diff --git a/hw/pc98sys.c b/hw/pc98sys.c
new file mode 100644
index 0000000..43a910a
--- /dev/null
+++ b/hw/pc98sys.c
@@ -0,0 +1,482 @@
+/*
+ * QEMU NEC PC-9821 systemp port
+ *
+ * Copyright (c) 2009 TAKEDA, toshiya
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+#include "hw.h"
+#include "pc.h"
+#include "qemu-timer.h"
+#include "isa.h"
+#include "qdev-addr.h"
+#include "loader.h"
+
+enum {
+    RTC_STROBE = 0x08,
+    RTC_CLOCK  = 0x10,
+    RTC_DIN    = 0x20,
+};
+
+enum {
+    RTC_CMD_SHIFT  = 0x01,
+    RTC_CMD_READ   = 0x03,
+    RTC_CMD_EXMODE = 0x07,
+};
+
+enum {
+    RTC_MODE_UPD4993A = 0x20,
+};
+
+#define TSTMP_FREQ 307200
+
+struct SysPortState {
+    uint8_t rtc_mode;
+    uint8_t rtc_reg;
+    uint8_t rtc_cmd;
+    uint64_t rtc_shift_out;
+    uint8_t rtc_shift_cmd;
+    uint8_t rtc_irq_mode;
+    uint8_t rtc_irq_count;
+
+    uint8_t sys_portc;
+    int sys_portc_patch;
+    uint8_t prn_porta;
+    uint8_t prn_portc;
+
+    uint8_t sdip[24];
+    uint8_t sdip_bank;
+
+    QEMUTimer *rtc_timer;
+    qemu_irq irq;
+    int64_t tstmp_initial_clock;
+};
+
+typedef struct ISASysPortState {
+    ISADevice dev;
+    uint32_t isairq;
+    struct SysPortState state;
+} ISASysPortState;
+
+typedef struct SysPortState SysPortState;
+
+/* NEC uPD4993A RTC */
+
+// 1000/64 = 15.625
+static const int rtc_period[8] = { 15, 16, 16, 15, 16, 16, 15, 16 };
+static int rtc_period_ptr = 0;
+
+static void rtc_timer_handler(void *opaque)
+{
+    SysPortState *s = opaque;
+
+    /* rtc_irq_mode = 0 : 1/64 sec
+                    = 1 : 1/32 sec
+                    = 2 : no irq
+                    = 3 : 1/16 sec
+    */
+    if ((s->rtc_irq_mode & 0x03) != 2) {
+        if (++s->rtc_irq_count > (s->rtc_irq_mode & 0x03)) {
+            qemu_set_irq(s->irq, 1);
+            s->rtc_irq_count = 0;
+        }
+    }
+
+    /* set next timer */
+    qemu_mod_timer(s->rtc_timer, qemu_get_clock(rt_clock) +
+                   rtc_period[(rtc_period_ptr++) & 7]);
+}
+
+static void rtc_read_time(void *opaque)
+{
+    SysPortState *s = opaque;
+    struct tm tm;
+
+    qemu_get_timedate(&tm, 0);
+    s->rtc_shift_out = (uint64_t)to_bcd(tm.tm_sec);
+    s->rtc_shift_out |= (uint64_t)to_bcd(tm.tm_min) << 8;
+    s->rtc_shift_out |= (uint64_t)to_bcd(tm.tm_hour) << 16;
+    s->rtc_shift_out |= (uint64_t)to_bcd(tm.tm_mday) << 24;
+    s->rtc_shift_out |= (uint64_t)tm.tm_wday << 32;
+    s->rtc_shift_out |= (uint64_t)(tm.tm_mon + 1) << 36;
+    s->rtc_shift_out |= (uint64_t)to_bcd(tm.tm_year % 100) << 40;
+    if (s->rtc_mode & RTC_MODE_UPD4993A) {
+        s->rtc_shift_out <<= 4;
+    }
+}
+
+static void rtc_reg_write(void *opaque, uint32_t addr, uint32_t value)
+{
+    SysPortState *s = opaque;
+
+    if ((s->rtc_reg & RTC_STROBE) && !(value & RTC_STROBE)) {
+        s->rtc_cmd = s->rtc_reg & 0x07;
+        if (s->rtc_cmd == RTC_CMD_READ) {
+            rtc_read_time(s);
+        } else if (s->rtc_cmd == RTC_CMD_EXMODE) {
+            s->rtc_cmd = s->rtc_shift_cmd & 0x0f;
