diff --git a/src/engine/platform/arcade.h b/src/engine/platform/arcade.h
index 00af8f259..daa883620 100644
--- a/src/engine/platform/arcade.h
+++ b/src/engine/platform/arcade.h
@@ -30,7 +30,7 @@ class DivArcadeInterface: public ymfm::ymfm_interface {
 
 };
 
-class DivPlatformArcade: public DivPlatformOPMBase {
+class DivPlatformArcade: public DivPlatformOPM {
   protected:
     const unsigned short chanOffs[8]={
       0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07
diff --git a/src/engine/platform/fmshared_OPM.h b/src/engine/platform/fmshared_OPM.h
index c21d1c180..97844656d 100644
--- a/src/engine/platform/fmshared_OPM.h
+++ b/src/engine/platform/fmshared_OPM.h
@@ -24,7 +24,7 @@
 
 #define NOTE_LINEAR(x) (((x)<<6)+baseFreqOff+log2(parent->song.tuning/440.0)*12.0*64.0)
 
-class DivPlatformOPMBase: public DivPlatformFMBase {
+class DivPlatformOPM: public DivPlatformFMBase {
   protected:
     const unsigned char ADDR_MULT_DT=0x40;
     const unsigned char ADDR_TL=0x60;
@@ -41,7 +41,7 @@ class DivPlatformOPMBase: public DivPlatformFMBase {
       0x00, 0x08, 0x10, 0x18
     };
 
-    DivPlatformOPMBase():
+    DivPlatformOPM():
       DivPlatformFMBase() {}
 };
 
diff --git a/src/engine/platform/opl.cpp b/src/engine/platform/opl.cpp
index 43ce2f5f3..45cbd619b 100644
--- a/src/engine/platform/opl.cpp
+++ b/src/engine/platform/opl.cpp
@@ -1723,7 +1723,7 @@ void DivPlatformOPL::setFlags(unsigned int flags) {
           chipClock=3000000.0;
           break;
         case 0x04:
-          chipClock=31948800/8;
+          chipClock=38400*13*8; // 31948800/8
           break;
         case 0x05:
           chipClock=3500000.0;
diff --git a/src/engine/platform/sms.cpp b/src/engine/platform/sms.cpp
index f6624b97f..e5be23045 100644
--- a/src/engine/platform/sms.cpp
+++ b/src/engine/platform/sms.cpp
@@ -472,8 +472,12 @@ void DivPlatformSMS::setFlags(unsigned int flags) {
     case 0x0101:
       chipClock=2000000;
       break;
+    case 0x0102:
+      chipClock=COLOR_NTSC/8.0;
+      break;
   }
   resetPhase=!(flags&16);
+  divider=16;
   noiseDivider=64;
   if (sn!=NULL) delete sn;
   switch (flags&0xcc) {
@@ -524,8 +528,22 @@ void DivPlatformSMS::setFlags(unsigned int flags) {
       noiseDivider=64;
       stereo=false;
       break;
+    case 0x80: // TI SN94624
+      sn=new sn94624_device();
+      isRealSN=true;
+      noiseDivider=60;
+      stereo=false;
+      divider=2;
+      break;
+    case 0x84: // TI SN76494
+      sn=new sn76494_device();
+      isRealSN=false; // TODO
+      noiseDivider=68;
+      stereo=false;
+      divider=2;
+      break;
   }
-  rate=nuked?chipClock/16:chipClock/2;
+  rate=chipClock/divider;
   for (int i=0; i<4; i++) {
     oscBuf[i]->rate=rate;
   }
diff --git a/src/engine/platform/sms.h b/src/engine/platform/sms.h
index c4e4179fe..423995772 100644
--- a/src/engine/platform/sms.h
+++ b/src/engine/platform/sms.h
@@ -63,6 +63,7 @@ class DivPlatformSMS: public DivDispatch {
   size_t snBufLen;
   unsigned char oldValue; 
   unsigned char snNoiseMode;
+  int divider=16;
   int noiseDivider=64;
   bool updateSNMode;
   bool resetPhase;
diff --git a/src/engine/platform/sound/sn76496.cpp b/src/engine/platform/sound/sn76496.cpp
index 5062ea7a8..afb82ad3a 100644
--- a/src/engine/platform/sound/sn76496.cpp
+++ b/src/engine/platform/sound/sn76496.cpp
@@ -171,22 +171,22 @@ sn76496_base_device::sn76496_base_device(
 }
 
