diff mbox series

[v2,07/20] audio: add Apple Sound Chip (ASC) emulation

Message ID 20230909094827.33871-8-mark.cave-ayland@ilande.co.uk
State New
Headers show
Series q800: add support for booting MacOS Classic - part 2 | expand

Commit Message

Mark Cave-Ayland Sept. 9, 2023, 9:48 a.m. UTC
The Apple Sound Chip was primarily used by the Macintosh II to generate sound
in hardware which was previously handled by the toolbox ROM with software
interrupts.

Implement both the standard ASC and also the enhanced ASC (EASC) functionality
which is used in the Quadra 800.

Note that whilst real ASC hardware uses AUDIO_FORMAT_S8, this implementation uses
AUDIO_FORMAT_U8 instead because AUDIO_FORMAT_S8 is rarely used and not supported
by some audio backends like PulseAudio and DirectSound when played directly with
-audiodev out.mixing-engine=off.

Co-developed-by: Laurent Vivier <laurent@vivier.eu>
Co-developed-by: Volker Rümelin <vr_qemu@t-online.de>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
---
 MAINTAINERS            |   2 +
 hw/audio/Kconfig       |   3 +
 hw/audio/asc.c         | 699 +++++++++++++++++++++++++++++++++++++++++
 hw/audio/meson.build   |   1 +
 hw/audio/trace-events  |  10 +
 hw/m68k/Kconfig        |   1 +
 include/hw/audio/asc.h |  84 +++++
 7 files changed, 800 insertions(+)
 create mode 100644 hw/audio/asc.c
 create mode 100644 include/hw/audio/asc.h

Comments

Volker Rümelin Sept. 14, 2023, 7:06 a.m. UTC | #1
Am 09.09.23 um 11:48 schrieb Mark Cave-Ayland:
> The Apple Sound Chip was primarily used by the Macintosh II to generate sound
> in hardware which was previously handled by the toolbox ROM with software
> interrupts.
>
> Implement both the standard ASC and also the enhanced ASC (EASC) functionality
> which is used in the Quadra 800.
>
> Note that whilst real ASC hardware uses AUDIO_FORMAT_S8, this implementation uses
> AUDIO_FORMAT_U8 instead because AUDIO_FORMAT_S8 is rarely used and not supported
> by some audio backends like PulseAudio and DirectSound when played directly with
> -audiodev out.mixing-engine=off.
>
> Co-developed-by: Laurent Vivier <laurent@vivier.eu>
> Co-developed-by: Volker Rümelin <vr_qemu@t-online.de>
> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> ---
>  MAINTAINERS            |   2 +
>  hw/audio/Kconfig       |   3 +
>  hw/audio/asc.c         | 699 +++++++++++++++++++++++++++++++++++++++++
>  hw/audio/meson.build   |   1 +
>  hw/audio/trace-events  |  10 +
>  hw/m68k/Kconfig        |   1 +
>  include/hw/audio/asc.h |  84 +++++
>  7 files changed, 800 insertions(+)
>  create mode 100644 hw/audio/asc.c
>  create mode 100644 include/hw/audio/asc.h

Hi Mark,

the function generate_fifo() has four issues. Only the first one
is noticeable.

1. The calculation of the variable limit assumes generate_fifo()
generates one output sample from every input byte. This is correct
for the raw mode, but not for the CD-XA BRR mode. This mode
generates 28 output samples from 15 input bytes. This is the
reason for the stuttering end of a CD-XA BRR mode sound. Every
generate_fifo() call generates approximately only half of the
possible samples when the fifo bytes are running low.

2. generate_fifo() doesn't generate the last output sample from
a CD-XA BRR mode sound. The last sample is generated from internal
state and the code will not be called without at least one byte
in the fifo.

3. It's not necessary to wait for a complete 15 byte packet in
CD-XA BRR mode. Audio playback devices should write all
requested samples immediately if possible.

4. The saturation function in CD-XA BRR mode works with 16 bit
integers. It should saturate at +32767 and -32768.

Since I think a few lines of code explain the issues better
than my words, I've attached a patch below.

With best regards,
Volker

> +static int generate_fifo(ASCState *s, int maxsamples)
> +{
> +    int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
> +    uint8_t *buf = s->mixbuf;
> +    int i, limit, count = 0;
> +
> +    limit = MIN(MAX(s->fifos[0].cnt, s->fifos[1].cnt), maxsamples);
> +    while (count < limit) {
> +        uint8_t val;
> +        int16_t d, f0, f1;
> +        int32_t t;
> +        int shift, filter;
> +        bool hasdata = true;
> +
> +        for (i = 0; i < 2; i++) {
> +            ASCFIFOState *fs = &s->fifos[i];
> +
> +            switch (fs->extregs[ASC_EXTREGS_FIFOCTRL] & 0x83) {
> +            case 0x82:
> +                /*
> +                 * CD-XA BRR mode: exit if there isn't enough data in the FIFO
> +                 * for a complete 15 byte packet
> +                 */
> +                if (fs->xa_cnt == -1 && fs->cnt < 15) {
> +                    hasdata = false;
> +                    continue;
> +                }
> +
> +                if (fs->xa_cnt == -1) {
> +                    /* Start of packet, get flags */
> +                    fs->xa_flags = asc_fifo_get(fs);
> +                    fs->xa_cnt = 0;
> +                }
> +
> +                shift = fs->xa_flags & 0xf;
> +                filter = fs->xa_flags >> 4;
> +                f0 = (int8_t)fs->extregs[ASC_EXTREGS_CDXA_DECOMP_FILT +
> +                                 (filter << 1) + 1];
> +                f1 = (int8_t)fs->extregs[ASC_EXTREGS_CDXA_DECOMP_FILT +
> +                                 (filter << 1)];
> +                if ((fs->xa_cnt & 1) == 0) {
> +                    fs->xa_val = asc_fifo_get(fs);
> +                    d = (fs->xa_val & 0xf) << 12;
> +                } else {
> +                    d = (fs->xa_val & 0xf0) << 8;
> +                }
> +                t = (d >> shift) + (((fs->xa_last[0] * f0) +
> +                                     (fs->xa_last[1] * f1) + 32) >> 6);
> +                if (t < -32768) {
> +                    t = -32768;
> +                } else if (t > 32768) {
> +                    t = 32768;
> +                }
> +
> +                /*
> +                 * CD-XA BRR generates 16-bit signed output, so convert to
> +                 * 8-bit before writing to buffer. Does real hardware do the
> +                 * same?
> +                 */
> +                buf[count * 2 + i] = (uint8_t)(t / 256) ^ 0x80;
> +                fs->xa_cnt++;
> +
> +                fs->xa_last[1] = fs->xa_last[0];
> +                fs->xa_last[0] = (int16_t)t;
> +
> +                if (fs->xa_cnt == 28) {
> +                    /* End of packet */
> +                    fs->xa_cnt = -1;
> +                }
> +                break;
> +
> +            default:
> +                /* fallthrough */
> +            case 0x80:
> +                /* Raw mode */
> +                if (fs->cnt) {
> +                    val = asc_fifo_get(fs);
> +                } else {
> +                    val = 0x80;
> +                }
> +
> +                buf[count * 2 + i] = val;
> +                break;
> +            }
> +        }
> +
> +        if (!hasdata) {
> +            break;
> +        }
> +
> +        count++;
> +    }
> +
> +    /*
> +     * MacOS (un)helpfully leaves the FIFO engine running even when it has
> +     * finished writing out samples, but still expects the FIFO empty
> +     * interrupts to be generated for each FIFO cycle (without these interrupts
> +     * MacOS will freeze)
> +     */
> +    if (s->fifos[0].cnt == 0 && s->fifos[1].cnt == 0) {
> +        if (!s->fifo_empty_ns) {
> +            /* FIFO has completed first empty cycle */
> +            s->fifo_empty_ns = now;
> +        } else if (now > (s->fifo_empty_ns + ASC_FIFO_CYCLE_TIME)) {
> +            /* FIFO has completed entire cycle with no data */
> +            s->fifos[0].int_status |= ASC_FIFO_STATUS_HALF_FULL |
> +                                      ASC_FIFO_STATUS_FULL_EMPTY;
> +            s->fifos[1].int_status |= ASC_FIFO_STATUS_HALF_FULL |
> +                                      ASC_FIFO_STATUS_FULL_EMPTY;
> +            s->fifo_empty_ns = now;
> +            asc_raise_irq(s);
> +        }
> +    } else {
> +        /* FIFO contains data, reset empty time */
> +        s->fifo_empty_ns = 0;
> +    }
> +
> +    return count;
> +}
>