+            if (s->rtc_cmd == RTC_CMD_READ) {
+                rtc_read_time(s);
+            }
+        }
+    }
+    if ((s->rtc_reg & RTC_CLOCK) && !(value & RTC_CLOCK)) {
+        uint8_t din = ((s->rtc_reg & RTC_DIN) != 0);
+//        if ((s->rtc_reg & 0x07) == RTC_CMD_EXMODE) {
+            s->rtc_shift_cmd |= din << 4;
+            s->rtc_shift_cmd >>= 1;
+//        } else if (s->rtc_cmd == RTC_CMD_SHIFT) {
+            s->rtc_shift_out >>= 1;
+//        }
+    }
+    s->rtc_reg = value;
+}
+
+static void rtc_mode_write(void *opaque, uint32_t addr, uint32_t value)
+{
+    SysPortState *s = opaque;
+
+    s->rtc_mode = value;
+}
+
+static uint32_t rtc_mode_read(void *opaque, uint32_t addr)
+{
+    SysPortState *s = opaque;
+
+    return s->rtc_mode;
+}
+
+static void rtc_irq_mode_write(void *opaque, uint32_t addr, uint32_t value)
+{
+    SysPortState *s = opaque;
+
+    s->rtc_irq_mode = value;
+    s->rtc_irq_count = 0;
+}
+
+static uint32_t rtc_irq_mode_read(void *opaque, uint32_t addr)
+{
+    SysPortState *s = opaque;
+
+    qemu_set_irq(s->irq, 0);
+    return s->rtc_irq_mode;
+}
+
+/* system port */
+
+static uint32_t sys_porta_read(void *opaque, uint32_t addr)
+{
+    return 0x73;
+}
+
+static uint32_t sys_portb_read(void *opaque, uint32_t addr)
+{
+    SysPortState *s = opaque;
+
+    return 0xf8 | (s->rtc_shift_out & 1);
+}
+
+static void sys_portc_write(void *opaque, uint32_t addr, uint32_t value)
+{
+    SysPortState *s = opaque;
+
+    s->sys_portc = value;
+    pc98_pcspk_write(value);
+}
+
+static uint32_t sys_portc_read(void *opaque, uint32_t addr)
+{
+    SysPortState *s = opaque;
+
+    if (s->sys_portc_patch) {
+        /* itf protect mode patch */
+        s->sys_portc_patch--;
+        if (s->sys_portc_patch == 0 || s->sys_portc_patch == 4) {
+            s->sys_portc |= 0x20;
+        }
+    }
+    return s->sys_portc;
+}
+
+static void sys_ctrl_write(void *opaque, uint32_t addr, uint32_t value)
+{
+    SysPortState *s = opaque;
+
+    if (!(value & 0x80)) {
+        /* set/reset portc bit */
+        uint32_t portc = s->sys_portc;
+        uint32_t bit = 1 << ((value >> 1) & 7);
+        if (value & 1) {
+            portc |= bit;
+        } else {
+            portc &= ~bit;
+        }
+        sys_portc_write(s, 0, portc);
+    }
+}
+
+uint8_t pc98_sys_read_shut(void *opaque)
+{
+    SysPortState *s = opaque;
+
+    return ((s->sys_portc & 0xa0) == 0xa0);
+}
+
+/* printer port */
+
+static void prn_porta_write(void *opaque, uint32_t addr, uint32_t value)
+{
+    SysPortState *s = opaque;
+
+    s->prn_porta = value;
+}
+
+static uint32_t prn_porta_read(void *opaque, uint32_t addr)
+{
+    SysPortState *s = opaque;
+
+    return s->prn_porta;
+}
+
+static uint32_t prn_portb_read(void *opaque, uint32_t addr)
+{
+#ifdef PC98_SYSCLOCK_5MHZ
+    return 0x94;
+#else
+    return 0xb4;
+#endif
+}
+
+static void prn_portc_write(void *opaque, uint32_t addr, uint32_t value)
+{
+    SysPortState *s = opaque;
+
+    s->prn_portc = value;
+}
+