 sn76496_device::sn76496_device()
-	: sn76496_base_device(0x10000, 0x04, 0x08, false, false, 8, false, true)
+	: sn76496_base_device(0x10000, 0x04, 0x08, false, false, 1/*8*/, false, true)
 {
 }
 
 y2404_device::y2404_device()
-	: sn76496_base_device(0x10000, 0x04, 0x08, false, false, 8, false, true)
+	: sn76496_base_device(0x10000, 0x04, 0x08, false, false, 1/*8*/, false, true)
 {
 }
 
 sn76489_device::sn76489_device()
-	: sn76496_base_device(0x4000, 0x01, 0x02, true, false, 8, false, true)
+	: sn76496_base_device(0x4000, 0x01, 0x02, true, false, 1/*8*/, false, true)
 {
 }
 
 sn76489a_device::sn76489a_device()
-	: sn76496_base_device(0x10000, 0x04, 0x08, false, false, 8, false, true)
+	: sn76496_base_device(0x10000, 0x04, 0x08, false, false, 1/*8*/, false, true)
 {
 }
 
@@ -201,22 +201,22 @@ sn94624_device::sn94624_device()
 }
 
 ncr8496_device::ncr8496_device()
-	: sn76496_base_device(0x8000, 0x02, 0x20, true, false, 8, true, true)
+	: sn76496_base_device(0x8000, 0x02, 0x20, true, false, 1/*8*/, true, true)
 {
 }
 
 pssj3_device::pssj3_device()
-	: sn76496_base_device(0x8000, 0x02, 0x20, false, false, 8, true, true)
+	: sn76496_base_device(0x8000, 0x02, 0x20, false, false, 1/*8*/, true, true)
 {
 }
 
 gamegear_device::gamegear_device()
-	: sn76496_base_device(0x8000, 0x01, 0x08, true, true, 8, false, false)
+	: sn76496_base_device(0x8000, 0x01, 0x08, true, true, 1/*8*/, false, false)
 {
 }
 
 segapsg_device::segapsg_device()
-	: sn76496_base_device(0x8000, 0x01, 0x08, true, false, 8, false, false)
+	: sn76496_base_device(0x8000, 0x01, 0x08, true, false, 1/*8*/, false, false)
 {
 }
 
diff --git a/src/engine/platform/tx81z.h b/src/engine/platform/tx81z.h
index 16167ede4..e867416cf 100644
--- a/src/engine/platform/tx81z.h
+++ b/src/engine/platform/tx81z.h
@@ -29,7 +29,7 @@ class DivTXInterface: public ymfm::ymfm_interface {
 
 };
 