diff --git a/hw/audio/asc.c b/hw/audio/asc.c
index b01b285512..74988fef9c 100644
--- a/hw/audio/asc.c
+++ b/hw/audio/asc.c
@@ -155,31 +155,26 @@ static int generate_fifo(ASCState *s, int maxsamples)
 {
     int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
     uint8_t *buf = s->mixbuf;
-    int i, limit, count = 0;
+    int i, wcount = 0;
 
-    limit = MIN(MAX(s->fifos[0].cnt, s->fifos[1].cnt), maxsamples);
-    while (count < limit) {
+    while (wcount < maxsamples) {
         uint8_t val;
         int16_t d, f0, f1;
         int32_t t;
         int shift, filter;
-        bool hasdata = true;
+        bool hasdata = false;
 
         for (i = 0; i < 2; i++) {
             ASCFIFOState *fs = &s->fifos[i];
 
             switch (fs->extregs[ASC_EXTREGS_FIFOCTRL] & 0x83) {
             case 0x82:
-                /*
-                 * CD-XA BRR mode: exit if there isn't enough data in
the FIFO
-                 * for a complete 15 byte packet
-                 */
-                if (fs->xa_cnt == -1 && fs->cnt < 15) {
-                    hasdata = false;
-                    continue;
-                }
-
+                /* CD-XA BRR mode: decompress 15 bytes into 28 16bit
samples */
                 if (fs->xa_cnt == -1) {
+                    if (!fs->cnt) {
+                        val = 0x80;
+                        break;
+                    }
                     /* Start of packet, get flags */
                     fs->xa_flags = asc_fifo_get(fs);
                     fs->xa_cnt = 0;
@@ -192,6 +187,10 @@ static int generate_fifo(ASCState *s, int maxsamples)
                 f1 = (int8_t)fs->extregs[ASC_EXTREGS_CDXA_DECOMP_FILT +
                                  (filter << 1)];
                 if ((fs->xa_cnt & 1) == 0) {
+                    if (!fs->cnt) {
+                        val = 0x80;
+                        break;
+                    }
                     fs->xa_val = asc_fifo_get(fs);
                     d = (fs->xa_val & 0xf) << 12;
                 } else {
@@ -201,8 +200,8 @@ static int generate_fifo(ASCState *s, int maxsamples)
                                      (fs->xa_last[1] * f1) + 32) >> 6);
                 if (t < -32768) {
                     t = -32768;
-                } else if (t > 32768) {
-                    t = 32768;
+                } else if (t > 32767) {
+                    t = 32767;
                 }
 
                 /*
@@ -210,7 +209,8 @@ static int generate_fifo(ASCState *s, int maxsamples)
                  * 8-bit before writing to buffer. Does real hardware
do the
                  * same?
                  */
-                buf[count * 2 + i] = (uint8_t)(t / 256) ^ 0x80;
+                val = (uint8_t)(t / 256) ^ 0x80;
+                hasdata = true;
                 fs->xa_cnt++;
 
                 fs->xa_last[1] = fs->xa_last[0];
@@ -228,20 +228,21 @@ static int generate_fifo(ASCState *s, int maxsamples)
                 /* Raw mode */
                 if (fs->cnt) {
                     val = asc_fifo_get(fs);
+                    hasdata = true;
                 } else {
                     val = 0x80;
                 }
-
-                buf[count * 2 + i] = val;
                 break;
             }
+
+            buf[wcount * 2 + i] = val;
         }
 
         if (!hasdata) {
             break;
         }
 
-        count++;
+        wcount++;
     }
 
     /*
@@ -268,7 +269,7 @@ static int generate_fifo(ASCState *s, int maxsamples)
         s->fifo_empty_ns = 0;
     }
 
-    return count;
+    return wcount;
 }
 
 static int generate_wavetable(ASCState *s, int maxsamples)
Mark Cave-Ayland Sept. 20, 2023, 3:39 p.m. UTC | #2
On 14/09/2023 08:06, Volker Rümelin wrote:

> Am 09.09.23 um 11:48 schrieb Mark Cave-Ayland:
>> The Apple Sound Chip was primarily used by the Macintosh II to generate sound
>> in hardware which was previously handled by the toolbox ROM with software
>> interrupts.
>>
>> Implement both the standard ASC and also the enhanced ASC (EASC) functionality
>> which is used in the Quadra 800.
>>
>> Note that whilst real ASC hardware uses AUDIO_FORMAT_S8, this implementation uses
>> AUDIO_FORMAT_U8 instead because AUDIO_FORMAT_S8 is rarely used and not supported
>> by some audio backends like PulseAudio and DirectSound when played directly with
>> -audiodev out.mixing-engine=off.
>>
>> Co-developed-by: Laurent Vivier <laurent@vivier.eu>
>> Co-developed-by: Volker Rümelin <vr_qemu@t-online.de>
>> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
>> ---
>>   MAINTAINERS            |   2 +
>>   hw/audio/Kconfig       |   3 +
>>   hw/audio/asc.c         | 699 +++++++++++++++++++++++++++++++++++++++++
>>   hw/audio/meson.build   |   1 +
>>   hw/audio/trace-events  |  10 +
>>   hw/m68k/Kconfig        |   1 +
>>   include/hw/audio/asc.h |  84 +++++
>>   7 files changed, 800 insertions(+)
>>   create mode 100644 hw/audio/asc.c
>>   create mode 100644 include/hw/audio/asc.h
> 
> Hi Mark,
> 
> the function generate_fifo() has four issues. Only the first one
> is noticeable.
> 
> 1. The calculation of the variable limit assumes generate_fifo()
> generates one output sample from every input byte. This is correct
> for the raw mode, but not for the CD-XA BRR mode. This mode
> generates 28 output samples from 15 input bytes. This is the
> reason for the stuttering end of a CD-XA BRR mode sound. Every
> generate_fifo() call generates approximately only half of the
> possible samples when the fifo bytes are running low.
> 
> 2. generate_fifo() doesn't generate the last output sample from
> a CD-XA BRR mode sound. The last sample is generated from internal
> state and the code will not be called without at least one byte
> in the fifo.
> 
> 3. It's not necessary to wait for a complete 15 byte packet in
> CD-XA BRR mode. Audio playback devices should write all
> requested samples immediately if possible.
> 
> 4. The saturation function in CD-XA BRR mode works with 16 bit
> integers. It should saturate at +32767 and -32768.
> 
> Since I think a few lines of code explain the issues better
> than my words, I've attached a patch below.
> 
> With best regards,
> Volker

Hi Volker,

Thanks for detailed explanation above - everything makes sense based upon previous 
discussions. My only question is in comment 3 where you say "Audio playback devices 
should write all requested samples immediately if possible": can you clarify does 
this mean that the supplied length to the audio callback represents a *required* 
rather than a *maximum* number of samples?

Regardless of this I've had some time to test on Windows this afternoon, and I can 
confirm that your changes fix the outstanding audio issues. I've squashed your 
changes locally and I'll included them in the next revision of the series, although 
I'll likely wait a bit first to see if any more reviews are forthcoming.


Many thanks,

Mark.
Volker Rümelin Sept. 23, 2023, 7:09 a.m. UTC | #3
Am 20.09.23 um 17:39 schrieb Mark Cave-Ayland:
> On 14/09/2023 08:06, Volker Rümelin wrote:
>
>> Am 09.09.23 um 11:48 schrieb Mark Cave-Ayland:
>>> The Apple Sound Chip was primarily used by the Macintosh II to
>>> generate sound
>>> in hardware which was previously handled by the toolbox ROM with
>>> software
>>> interrupts.
>>>
>>> Implement both the standard ASC and also the enhanced ASC (EASC)
>>> functionality
>>> which is used in the Quadra 800.
>>>
>>> Note that whilst real ASC hardware uses AUDIO_FORMAT_S8, this
>>> implementation uses
>>> AUDIO_FORMAT_U8 instead because AUDIO_FORMAT_S8 is rarely used and
>>> not supported
>>> by some audio backends like PulseAudio and DirectSound when played
>>> directly with
>>> -audiodev out.mixing-engine=off.
>>>
>>> Co-developed-by: Laurent Vivier <laurent@vivier.eu>
>>> Co-developed-by: Volker Rümelin <vr_qemu@t-online.de>
>>> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
>>> ---
>>>   MAINTAINERS            |   2 +
>>>   hw/audio/Kconfig       |   3 +
>>>   hw/audio/asc.c         | 699
>>> +++++++++++++++++++++++++++++++++++++++++
>>>   hw/audio/meson.build   |   1 +
>>>   hw/audio/trace-events  |  10 +
>>>   hw/m68k/Kconfig        |   1 +
>>>   include/hw/audio/asc.h |  84 +++++
>>>   7 files changed, 800 insertions(+)
>>>   create mode 100644 hw/audio/asc.c
>>>   create mode 100644 include/hw/audio/asc.h
>>
>> Hi Mark,
>>
>> the function generate_fifo() has four issues. Only the first one
>> is noticeable.
>>
>> 1. The calculation of the variable limit assumes generate_fifo()
>> generates one output sample from every input byte. This is correct
>> for the raw mode, but not for the CD-XA BRR mode. This mode
>> generates 28 output samples from 15 input bytes. This is the
>> reason for the stuttering end of a CD-XA BRR mode sound. Every
>> generate_fifo() call generates approximately only half of the
>> possible samples when the fifo bytes are running low.
>>
>> 2. generate_fifo() doesn't generate the last output sample from
>> a CD-XA BRR mode sound. The last sample is generated from internal
>> state and the code will not be called without at least one byte
>> in the fifo.
>>
>> 3. It's not necessary to wait for a complete 15 byte packet in
>> CD-XA BRR mode. Audio playback devices should write all
>> requested samples immediately if possible.
>>
>> 4. The saturation function in CD-XA BRR mode works with 16 bit
>> integers. It should saturate at +32767 and -32768.
>>
>> Since I think a few lines of code explain the issues better
>> than my words, I've attached a patch below.
>>
>> With best regards,
>> Volker
>
> Hi Volker,
>
> Thanks for detailed explanation above - everything makes sense based
> upon previous discussions. My only question is in comment 3 where you
> say "Audio playback devices should write all requested samples
> immediately if possible": can you clarify does this mean that the
> supplied length to the audio callback represents a *required* rather
> than a *maximum* number of samples?
>

Hi Mark,

the supplied length is the number of bytes needed to fill the downstream
audio buffer completely or as fast as possible. An incompletely filled
buffer increases the probability of dropouts. The supplied length is
also the maximum number of bytes AUD_write() will write.

So it's better to write as many bytes as possible, but if you can't it
won't cause audio problems immediately in most cases.