+static uint32_t prn_portc_read(void *opaque, uint32_t addr)
+{
+    SysPortState *s = opaque;
+
+    return s->prn_portc;
+}
+
+static void prn_ctrl_write(void *opaque, uint32_t addr, uint32_t value)
+{
+    SysPortState *s = opaque;
+
+    if (!(value & 0x80)) {
+        /* set/reset portc bit */
+        uint8_t portc = s->prn_portc;
+        uint8_t bit = 1 << ((value >> 1) & 7);
+        if (value & 1) {
+            portc |= bit;
+        } else {
+            portc &= ~bit;
+        }
+        prn_portc_write(s, 0, portc);
+    }
+}
+
+/* time stamper */
+
+static uint32_t tstmp_read(void *opaque, uint32_t addr)
+{
+    SysPortState *s = opaque;
+    uint64_t d = muldiv64(qemu_get_clock(vm_clock) - s->tstmp_initial_clock,
+                          TSTMP_FREQ, get_ticks_per_sec());
+
+    switch(addr) {
+    case 0x5c:
+        return d & 0xffff;
+    case 0x5e:
+        return (d >> 8) & 0xffff;
+    }
+    return 0xffff;
+}
+
+/* software dip-switch */
+
+static void sdip_data_write(void *opaque, uint32_t addr, uint32_t value)
+{
+    SysPortState *s = opaque;
+    uint8_t bank;
+
+    if (s->sdip_bank & 0x40) {
+        bank = ((addr >> 8) & 0x0f) + 8;
+    } else {
+        bank = ((addr >> 8) & 0x0f) - 4;
+    }
+    s->sdip[bank] = value;
+}
+
+static uint32_t sdip_data_read(void *opaque, uint32_t addr)
+{
+    SysPortState *s = opaque;
+    uint8_t bank;
+ 
+    if (s->sdip_bank & 0x40) {
+        bank = ((addr >> 8) & 0x0f) + 8;
+    } else {
+        bank = ((addr >> 8) & 0x0f) - 4;
+    }
+    return s->sdip[bank];
+}
+
+static void sdip_bank_write(void *opaque, uint32_t addr, uint32_t value)
+{
+    SysPortState *s = opaque;
+
+    s->sdip_bank = value;
+}
+
+/* interface */
+
+static void pc98_sys_reset(void *opaque)
+{
+    SysPortState *s = opaque;
+
+    s->rtc_mode = 0xff;
+    s->rtc_reg = 0;
+    s->rtc_cmd = 0;
+    s->rtc_irq_mode = 2;
+
+    s->sys_portc = 0xff;//b8;
+    s->sys_portc_patch = 8;
+    s->prn_porta = 0xff;
+    s->prn_portc = 0x81;
+}
+
+static const VMStateDescription vmstate_sysport = {
+    .name = "pc98-sys",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .minimum_version_id_old = 1,
+    .fields      = (VMStateField []) {
+        VMSTATE_UINT8(rtc_reg, SysPortState),
+        VMSTATE_UINT8(rtc_cmd, SysPortState),
+        VMSTATE_UINT64(rtc_shift_out, SysPortState),
+        VMSTATE_UINT8(rtc_shift_cmd, SysPortState),
+        VMSTATE_UINT8(rtc_irq_mode, SysPortState),
+        VMSTATE_UINT8(rtc_irq_count, SysPortState),
+        VMSTATE_UINT8(sys_portc, SysPortState),
+        VMSTATE_UINT8(prn_porta, SysPortState),
+        VMSTATE_UINT8(prn_portc, SysPortState),
+        VMSTATE_UINT8_ARRAY(sdip, SysPortState, 24),
+        VMSTATE_UINT8(sdip_bank, SysPortState),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+static const uint8_t sdip_default[] = {
+#ifdef PC98_DONT_USE_16MB_MEM
+    0x7c, 0x12, 0xf7, 0x3e, 0x7c, 0x7f, 0xff, 0xbf, 0x7f, 0x7f, 0x49, 0x19,
+#else
+    0x7c, 0x12, 0xf7, 0x3e, 0x7c, 0x7f, 0xff, 0xbf, 0x7f, 0x7f, 0x49, 0x98,
