AY8910_RESISTOR_OUTPUT now selects resistance calculation by simple saturation mosfet model in ay8910.c. Currently only two drivers use this: 1942 and popeye.

src/emu/sound/ay8910.c

@@ -88,13 +88,13 @@
  *
  *  Whilst conducting, the FET operates in saturation mode:
  *
- *  Id = Kn * (Vgs - Vtn)^2
+ *  Id = Kn * (Vgs - Vth)^2
  *
  *  Using Id = Vs / RD
  *
- *  Vs = Kn * RD  * (Vg - Vs - Vtn)^2
+ *  Vs = Kn * RD  * (Vg - Vs - Vth)^2
  *
- *  finally using Vg' = Vg - Vtn
+ *  finally using Vg' = Vg - Vth
  *
  *  Vs = Vg' + 1 / (2 * Kn * RD) - sqrt((Vg' + 1 / (2 * Kn * RD))^2 - Vg'^2)
  *
@@ -386,14 +386,43 @@ static const ay8910_device::ay_ym_param ay8910_param =
  * RD was measured on a real chip to be 8m Ohm, RU was 0.8m Ohm.
  */
 
+
 static const ay8910_device::ay_ym_param ay8910_param =
 {
-	800000, 8000000,
+    800000, 8000000,
-	16,
+    16,
-	{ 15950, 15350, 15090, 14760, 14275, 13620, 12890, 11370,
+    { 15950, 15350, 15090, 14760, 14275, 13620, 12890, 11370,
-		10600,  8590,  7190,  5985,  4820,  3945,  3017,  2345 }
+        10600,  8590,  7190,  5985,  4820,  3945,  3017,  2345 }
 };
 
+static const ay8910_device::mosfet_param ay8910_mosfet_param =
+{
+    1.465385778,
+    4.9,
+    16,
+    {
+          0.00076,
+          0.80536,
+          1.13106,
+          1.65952,
+          2.42261,
+          3.60536,
+          5.34893,
+          8.96871,
+         10.97202,
+         19.32370,
+         29.01935,
+         38.82026,
+         55.50539,
+         78.44395,
+        109.49257,
+        153.72985,
+    }
+};
+
+
+
+
 /*************************************
  *
  *  Inline
@@ -492,7 +521,7 @@ INLINE void build_single_table(double rl, const ay8910_device::ay_ym_param *par,
 
 }
 
-INLINE void build_resisor_table(const ay8910_device::ay_ym_param *par, INT32 *tab, int zero_is_off)
+INLINE void build_resistor_table(const ay8910_device::ay_ym_param *par, INT32 *tab, int zero_is_off)
 {
 	int j;
 
@@ -507,6 +536,23 @@ INLINE void build_resisor_table(const ay8910_device::ay_ym_param *par, INT32 *ta
 	}
 }
 
+INLINE void build_mosfet_resistor_table(const ay8910_device::mosfet_param &par, const double rd, INT32 *tab)
+{
+    int j;
+
+    for (j=0; j < par.m_count; j++)
+    {
+        const double Vd = 5.0;
+        const double Vg = par.m_Vg - par.m_Vth;
+        const double kn = par.m_Kn[j] / 1.0e6;
+        const double p2 = 1.0 / (2.0 * kn * rd);
+        const double Vs = Vg + p2 - sqrt(p2 * p2 - Vg * Vg);
+
+        const double res = rd * ( Vd / Vs - 1.0);
+        tab[j] = res;
+    }
+}
+
 
 UINT16 ay8910_device::mix_3D()
 {
@@ -782,10 +828,13 @@ void ay8910_device::build_mixer_table()
 
 	if ((m_flags & AY8910_RESISTOR_OUTPUT) != 0)
 	{
-		for (chan=0; chan < AY8910_NUM_CHANNELS; chan++)
+	    if (m_type != PSG_TYPE_AY)
+	        fatalerror("AY8910_RESISTOR_OUTPUT currently only supported for AY8910 devices.");
+
+	    for (chan=0; chan < AY8910_NUM_CHANNELS; chan++)
 		{
-			build_resisor_table(m_par, m_vol_table[chan], m_zero_is_off);
+			build_mosfet_resistor_table(ay8910_mosfet_param, m_res_load[chan], m_vol_table[chan]);
-			build_resisor_table(m_par_env, m_env_table[chan], 0);
+			build_mosfet_resistor_table(ay8910_mosfet_param, m_res_load[chan], m_vol_table[chan]);
 		}
 	}
 	else
@@ -1075,6 +1124,7 @@ const device_type AY8910 = &device_creator<ay8910_device>;
 ay8910_device::ay8910_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock)
 	: device_t(mconfig, AY8910, "AY-3-8910A", tag, owner, clock, "ay8910", __FILE__),
 		device_sound_interface(mconfig, *this),
+        m_type(PSG_TYPE_AY),
 		m_streams(3),
 		m_ioports(2),
 		m_ready(0),
@@ -1116,6 +1166,7 @@ ay8910_device::ay8910_device(const machine_config &mconfig, device_type type, co
 							 psg_type_t psg_type, int streams, int ioports, const char *shortname, const char *source)
 	: device_t(mconfig, type, name, tag, owner, clock, shortname, source),
 		device_sound_interface(mconfig, *this),
+        m_type(psg_type),
 		m_streams(streams),
 		m_ioports(ioports),
 		m_ready(0),

src/emu/sound/ay8910.h

@@ -133,7 +133,15 @@ public:
 		int    res_count;
 		double res[32];
 	};
-	
+
+    struct mosfet_param
+    {
+        double m_Vth;
+        double m_Vg;
+        int    m_count;
+        double m_Kn[32];
+    };
+
 	void ay8910_write_ym(int addr, int data);
 	int ay8910_read_ym();
 	void ay8910_reset_ym();
@@ -154,6 +162,7 @@ private:
 	void ay8910_statesave();
 