With best regards,
Volker

> Regardless of this I've had some time to test on Windows this
> afternoon, and I can confirm that your changes fix the outstanding
> audio issues. I've squashed your changes locally and I'll included
> them in the next revision of the series, although I'll likely wait a
> bit first to see if any more reviews are forthcoming.
>
>
> Many thanks,
>
> Mark.
>
diff mbox series

Patch

diff --git a/MAINTAINERS b/MAINTAINERS
index e02c0073af..902b575451 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1223,6 +1223,7 @@  F: hw/display/macfb.c
 F: hw/block/swim.c
 F: hw/misc/djmemc.c
 F: hw/misc/iosb.c
+F: hw/audio/asc.c
 F: hw/m68k/bootinfo.h
 F: include/standard-headers/asm-m68k/bootinfo.h
 F: include/standard-headers/asm-m68k/bootinfo-mac.h
@@ -1234,6 +1235,7 @@  F: include/hw/m68k/q800.h
 F: include/hw/m68k/q800-glue.h
 F: include/hw/misc/djmemc.h
 F: include/hw/misc/iosb.h
+F: include/hw/audio/asc.h
 
 virt
 M: Laurent Vivier <laurent@vivier.eu>
diff --git a/hw/audio/Kconfig b/hw/audio/Kconfig
index e76c69ca7e..d0993514a1 100644
--- a/hw/audio/Kconfig
+++ b/hw/audio/Kconfig
@@ -47,3 +47,6 @@  config PL041
 