+#endif
+    0x8f, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
+};
+
+static int pc98_sys_initfn(ISADevice *dev)
+{
+    ISASysPortState *isa = DO_UPCAST(ISASysPortState, dev, dev);
+    SysPortState *s = &isa->state;
+    char *filename;
+    int i;
+
+    filename = qemu_find_file(QEMU_FILE_TYPE_BIOS, "pc98sdip.bin");
+    if (filename) {
+        load_image(filename, s->sdip);
+        qemu_free(filename);
+    } else {
+        memcpy(s->sdip, sdip_default, 24);
+    }
+    s->sdip_bank = 0;
+
+    register_ioport_write(0x20, 1, 1, rtc_reg_write, s);
+    register_ioport_write(0x22, 1, 1, rtc_mode_write, s);
+    register_ioport_read(0x22, 1, 1, rtc_mode_read, s);
+    register_ioport_write(0x128, 1, 1, rtc_irq_mode_write, s);
+    register_ioport_read(0x128, 1, 1, rtc_irq_mode_read, s);
+
+    register_ioport_read(0x31, 1, 1, sys_porta_read, s);
+    register_ioport_read(0x33, 1, 1, sys_portb_read, s);
+    register_ioport_write(0x35, 1, 1, sys_portc_write, s);
+    register_ioport_read(0x35, 1, 1, sys_portc_read, s);
+    register_ioport_write(0x37, 1, 1, sys_ctrl_write, s);
+
+    register_ioport_write(0x40, 1, 1, prn_porta_write, s);
+    register_ioport_read(0x40, 1, 1, prn_porta_read, s);
+    register_ioport_read(0x42, 1, 1, prn_portb_read, s);
+    register_ioport_write(0x44, 1, 1, prn_portc_write, s);
+    register_ioport_read(0x44, 1, 1, prn_portc_read, s);
+    register_ioport_write(0x46, 1, 1, prn_ctrl_write, s);
+
+    register_ioport_read(0x5c, 2, 2, tstmp_read, s);
+    register_ioport_read(0x5e, 2, 2, tstmp_read, s);
+
+    for (i = 0; i < 12; i++) {
+        register_ioport_write(0x841e + i * 0x100, 1, 1, sdip_data_write, s);
+        register_ioport_read(0x841e + i * 0x100, 1, 1, sdip_data_read, s);
+    }
+    register_ioport_write(0x8f1f, 1, 1, sdip_bank_write, s);
+    register_ioport_write(0xf0f6, 1, 1, sdip_bank_write, s);
+
+    isa_init_irq(dev, &s->irq, isa->isairq);
+
+    s->rtc_timer = qemu_new_timer(rt_clock, rtc_timer_handler, s);
+    qemu_mod_timer(s->rtc_timer, qemu_get_clock(rt_clock) +
+                   rtc_period[(rtc_period_ptr++) & 7]);
+    s->tstmp_initial_clock = qemu_get_clock(vm_clock);
+
+    vmstate_register(-1, &vmstate_sysport, s);
+    pc98_sys_reset(s);
+    qemu_register_reset(pc98_sys_reset, s);
+
+    return 0;
+}
+
+void *pc98_sys_init(void)
+{
+    ISADevice *dev;
+    ISASysPortState *isa;
+
+    dev = isa_create("pc98-sys");
+    qdev_init_nofail(&dev->qdev);
+
+    isa = DO_UPCAST(ISASysPortState, dev, dev);
+    return &isa->state;
+}
+
+static ISADeviceInfo pc98_sys_info = {
+    .qdev.name  = "pc98-sys",
+    .qdev.size  = sizeof(ISASysPortState),
+    .init       = pc98_sys_initfn,
+    .qdev.props = (Property[]) {
+        DEFINE_PROP_UINT32("irq", ISASysPortState, isairq, 15),
+        DEFINE_PROP_END_OF_LIST(),
+    },
+};
+
+static void pc98_sys_register_devices(void)
+{
+    isa_qdev_register(&pc98_sys_info);
+}
+
+device_init(pc98_sys_register_devices)