 	// internal state
+	psg_type_t m_type;
 	int m_streams;
 	int m_ioports;
 	int m_ready;

src/mame/drivers/1942.c

@@ -84,6 +84,7 @@ static NETLIST_START(nl_1942)
 
 	SOLVER(Solver, 48000)
 	ANALOG_INPUT(V5, 5)
+    PARAM(Solver.ACCURACY, 1e-10)
 
 	/* AY 8910 internal resistors */
 
@@ -138,7 +139,9 @@ static NETLIST_START(nl_1942)
 
 	NET_C(CC6.1, VR.2)
 	NET_C(CC6.2, R1.1)
-	NET_C(R1.2, GND)
+    CAP(CC3, 220e-6)
+    NET_C(R1.2, CC3.1)
+    NET_C(CC3.2, GND)
 
 NETLIST_END()
 
@@ -549,12 +552,15 @@ static MACHINE_CONFIG_START( 1942, _1942_state )
 
 	MCFG_SOUND_ADD("ay1", AY8910, AUDIO_CLOCK)  /* 1.5 MHz */
 	MCFG_AY8910_OUTPUT_TYPE(AY8910_RESISTOR_OUTPUT)
+    MCFG_AY8910_RES_LOADS(10000.0, 10000.0, 10000.0)
 	
 	MCFG_SOUND_ROUTE_EX(0, "snd_nl", 1.0, 0)
 	MCFG_SOUND_ROUTE_EX(1, "snd_nl", 1.0, 1)
 	MCFG_SOUND_ROUTE_EX(2, "snd_nl", 1.0, 2)
+
 	MCFG_SOUND_ADD("ay2", AY8910, AUDIO_CLOCK)  /* 1.5 MHz */
 	MCFG_AY8910_OUTPUT_TYPE(AY8910_RESISTOR_OUTPUT)
+    MCFG_AY8910_RES_LOADS(10000.0, 10000.0, 10000.0)
 	
 	MCFG_SOUND_ROUTE_EX(0, "snd_nl", 1.0, 3)
 	MCFG_SOUND_ROUTE_EX(1, "snd_nl", 1.0, 4)
@@ -565,7 +571,6 @@ static MACHINE_CONFIG_START( 1942, _1942_state )
 	MCFG_SOUND_ADD("snd_nl", NETLIST_SOUND, 48000)
 	MCFG_NETLIST_SETUP(nl_1942)
 	MCFG_SOUND_ROUTE(ALL_OUTPUTS, "mono", 5.0)
-
 	MCFG_NETLIST_STREAM_INPUT("snd_nl", 0, "R_AY1_1.R")
 	MCFG_NETLIST_STREAM_INPUT("snd_nl", 1, "R_AY1_2.R")
 	MCFG_NETLIST_STREAM_INPUT("snd_nl", 2, "R_AY1_3.R")
@@ -574,6 +579,7 @@ static MACHINE_CONFIG_START( 1942, _1942_state )
 	MCFG_NETLIST_STREAM_INPUT("snd_nl", 5, "R_AY2_3.R")
 
 	MCFG_NETLIST_STREAM_OUTPUT("snd_nl", 0, "R1.1")
+	//MCFG_NETLIST_STREAM_OUTPUT("snd_nl", 0, "VR.2")
 	MCFG_NETLIST_ANALOG_MULT_OFFSET(100000.0, 0.0)
 
 MACHINE_CONFIG_END

src/mame/drivers/popeye.c

@@ -53,6 +53,7 @@ static NETLIST_START(nl_popeye)
 
 	SOLVER(Solver, 48000)
 	PARAM(Solver.ACCURACY, 1e-5)
+    PARAM(Solver.LTE,     5e-2) // Default is not enough for paddle control
 	ANALOG_INPUT(V5, 5)
 
 	/* AY 8910 internal resistors */
@@ -481,6 +482,7 @@ static MACHINE_CONFIG_DERIVED( popeye, skyskipr )
 	MCFG_SOUND_MODIFY("aysnd")
 	MCFG_SOUND_ROUTES_RESET()
 	MCFG_AY8910_OUTPUT_TYPE(AY8910_RESISTOR_OUTPUT) /* Does Sky Skipper have the same filtering? */
+    MCFG_AY8910_RES_LOADS(2000.0, 2000.0, 2000.0)
 	MCFG_AY8910_PORT_A_READ_CB(IOPORT("DSW0"))
 	MCFG_AY8910_PORT_B_WRITE_CB(WRITE8(popeye_state, popeye_portB_w))
 	MCFG_SOUND_ROUTE_EX(0, "snd_nl", 1.0, 0)