 config CS4231
     bool
+
+config ASC
+    bool
diff --git a/hw/audio/asc.c b/hw/audio/asc.c
new file mode 100644
index 0000000000..336ace0cd6
--- /dev/null
+++ b/hw/audio/asc.c
@@ -0,0 +1,699 @@ 
+/*
+ * QEMU Apple Sound Chip emulation
+ *
+ * Apple Sound Chip (ASC) 344S0063
+ * Enhanced Apple Sound Chip (EASC) 343S1063
+ *
+ * Copyright (c) 2012-2018 Laurent Vivier <laurent@vivier.eu>
+ * Copyright (c) 2022 Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/timer.h"
+#include "hw/sysbus.h"
+#include "hw/irq.h"
+#include "audio/audio.h"
+#include "hw/audio/asc.h"
+#include "hw/qdev-properties.h"
+#include "migration/vmstate.h"
+#include "trace.h"
+
+/*
+ * Linux doesn't provide information about ASC, see arch/m68k/mac/macboing.c
+ * and arch/m68k/include/asm/mac_asc.h
+ *
+ * best information is coming from MAME:
+ *   https://github.com/mamedev/mame/blob/master/src/devices/sound/asc.h
+ *   https://github.com/mamedev/mame/blob/master/src/devices/sound/asc.cpp
+ *   Emulation by R. Belmont
+ * or MESS:
+ *   http://mess.redump.net/mess/driver_info/easc
+ *
+ *     0x800: VERSION
+ *     0x801: MODE
+ *            1=FIFO mode,
+ *            2=wavetable mode
+ *     0x802: CONTROL
+ *            bit 0=analog or PWM output,
+ *                1=stereo/mono,
+ *                7=processing time exceeded
+ *     0x803: FIFO MODE
+ *            bit 7=clear FIFO,
+ *            bit 1="non-ROM companding",
+ *            bit 0="ROM companding")
+ *     0x804: FIFO IRQ STATUS
+ *            bit 0=ch A 1/2 full,
+ *                1=ch A full,
+ *                2=ch B 1/2 full,
+ *                3=ch B full)
+ *     0x805: WAVETABLE CONTROL
+ *            bits 0-3 wavetables 0-3 start
+ *     0x806: VOLUME
+ *            bits 2-4 = 3 bit internal ASC volume,
+ *            bits 5-7 = volume control sent to Sony sound chip
+ *     0x807: CLOCK RATE
+ *            0 = Mac 22257 Hz,
+ *            1 = undefined,
+ *            2 = 22050 Hz,
+ *            3 = 44100 Hz
+ *     0x80a: PLAY REC A
+ *     0x80f: TEST
+ *            bits 6-7 = digital test,
+ *            bits 4-5 = analog test
+ *     0x810: WAVETABLE 0 PHASE
+ *            big-endian 9.15 fixed-point, only 24 bits valid
+ *     0x814: WAVETABLE 0 INCREMENT
+ *            big-endian 9.15 fixed-point, only 24 bits valid
+ *     0x818: WAVETABLE 1 PHASE
+ *     0x81C: WAVETABLE 1 INCREMENT
+ *     0x820: WAVETABLE 2 PHASE
+ *     0x824: WAVETABLE 2 INCREMENT
+ *     0x828: WAVETABLE 3 PHASE
+ *     0x82C: WAVETABLE 3 INCREMENT
+ *     0x830: UNKNOWN START
+ *            NetBSD writes Wavetable data here (are there more
+ *            wavetables/channels than we know about?)
+ *     0x857: UNKNOWN END
+ */
+
+#define ASC_SIZE           0x2000
+
+enum {
+    ASC_VERSION     = 0x00,
+    ASC_MODE        = 0x01,
+    ASC_CONTROL     = 0x02,
+    ASC_FIFOMODE    = 0x03,
+    ASC_FIFOIRQ     = 0x04,
+    ASC_WAVECTRL    = 0x05,
+    ASC_VOLUME      = 0x06,
+    ASC_CLOCK       = 0x07,
+    ASC_PLAYRECA    = 0x0a,
+    ASC_TEST        = 0x0f,
+    ASC_WAVETABLE   = 0x10
+};
+
+#define ASC_FIFO_STATUS_HALF_FULL      1
+#define ASC_FIFO_STATUS_FULL_EMPTY     2
+
+#define ASC_EXTREGS_FIFOCTRL           0x8
+#define ASC_EXTREGS_INTCTRL            0x9
+#define ASC_EXTREGS_CDXA_DECOMP_FILT   0x10
+
+#define ASC_FIFO_CYCLE_TIME            ((NANOSECONDS_PER_SECOND / ASC_FREQ) * \
+                                        0x400)
+
+static void asc_raise_irq(ASCState *s)
+{
+    qemu_set_irq(s->irq, 1);
+}
+
+static void asc_lower_irq(ASCState *s)
+{
+    qemu_set_irq(s->irq, 0);
+}
+
+static uint8_t asc_fifo_get(ASCFIFOState *fs)
+{
+    ASCState *s = container_of(fs, ASCState, fifos[fs->index]);
+    bool fifo_half_irq_enabled = fs->extregs[ASC_EXTREGS_INTCTRL] & 1;
+    uint8_t val;
+
+    assert(fs->cnt);
+
+    val = fs->fifo[fs->rptr];
+    trace_asc_fifo_get('A' + fs->index, fs->rptr, fs->cnt, val);
+
+    fs->rptr++;
+    fs->rptr &= 0x3ff;
+    fs->cnt--;
+
+    if (fs->cnt <= 0x1ff) {
+        /* FIFO less than half full */
+        fs->int_status |= ASC_FIFO_STATUS_HALF_FULL;
+    } else {
+        /* FIFO more than half full */
+        fs->int_status &= ~ASC_FIFO_STATUS_HALF_FULL;
+    }
+
+    if (fs->cnt == 0x1ff && fifo_half_irq_enabled) {
+        /* Raise FIFO half full IRQ */
+        asc_raise_irq(s);
+    }
+
+    if (fs->cnt == 0) {
+        /* Raise FIFO empty IRQ */
+        fs->int_status |= ASC_FIFO_STATUS_FULL_EMPTY;
+        asc_raise_irq(s);
+    }
+
+    return val;
+}
+
+static int generate_fifo(ASCState *s, int maxsamples)
+{
+    int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+    uint8_t *buf = s->mixbuf;
+    int i, limit, count = 0;
+
+    limit = MIN(MAX(s->fifos[0].cnt, s->fifos[1].cnt), maxsamples);
+    while (count < limit) {
+        uint8_t val;
+        int16_t d, f0, f1;
+        int32_t t;
+        int shift, filter;
+        bool hasdata = true;
+
+        for (i = 0; i < 2; i++) {
+            ASCFIFOState *fs = &s->fifos[i];
+
+            switch (fs->extregs[ASC_EXTREGS_FIFOCTRL] & 0x83) {
+            case 0x82:
+                /*
+                 * CD-XA BRR mode: exit if there isn't enough data in the FIFO
+                 * for a complete 15 byte packet
+                 */
+                if (fs->xa_cnt == -1 && fs->cnt < 15) {
+                    hasdata = false;
+                    continue;
+                }
+
+                if (fs->xa_cnt == -1) {
+                    /* Start of packet, get flags */
+                    fs->xa_flags = asc_fifo_get(fs);
+                    fs->xa_cnt = 0;
+                }
+
+                shift = fs->xa_flags & 0xf;
+                filter = fs->xa_flags >> 4;
+                f0 = (int8_t)fs->extregs[ASC_EXTREGS_CDXA_DECOMP_FILT +
+                                 (filter << 1) + 1];
+                f1 = (int8_t)fs->extregs[ASC_EXTREGS_CDXA_DECOMP_FILT +
+                                 (filter << 1)];
+                if ((fs->xa_cnt & 1) == 0) {
+                    fs->xa_val = asc_fifo_get(fs);
+                    d = (fs->xa_val & 0xf) << 12;
+                } else {
+                    d = (fs->xa_val & 0xf0) << 8;
+                }
+                t = (d >> shift) + (((fs->xa_last[0] * f0) +
+                                     (fs->xa_last[1] * f1) + 32) >> 6);
+                if (t < -32768) {
+                    t = -32768;
+                } else if (t > 32768) {
+                    t = 32768;
+                }
+
+                /*
+                 * CD-XA BRR generates 16-bit signed output, so convert to
+                 * 8-bit before writing to buffer. Does real hardware do the
+                 * same?
+                 */
+                buf[count * 2 + i] = (uint8_t)(t / 256) ^ 0x80;
+                fs->xa_cnt++;
+
+                fs->xa_last[1] = fs->xa_last[0];
+                fs->xa_last[0] = (int16_t)t;
+
+                if (fs->xa_cnt == 28) {
+                    /* End of packet */
+                    fs->xa_cnt = -1;
+                }
+                break;
+
+            default:
+                /* fallthrough */
+            case 0x80:
+                /* Raw mode */
+                if (fs->cnt) {
+                    val = asc_fifo_get(fs);
+                } else {
+                    val = 0x80;
+                }
+
+                buf[count * 2 + i] = val;
+                break;
+            }
+        }
+
+        if (!hasdata) {