-class DivPlatformTX81Z: public DivPlatformOPMBase {
+class DivPlatformTX81Z: public DivPlatformOPM {
   protected:
     const unsigned short chanOffs[8]={
       0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07
diff --git a/src/engine/platform/ym2203.cpp b/src/engine/platform/ym2203.cpp
index 3176a1a4b..42314615b 100644
--- a/src/engine/platform/ym2203.cpp
+++ b/src/engine/platform/ym2203.cpp
@@ -1027,7 +1027,7 @@ void DivPlatformYM2203::setFlags(unsigned int flags) {
       chipClock=3000000.0;
       break;
     case 0x04:
-      chipClock=31948800/8;
+      chipClock=38400*13*8; // 31948800/8
       break;
     case 0x05:
       chipClock=3000000.0/2.0;
diff --git a/src/engine/platform/ym2608.cpp b/src/engine/platform/ym2608.cpp
index d4871486b..875f4148d 100644
--- a/src/engine/platform/ym2608.cpp
+++ b/src/engine/platform/ym2608.cpp
@@ -1400,7 +1400,7 @@ void DivPlatformYM2608::setFlags(unsigned int flags) {
       chipClock=8000000.0;
       break;
     case 0x01:
-      chipClock=31948800/4;
+      chipClock=38400*13*16; // 31948800/4
       break;
   }
   rate=fm->sample_rate(chipClock);
diff --git a/src/engine/song.h b/src/engine/song.h
index a5b68c267..6bbb00cf8 100644
--- a/src/engine/song.h
+++ b/src/engine/song.h
@@ -244,6 +244,7 @@ struct DivSong {
   //     - 0003: 1.79MHz (half NTSC)
   //     - 0100: 3MHz
   //     - 0101: 2MHz
+  //     - 0102: 447KHz (NTSC / 8)
   //   - bit 2-3, 6-7: chip type
   //     - 00: Sega VDP (16-bit noise)
   //     - 04: real SN76489 (15-bit noise)
@@ -253,6 +254,8 @@ struct DivSong {
   //     - 44: real SN76496 (17-bit noise)
   //     - 48: NCR 8496 (16-bit noise)
   //     - 4c: Tandy PSSJ-3 (16-bit noise)
+  //     - 80: real SN94624 (15-bit noise)
+  //     - 84: real SN76494 (17-bit noise)
   //   - bit 4: disable noise phase reset
   // - YM2612/YM3438:
   //   - bit 0-30: clock rate
diff --git a/src/gui/presets.cpp b/src/gui/presets.cpp
index a841f15b1..d0e63c111 100644
--- a/src/gui/presets.cpp
+++ b/src/gui/presets.cpp
@@ -1211,6 +1211,12 @@ void FurnaceGUI::initSystemPresets() {
       0
     }
   ));
+  cat.systems.push_back(FurnaceGUISysDef(
+    "TI-99/4A", {
+      DIV_SYSTEM_SMS, 64, 0, 0x182, // SN94624 447KHz
+      0
+    }
+  ));
   sysCategories.push_back(cat);
 
   cat=FurnaceGUISysCategory("Arcade systems","INSERT COIN");
diff --git a/src/gui/sysConf.cpp b/src/gui/sysConf.cpp
index e758b1798..02d06db30 100644
--- a/src/gui/sysConf.cpp
+++ b/src/gui/sysConf.cpp
@@ -69,6 +69,9 @@ void FurnaceGUI::drawSysConf(int chan, DivSystem type, unsigned int& flags, bool
       if (ImGui::RadioButton("2MHz (Sega System 1)",(flags&0xff03)==0x0101)) {
         copyOfFlags=(flags&(~0xff03))|0x0101;
       }
+      if (ImGui::RadioButton("447KHz (TI-99/4A)",(flags&0xff03)==0x0102)) {
+        copyOfFlags=(flags&(~0xff03))|0x0102;
+      }
       ImGui::Text("Chip type:");
       if (ImGui::RadioButton("Sega VDP/Master System",(flags&0xcc)==0x00)) {
         copyOfFlags=(flags&(~0xcc))|0x00;
@@ -94,6 +97,12 @@ void FurnaceGUI::drawSysConf(int chan, DivSystem type, unsigned int& flags, bool
       if (ImGui::RadioButton("Tandy PSSJ 3-voice sound",(flags&0xcc)==0x4c)) {
         copyOfFlags=(flags&(~0xcc))|0x4c;
       }
+      if (ImGui::RadioButton("TI SN94624",(flags&0xcc)==0x80)) {
+        copyOfFlags=(flags&(~0xcc))|0x80;
+      }
+      if (ImGui::RadioButton("TI SN76494",(flags&0xcc)==0x84)) {
+        copyOfFlags=(flags&(~0xcc))|0x84;
+      }
       bool noPhaseReset=flags&16;
       if (ImGui::Checkbox("Disable noise period change phase reset",&noPhaseReset)) {
         copyOfFlags=(flags&(~16))|(noPhaseReset<<4);