Add Mindscape Music Board

Ported from PCem

src/include/86box/snd_mmb.h

@@ -0,0 +1,42 @@
+/*
+ * 86Box    A hypervisor and IBM PC system emulator that specializes in
+ *          running old operating systems and software designed for IBM
+ *          PC systems and compatibles from 1981 through fairly recent
+ *          system designs based on the PCI bus.
+ *
+ *          This file is part of the 86Box distribution.
+ *
+ *          Mindscape Music Board emulation.
+ *
+ * Authors: Roy Baer, <https://pcem-emulator.co.uk/>
+ *          Jasmine Iwanek, <jriwanek@gmail.com>
+ *
+ *          Copyright 2025 Roy Baer.
+ *          Copyright 2025 Jasmine Iwanek.
+ */
+#ifndef _SOUND_SND_MMB_H_
+#define _SOUND_SND_MMB_H_
+
+#define MMB_FREQ FREQ_48000
+
+/* NOTE:
+ * The constant clock rate is a deviation from the real hardware which has
+ * the design flaw that the clock rate is always half the ISA bus clock.
+ */
+#define MMB_CLOCK 2386364
+
+typedef struct ay_3_891x_s {
+    uint8_t index;
+    uint8_t regs[16];
+    struct  ayumi chip;
+} ay_3_891x_t;
+
+typedef struct mmb_s {
+    ay_3_891x_t first;
+    ay_3_891x_t second;
+
+    int16_t buffer[SOUNDBUFLEN * 2];
+    int     pos;
+} mmb_t;
+
+#endif /* _SOUND_SND_MMB_H_ */

src/include/86box/sound.h

@@ -205,6 +205,9 @@ extern const device_t ps1snd_device;
 extern const device_t ssi2001_device;
 extern const device_t entertainer_device;
 
+/* Mindscape Music Board */
+extern const device_t mmb_device;
+
 /* Pro Audio Spectrum Plus, 16, and 16D */
 extern const device_t pasplus_device;
 extern const device_t pas16_device;