+            break;
+        }
+
+        count++;
+    }
+
+    /*
+     * MacOS (un)helpfully leaves the FIFO engine running even when it has
+     * finished writing out samples, but still expects the FIFO empty
+     * interrupts to be generated for each FIFO cycle (without these interrupts
+     * MacOS will freeze)
+     */
+    if (s->fifos[0].cnt == 0 && s->fifos[1].cnt == 0) {
+        if (!s->fifo_empty_ns) {
+            /* FIFO has completed first empty cycle */
+            s->fifo_empty_ns = now;
+        } else if (now > (s->fifo_empty_ns + ASC_FIFO_CYCLE_TIME)) {
+            /* FIFO has completed entire cycle with no data */
+            s->fifos[0].int_status |= ASC_FIFO_STATUS_HALF_FULL |
+                                      ASC_FIFO_STATUS_FULL_EMPTY;
+            s->fifos[1].int_status |= ASC_FIFO_STATUS_HALF_FULL |
+                                      ASC_FIFO_STATUS_FULL_EMPTY;
+            s->fifo_empty_ns = now;
+            asc_raise_irq(s);
+        }
+    } else {
+        /* FIFO contains data, reset empty time */
+        s->fifo_empty_ns = 0;
+    }
+
+    return count;
+}
+
+static int generate_wavetable(ASCState *s, int maxsamples)
+{
+    uint8_t *buf = s->mixbuf;
+    int channel, count = 0;
+
+    while (count < maxsamples) {
+        uint32_t left = 0, right = 0;
+        uint8_t sample;
+
+        for (channel = 0; channel < 4; channel++) {
+            ASCFIFOState *fs = &s->fifos[channel >> 1];
+            int chanreg = ASC_WAVETABLE + (channel << 3);
+            uint32_t phase, incr, offset;
+
+            phase = ldl_be_p(&s->regs[chanreg]);
+            incr = ldl_be_p(&s->regs[chanreg + sizeof(uint32_t)]);
+
+            phase += incr;
+            offset = (phase >> 15) & 0x1ff;
+            sample = fs->fifo[0x200 * (channel >> 1) + offset];
+
+            stl_be_p(&s->regs[chanreg], phase);
+
+            left += sample;
+            right += sample;
+        }
+
+        buf[count * 2] = left >> 2;
+        buf[count * 2 + 1] = right >> 2;
+
+        count++;
+    }
+
+    return count;
+}
+
+static void asc_out_cb(void *opaque, int free_b)
+{
+    ASCState *s = opaque;
+    int samples, generated;
+
+    if (free_b == 0) {
+        return;
+    }
+
+    samples = MIN(s->samples, free_b >> s->shift);
+
+    switch (s->regs[ASC_MODE] & 3) {
+    default:
+        /* Off */
+        generated = 0;
+        break;
+    case 1:
+        /* FIFO mode */
+        generated = generate_fifo(s, samples);
+        break;
+    case 2:
+        /* Wave table mode */
+        generated = generate_wavetable(s, samples);
+        break;
+    }
+
+    if (!generated) {
+        return;
+    }
+
+    AUD_write(s->voice, s->mixbuf, generated << s->shift);
+}
+
+static uint64_t asc_fifo_read(void *opaque, hwaddr addr,
+                              unsigned size)
+{
+    ASCFIFOState *fs = opaque;
+
+    trace_asc_read_fifo('A' + fs->index, addr, size, fs->fifo[addr]);
+    return fs->fifo[addr];
+}
+
+static void asc_fifo_write(void *opaque, hwaddr addr, uint64_t value,
+                           unsigned size)
+{
+    ASCFIFOState *fs = opaque;
+    ASCState *s = container_of(fs, ASCState, fifos[fs->index]);
+    bool fifo_half_irq_enabled = fs->extregs[ASC_EXTREGS_INTCTRL] & 1;
+
+    trace_asc_write_fifo('A' + fs->index, addr, size, fs->wptr, fs->cnt, value);
+
+    if (s->regs[ASC_MODE] == 1) {
+        fs->fifo[fs->wptr++] = value;
+        fs->wptr &= 0x3ff;
+        fs->cnt++;
+
+        if (fs->cnt <= 0x1ff) {
+            /* FIFO less than half full */
+            fs->int_status |= ASC_FIFO_STATUS_HALF_FULL;
+        } else {
+            /* FIFO at least half full */
+            fs->int_status &= ~ASC_FIFO_STATUS_HALF_FULL;
+        }
+
+        if (fs->cnt == 0x200 && fifo_half_irq_enabled) {
+            /* Raise FIFO half full interrupt */
+            asc_raise_irq(s);
+        }
+
+        if (fs->cnt == 0x3ff) {
+            /* Raise FIFO full interrupt */
+            fs->int_status |= ASC_FIFO_STATUS_FULL_EMPTY;
+            asc_raise_irq(s);
+        }
+    } else {
+        fs->fifo[addr] = value;
+    }
+    return;
+}
+
+static const MemoryRegionOps asc_fifo_ops = {
+    .read = asc_fifo_read,
+    .write = asc_fifo_write,
+    .impl = {
+        .min_access_size = 1,
+        .max_access_size = 1,
+    },
+    .endianness = DEVICE_BIG_ENDIAN,
+};
+
+static void asc_fifo_reset(ASCFIFOState *fs);
+
+static uint64_t asc_read(void *opaque, hwaddr addr,
+                         unsigned size)
+{
+    ASCState *s = opaque;
+    uint64_t prev, value;
+
+    switch (addr) {
+    case ASC_VERSION:
+        switch (s->type) {
+        default:
+        case ASC_TYPE_ASC:
+            value = 0;
+            break;
+        case ASC_TYPE_EASC:
+            value = 0xb0;
+            break;
+        }
+        break;
+    case ASC_FIFOIRQ:
+        prev = (s->fifos[0].int_status & 0x3) |
+                (s->fifos[1].int_status & 0x3) << 2;
+
+        s->fifos[0].int_status = 0;
+        s->fifos[1].int_status = 0;
+        asc_lower_irq(s);
+        value = prev;
+        break;
+    default:
+        value = s->regs[addr];
+        break;
+    }
+
+    trace_asc_read_reg(addr, size, value);
+    return value;
+}
+
+static void asc_write(void *opaque, hwaddr addr, uint64_t value,
+                      unsigned size)
+{
+    ASCState *s = opaque;
+
+    switch (addr) {
+    case ASC_MODE:
+        value &= 3;
+        if (value != s->regs[ASC_MODE]) {
+            asc_fifo_reset(&s->fifos[0]);
+            asc_fifo_reset(&s->fifos[1]);
+            asc_lower_irq(s);
+            if (value != 0) {
+                AUD_set_active_out(s->voice, 1);
+            } else {
+                AUD_set_active_out(s->voice, 0);
+            }
+        }
+        break;
+    case ASC_FIFOMODE:
+        if (value & 0x80) {
+            asc_fifo_reset(&s->fifos[0]);
+            asc_fifo_reset(&s->fifos[1]);
+            asc_lower_irq(s);
+        }
+        break;
+    case ASC_WAVECTRL:
+        break;
+    case ASC_VOLUME:
+        {
+            int vol = (value & 0xe0);
+
+            AUD_set_volume_out(s->voice, 0, vol, vol);
+            break;
+        }
+    }
+
+    trace_asc_write_reg(addr, size, value);
+    s->regs[addr] = value;
+}
+
+static const MemoryRegionOps asc_regs_ops = {
+    .read = asc_read,
+    .write = asc_write,
+    .endianness = DEVICE_BIG_ENDIAN,
+    .impl = {
+        .min_access_size = 1,
+        .max_access_size = 1,
+    }
+};
+
+static uint64_t asc_ext_read(void *opaque, hwaddr addr,
+                             unsigned size)
+{
+    ASCFIFOState *fs = opaque;
+    uint64_t value;
+
+    value = fs->extregs[addr];
+
+    trace_asc_read_extreg('A' + fs->index, addr, size, value);
+    return value;
+}
+
+static void asc_ext_write(void *opaque, hwaddr addr, uint64_t value,
+                          unsigned size)
+{
+    ASCFIFOState *fs = opaque;
+
+    trace_asc_write_extreg('A' + fs->index, addr, size, value);
+
+    fs->extregs[addr] = value;
+}
+
+static const MemoryRegionOps asc_extregs_ops = {
+    .read = asc_ext_read,
+    .write = asc_ext_write,
+    .impl = {
+        .min_access_size = 1,
+        .max_access_size = 1,
+    },
+    .endianness = DEVICE_BIG_ENDIAN,
+};
+
+static int asc_post_load(void *opaque, int version)
+{
+    ASCState *s = ASC(opaque);
+
+    if (s->regs[ASC_MODE] != 0) {
+        AUD_set_active_out(s->voice, 1);
+    }
+
