInterruptDisable] & bit)
-        return;
-
-    usb->ohci_mmio[OHCI_HcInterruptStatus] |= bit;
-    usb_interrupt_ohci(usb);
-}
-
 static void
 ohci_mmio_write(uint32_t addr, uint8_t val, void *p)
 {