C64: VC count enable seems to need to be delayed by 1 cycle after badline

- which doesn't affect normal operation
- which DOES affect VSP

BizHawk.Emulation.Cores/Computers/Commodore64/MOS/Vic.Parse.cs

@@ -101,7 +101,7 @@
 						_parseAddr &= AddressMaskEc;
 					_dataG = ReadMemory(_parseAddr);
 
-					if (!_idle)
+					if (!_idle && _vcEnable)
 					{
 						_vmli = (_vmli + 1) & 0x3F;
 						_vc = (_vc + 1) & 0x3FF;

BizHawk.Emulation.Cores/Computers/Commodore64/MOS/Vic.Registers.cs

@@ -184,19 +184,16 @@
 		
 		public void Write(int addr, int val)
 		{
-			_writtenData = val & 0xFF;
-			_writtenRegister = addr & 0x3F;
-		}
+			addr &= 0x3F;
+			val &= 0xFF;
 
-		private void DoWrite()
-		{
-			switch (_writtenRegister)
+			switch (addr)
 			{
 				case 0x17:
 					// vic-ii addendum rule 7
 					foreach (var spr in _sprites)
 					{
-						if ((_writtenData & 1) == 0 && !spr.YCrunch)
+						if ((val & 1) == 0 && !spr.YCrunch)
 						{
 							if (_parseIsSprCrunch)
 							{
@@ -207,17 +204,17 @@
 						}
 					}
 
-					WriteRegister(_writtenRegister, _writtenData);
+					WriteRegister(addr, val);
 					break;
 				case 0x19:
 					// interrupts are cleared by writing a 1
-					if ((_writtenData & 0x01) != 0)
+					if ((val & 0x01) != 0)
 						_intRaster = false;
-					if ((_writtenData & 0x02) != 0)
+					if ((val & 0x02) != 0)
 						_intSpriteDataCollision = false;
-					if ((_writtenData & 0x04) != 0)
+					if ((val & 0x04) != 0)
 						_intSpriteCollision = false;
-					if ((_writtenData & 0x08) != 0)
+					if ((val & 0x08) != 0)
 						_intLightPen = false;
 					break;
 				case 0x1E:
@@ -244,7 +241,7 @@
 					// not connected
 					break;
 				default:
-					WriteRegister(_writtenRegister, _writtenData);
+					WriteRegister(addr, val);
 					break;
 			}
 		}

BizHawk.Emulation.Cores/Computers/Commodore64/MOS/Vic.State.cs

@@ -73,13 +73,11 @@ namespace BizHawk.Emulation.Cores.Computers.Commodore64.MOS
 		private int _vblankStart;
 		private int _vc;
 		private int _vcbase;
+		private bool _vcEnable;
 		private int _vmli;
 		private int _xScroll;
 		private int _yScroll;
 
-		private int _writtenRegister;
-		private int _writtenData;
-
 		public void HardReset()
 		{
 			_backgroundColor0 = 0;
@@ -134,13 +132,11 @@ namespace BizHawk.Emulation.Cores.Computers.Commodore64.MOS
 			_spriteMulticolor1 = 0;
 			_vc = 0;
 			_vcbase = 0;
+			_vcEnable = false;
 			_vmli = 0;
 			_xScroll = 0;
 			_yScroll = 0;
 
-			_writtenRegister = -1;
-			_writtenData = 0;
-
 			// reset sprites
 			for (var i = 0; i < 8; i++)
 			{
@@ -232,10 +228,9 @@ namespace BizHawk.Emulation.Cores.Computers.Commodore64.MOS
 
 			ser.Sync(nameof(_vc), ref _vc);
 			ser.Sync(nameof(_vcbase), ref _vcbase);
+			ser.Sync(nameof(_vcEnable), ref _vcEnable);
 			ser.Sync(nameof(_videoMode), ref _videoMode);
 			ser.Sync(nameof(_vmli), ref _vmli);
-			ser.Sync(nameof(_writtenData), ref _writtenData);
-			ser.Sync(nameof(_writtenRegister), ref _writtenRegister);
 			ser.Sync(nameof(_xScroll), ref _xScroll);
 			ser.Sync(nameof(_yScroll), ref _yScroll);
 			

BizHawk.Emulation.Cores/Computers/Commodore64/MOS/Vic.cs

@@ -289,6 +289,7 @@ namespace BizHawk.Emulation.Cores.Computers.Commodore64.MOS
 			}
 
 			// badline compare
+			_vcEnable = !_idle;
 			if (_badlineEnable)
 			{
 				if ((_rasterLine & 0x7) == _yScroll)
@@ -312,12 +313,6 @@ namespace BizHawk.Emulation.Cores.Computers.Commodore64.MOS
 			ParseCycle();
 			UpdatePins();
 			Render();
-
-			if (_writtenRegister >= 0)
-			{
-				DoWrite();
-				_writtenRegister = -1;
-			}
 		}
 		
 		private void UpdateBa()