+    return 0;
+}
+
+static const VMStateDescription vmstate_asc_fifo = {
+    .name = "apple-sound-chip.fifo",
+    .version_id = 0,
+    .minimum_version_id = 0,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINT8_ARRAY(fifo, ASCFIFOState, ASC_FIFO_SIZE),
+        VMSTATE_UINT8(int_status, ASCFIFOState),
+        VMSTATE_INT32(cnt, ASCFIFOState),
+        VMSTATE_INT32(wptr, ASCFIFOState),
+        VMSTATE_INT32(rptr, ASCFIFOState),
+        VMSTATE_UINT8_ARRAY(extregs, ASCFIFOState, ASC_EXTREG_SIZE),
+        VMSTATE_INT32(xa_cnt, ASCFIFOState),
+        VMSTATE_UINT8(xa_val, ASCFIFOState),
+        VMSTATE_UINT8(xa_flags, ASCFIFOState),
+        VMSTATE_INT16_ARRAY(xa_last, ASCFIFOState, 2),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+static const VMStateDescription vmstate_asc = {
+    .name = "apple-sound-chip",
+    .version_id = 0,
+    .minimum_version_id = 0,
+    .post_load = asc_post_load,
+    .fields = (VMStateField[]) {
+        VMSTATE_STRUCT_ARRAY(fifos, ASCState, 2, 0, vmstate_asc_fifo,
+                             ASCFIFOState),
+        VMSTATE_UINT8_ARRAY(regs, ASCState, ASC_REG_SIZE),
+        VMSTATE_INT64(fifo_empty_ns, ASCState),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+static void asc_fifo_reset(ASCFIFOState *fs)
+{
+    fs->wptr = 0;
+    fs->rptr = 0;
+    fs->cnt = 0;
+    fs->xa_cnt = -1;
+    fs->int_status = 0;
+}
+
+static void asc_fifo_init(ASCFIFOState *fs, int index)
+{
+    ASCState *s = container_of(fs, ASCState, fifos[index]);
+    char *name;
+
+    fs->index = index;
+    name = g_strdup_printf("asc.fifo%c", 'A' + index);
+    memory_region_init_io(&fs->mem_fifo, OBJECT(s), &asc_fifo_ops, fs,
+                          name, ASC_FIFO_SIZE);
+    g_free(name);
+
+    name = g_strdup_printf("asc.extregs%c", 'A' + index);
+    memory_region_init_io(&fs->mem_extregs, OBJECT(s), &asc_extregs_ops,
+                          fs, name, ASC_EXTREG_SIZE);
+    g_free(name);
+}
+
+static void asc_reset_hold(Object *obj)
+{
+    ASCState *s = ASC(obj);
+
+    AUD_set_active_out(s->voice, 0);
+
+    memset(s->regs, 0, sizeof(s->regs));
+    asc_fifo_reset(&s->fifos[0]);
+    asc_fifo_reset(&s->fifos[1]);
+    s->fifo_empty_ns = 0;
+
+    if (s->type == ASC_TYPE_ASC) {
+        /* FIFO half full IRQs enabled by default */
+        s->fifos[0].extregs[ASC_EXTREGS_INTCTRL] = 1;
+        s->fifos[1].extregs[ASC_EXTREGS_INTCTRL] = 1;
+    }
+}
+
+static void asc_unrealize(DeviceState *dev)
+{
+    ASCState *s = ASC(dev);
+
+    g_free(s->mixbuf);
+
+    AUD_remove_card(&s->card);
+}
+
+static void asc_realize(DeviceState *dev, Error **errp)
+{
+    ASCState *s = ASC(dev);
+    struct audsettings as;
+
+    AUD_register_card("Apple Sound Chip", &s->card);
+
+    as.freq = ASC_FREQ;
+    as.nchannels = 2;
+    as.fmt = AUDIO_FORMAT_U8;
+    as.endianness = AUDIO_HOST_ENDIANNESS;
+
+    s->voice = AUD_open_out(&s->card, s->voice, "asc.out", s, asc_out_cb,
+                            &as);
+    s->shift = 1;
+    s->samples = AUD_get_buffer_size_out(s->voice) >> s->shift;
+    s->mixbuf = g_malloc0(s->samples << s->shift);
+
+    /* Add easc registers if required */
+    if (s->type == ASC_TYPE_EASC) {
+        memory_region_add_subregion(&s->asc, ASC_EXTREG_OFFSET,
+                                    &s->fifos[0].mem_extregs);
+        memory_region_add_subregion(&s->asc,
+                                    ASC_EXTREG_OFFSET + ASC_EXTREG_SIZE,
+                                    &s->fifos[1].mem_extregs);
+    }
+}
+
+static void asc_init(Object *obj)
+{
+    ASCState *s = ASC(obj);
+    SysBusDevice *sbd = SYS_BUS_DEVICE(obj);
+
+    memory_region_init(&s->asc, OBJECT(obj), "asc", ASC_SIZE);
+
+    asc_fifo_init(&s->fifos[0], 0);
+    asc_fifo_init(&s->fifos[1], 1);
+
+    memory_region_add_subregion(&s->asc, ASC_FIFO_OFFSET,
+                                &s->fifos[0].mem_fifo);
+    memory_region_add_subregion(&s->asc,
+                                ASC_FIFO_OFFSET + ASC_FIFO_SIZE,
+                                &s->fifos[1].mem_fifo);
+
+    memory_region_init_io(&s->mem_regs, OBJECT(obj), &asc_regs_ops, s,
+                          "asc.regs", ASC_REG_SIZE);
+    memory_region_add_subregion(&s->asc, ASC_REG_OFFSET, &s->mem_regs);
+
+    sysbus_init_irq(sbd, &s->irq);
+    sysbus_init_mmio(sbd, &s->asc);
+}
+
+static Property asc_properties[] = {
+    DEFINE_AUDIO_PROPERTIES(ASCState, card),
+    DEFINE_PROP_UINT8("asctype", ASCState, type, ASC_TYPE_ASC),
+    DEFINE_PROP_END_OF_LIST(),
+};
+
+static void asc_class_init(ObjectClass *oc, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(oc);
+    ResettableClass *rc = RESETTABLE_CLASS(oc);
+
+    dc->realize = asc_realize;
+    dc->unrealize = asc_unrealize;
+    set_bit(DEVICE_CATEGORY_SOUND, dc->categories);
+    dc->vmsd = &vmstate_asc;
+    device_class_set_props(dc, asc_properties);
+    rc->phases.hold = asc_reset_hold;
+}
+
+static const TypeInfo asc_info_types[] = {
+    {
+        .name = TYPE_ASC,
+        .parent = TYPE_SYS_BUS_DEVICE,
+        .instance_size = sizeof(ASCState),
+        .instance_init = asc_init,
+        .class_init = asc_class_init,
+    },
+};
+
+DEFINE_TYPES(asc_info_types)
diff --git a/hw/audio/meson.build b/hw/audio/meson.build
index d0fda1009e..8805322f5c 100644
--- a/hw/audio/meson.build
+++ b/hw/audio/meson.build
@@ -1,6 +1,7 @@ 
 system_ss.add(files('soundhw.c'))
 system_ss.add(when: 'CONFIG_AC97', if_true: files('ac97.c'))
 system_ss.add(when: 'CONFIG_ADLIB', if_true: files('fmopl.c', 'adlib.c'))
+system_ss.add(when: 'CONFIG_ASC', if_true: files('asc.c'))
 system_ss.add(when: 'CONFIG_CS4231', if_true: files('cs4231.c'))
 system_ss.add(when: 'CONFIG_CS4231A', if_true: files('cs4231a.c'))
 system_ss.add(when: 'CONFIG_ES1370', if_true: files('es1370.c'))
diff --git a/hw/audio/trace-events b/hw/audio/trace-events
index 4dec48a4fd..89ef2996e5 100644
--- a/hw/audio/trace-events
+++ b/hw/audio/trace-events
@@ -17,3 +17,13 @@  via_ac97_codec_write(uint8_t addr, uint16_t val) "0x%x <- 0x%x"
 via_ac97_sgd_fetch(uint32_t curr, uint32_t addr, char stop, char eol, char flag, uint32_t len) "curr=0x%x addr=0x%x %c%c%c len=%d"
 via_ac97_sgd_read(uint64_t addr, unsigned size, uint64_t val) "0x%"PRIx64" %d -> 0x%"PRIx64
 via_ac97_sgd_write(uint64_t addr, unsigned size, uint64_t val) "0x%"PRIx64" %d <- 0x%"PRIx64
+
+# asc.c
+asc_read_fifo(const char fifo, int reg, unsigned size, uint64_t value) "fifo %c reg=0x%03x size=%u value=0x%"PRIx64
+asc_read_reg(int reg, unsigned size, uint64_t value) "reg=0x%03x size=%u value=0x%"PRIx64
+asc_read_extreg(const char fifo, int reg, unsigned size, uint64_t value) "fifo %c reg=0x%03x size=%u value=0x%"PRIx64
+asc_fifo_get(const char fifo, int rptr, int cnt, uint64_t value) "fifo %c rptr=0x%x cnt=0x%x value=0x%"PRIx64
+asc_write_fifo(const char fifo, int reg, unsigned size, int wrptr, int cnt, uint64_t value) "fifo %c reg=0x%03x size=%u wptr=0x%x cnt=0x%x value=0x%"PRIx64
+asc_write_reg(int reg, unsigned size, uint64_t value) "reg=0x%03x size=%u value=0x%"PRIx64
+asc_write_extreg(const char fifo, int reg, unsigned size, uint64_t value) "fifo %c reg=0x%03x size=%u value=0x%"PRIx64
+asc_update_irq(int irq, int a, int b) "set IRQ to %d (A: 0x%x B: 0x%x)"
diff --git a/hw/m68k/Kconfig b/hw/m68k/Kconfig
index 64fa70a0db..d88741ec9d 100644
--- a/hw/m68k/Kconfig
+++ b/hw/m68k/Kconfig
@@ -25,6 +25,7 @@  config Q800
     select OR_IRQ
     select DJMEMC
     select IOSB
+    select ASC
 
 config M68K_VIRT
     bool
diff --git a/include/hw/audio/asc.h b/include/hw/audio/asc.h
new file mode 100644
index 0000000000..d9412815c3
--- /dev/null
+++ b/include/hw/audio/asc.h
@@ -0,0 +1,84 @@ 
+/*
+ * QEMU Apple Sound Chip emulation
+ *
+ * Apple Sound Chip (ASC) 344S0063
+ * Enhanced Apple Sound Chip (EASC) 343S1063
+ *
+ * Copyright (c) 2012-2018 Laurent Vivier <laurent@vivier.eu>
+ * Copyright (c) 2022 Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#ifndef HW_AUDIO_ASC_H
+#define HW_AUDIO_ASC_H
+
+#include "qemu/osdep.h"
+#include "hw/sysbus.h"
+#include "audio/audio.h"
+
+#define ASC_FREQ 22257
+
+enum {
+    ASC_TYPE_ASC    = 0,  /* original discrete Apple Sound Chip */
+    ASC_TYPE_EASC   = 1   /* discrete Enhanced Apple Sound Chip */
+};
+
+#define ASC_FIFO_OFFSET    0x0
+#define ASC_FIFO_SIZE      0x400
+
+#define ASC_REG_OFFSET     0x800
+#define ASC_REG_SIZE       0x60
+
+#define ASC_EXTREG_OFFSET  0xf00
+#define ASC_EXTREG_SIZE    0x20
+
+typedef struct ASCFIFOState {
+    int index;
+
+    MemoryRegion mem_fifo;
+    uint8_t fifo[ASC_FIFO_SIZE];
+    uint8_t int_status;
+
+    int cnt;
+    int wptr;
+    int rptr;
+
+    MemoryRegion mem_extregs;
+    uint8_t extregs[ASC_EXTREG_SIZE];
+
+    int xa_cnt;
+    uint8_t xa_val;
+    uint8_t xa_flags;
+    int16_t xa_last[2];
+} ASCFIFOState;
+
+struct ASCState {
+    SysBusDevice parent_obj;
+
+    uint8_t type;
+    MemoryRegion asc;
+    MemoryRegion mem_fifo;
+    MemoryRegion mem_regs;
+    MemoryRegion mem_extregs;
+
+    QEMUSoundCard card;
+    SWVoiceOut *voice;
+    uint8_t *mixbuf;
+    int samples;
+    int shift;
+
+    /* Time when we were last able to generate samples */
+    int64_t fifo_empty_ns;
+
+    qemu_irq irq;
+
+    ASCFIFOState fifos[2];
+
+    uint8_t regs[ASC_REG_SIZE];
+};
+
+#define TYPE_ASC "apple-sound-chip"
+OBJECT_DECLARE_SIMPLE_TYPE(ASCState, ASC)
+
+#endif