CPU clock speed emulation

apple2/ansiConsoleFrontend.go

@@ -51,12 +51,12 @@ func (fe *ansiConsoleFrontend) GetKey(strobed bool) (key uint8, ok bool) {
 		stdinReader := func(c chan uint8) {
 			reader := bufio.NewReader(os.Stdin)
 			for {
-				byte, err := reader.ReadByte()
+				key, err := reader.ReadByte()
 				if err != nil {
 					fmt.Println(err)
 					return
 				}
-				c <- byte
+				c <- key
 			}
 		}
 

apple2/apple2.go

@@ -4,22 +4,31 @@ import (
 	"bufio"
 	"go6502/core6502"
 	"os"
+	"time"
 )
 
 // Apple2 represents all the components and state of the emulated machine
 type Apple2 struct {
-	cpu        *core6502.State
-	mmu        *memoryManager
-	io         *ioC0Page
-	cg         *CharacterGenerator
-	cards      []cardBase
-	isApple2e  bool
-	panicSS    bool
-	activeSlot int // Slot that has the addressing 0xc800 to 0ccfff
+	cpu             *core6502.State
+	mmu             *memoryManager
+	io              *ioC0Page
+	cg              *CharacterGenerator
+	cards           []cardBase
+	isApple2e       bool
+	panicSS         bool
+	activeSlot      int // Slot that has the addressing 0xc800 to 0ccfff
+	commandChannel  chan int
+	cycleDurationNs float64 // Inverse of the cpu clock in Ghz
 }
 
+const (
+	// CpuClockMhz is the actual Apple II clock speed
+	CpuClockMhz     = 14.318 / 14
+	cpuClockEuroMhz = 14.238 / 14
+)
+
 // NewApple2 instantiates an apple2
-func NewApple2(romFile string, charRomFile string, panicSS bool) *Apple2 {
+func NewApple2(romFile string, charRomFile string, clockMhz float64, panicSS bool) *Apple2 {
 	var a Apple2
 	a.mmu = newMemoryManager(&a)
 	a.cpu = core6502.NewNMOS6502(a.mmu)
@@ -27,9 +36,17 @@ func NewApple2(romFile string, charRomFile string, panicSS bool) *Apple2 {
 	if charRomFile != "" {
 		a.cg = NewCharacterGenerator(charRomFile)
 	}
-	a.mmu.resetPaging()
+	a.mmu.resetRomPaging()
+	a.commandChannel = make(chan int, 100)
 	a.panicSS = panicSS
 
+	if clockMhz <= 0 {
+		// Full speed
+		a.cycleDurationNs = 0
+	} else {
+		a.cycleDurationNs = 1000.0 / clockMhz
+	}
+
 	// Set the io in 0xc000
 	a.io = newIoC0Page(&a)
 	a.mmu.setPage(0xc0, a.io)
@@ -65,18 +82,50 @@ func (a *Apple2) ConfigureStdConsole(stdinKeyboard bool, stdoutScreen bool) {
 	}
 }
 
+// SetKeyboardProvider attaches an external keyboard provider
+func (a *Apple2) SetKeyboardProvider(kb KeyboardProvider) {
+	a.io.setKeyboardProvider(kb)
+}
+
+// SendCommand enqueues a command to the emulator thread
+func (a *Apple2) SendCommand(command int) {
+	a.commandChannel <- command
+}
+
+func (a *Apple2) executeCommand(command int) {
+	//TODO
+}
+
 // Run starts the Apple2 emulation
 func (a *Apple2) Run(log bool) {
 	// Start the processor
 	a.cpu.Reset()
+	startTime := time.Now()
 	for {
+		// Run a 6502 step
 		a.cpu.ExecuteInstruction(log)
-	}
-}
 
-// SetKeyboardProvider attaches an external keyboard provider
-func (a *Apple2) SetKeyboardProvider(kb KeyboardProvider) {
-	a.io.setKeyboardProvider(kb)
+		// Execute meta commands
+		commandsPending := true
+		for commandsPending {
+			select {
+			case command := <-a.commandChannel:
+				a.executeCommand(command)
+			default:
+				commandsPending = false
+			}
+		}
+
+		if a.cycleDurationNs != 0 {
+			// Wait until next 6502 step has to run
+			clockDuration := time.Since(startTime)
+			simulatedDurationNs := time.Duration(float64(a.cpu.GetCycles()) * a.cycleDurationNs)
+			waitDuration := simulatedDurationNs - clockDuration
+			if waitDuration > 0 {
+				time.Sleep(waitDuration)
+			}
+		}
+	}
 }
 
 // LoadRom loads a binary file to the top of the memory.

apple2/memoryManager.go

@@ -98,7 +98,7 @@ func newMemoryManager(a *Apple2) *memoryManager {
 	return &mmu
 }
 
-func (mmu *memoryManager) resetPaging() {
+func (mmu *memoryManager) resetRomPaging() {
 	// Assign the first 12kb of ROM from 0xd000 to 0xfff
 	for i := 0xd0; i <= 0xff; i++ {
 		mmu.setPage(uint8(i), &(mmu.physicalROM[i-0xd0]))

apple2sdl/run.go

@@ -68,7 +68,7 @@ func SDLRun(a *apple2.Apple2) {
 			surface.Free()
 			texture.Destroy()
 		}
-		sdl.Delay(1000 / 60)
+		sdl.Delay(1000 / 30)
 	}
 
 }

core6502/execute.go

@@ -69,9 +69,15 @@ func (s *State) ExecuteInstruction(log bool) {
 // Reset resets the processor state. Moves the program counter to the vector in 0cfffc.
 func (s *State) Reset() {
 	startAddress := getWord(s.mem, vectorReset)
+	s.cycles = 0
 	s.reg.setPC(startAddress)
 }
 
+// GetCycles returns the count of CPU cycles since last reset.
+func (s *State) GetCycles() int64 {
+	return s.cycles
+}
+
 func lineString(line []uint8, opcode opcode) string {
 	t := opcode.name
 	switch opcode.addressMode {

main.go

@@ -19,6 +19,10 @@ func main() {
 		"disk",
 		"../dos33.dsk",
 		"file to load on the first disk drive")
+	cpuClock := flag.Float64(
+		"mhz",
+		apple2.CpuClockMhz,
+		"cpu speed in Mhz, use 0 for full speed")
 	charRomFile := flag.String(
 		"charRom",
 		"apple2/romdumps/Apple2rev7CharGen.rom",
@@ -42,14 +46,6 @@ func main() {
 	)
 	flag.Parse()
 
-	//romFile := "apple2/romdumps/Apple2.rom"
-	//romFile := "apple2/romdumps/Apple2_Plus.rom"
-	//romFile := "apple2/romdumps/Apple2e.rom"
-	//disk2RomFile := "apple2/romdumps/DISK2.rom"
-	//diskImage := "../dos33.dsk"
-	//diskImage := "../Apex II - Apple II Diagnostic (v4.7-1986).DSK"
-	//diskImage := "../A2Diag.v4.1.SDK"
-
 	if *dumpChars {
 		cg := apple2.NewCharacterGenerator(*charRomFile)
 		cg.Dump()
@@ -57,7 +53,7 @@ func main() {
 	}
 
 	log := false
-	a := apple2.NewApple2(*romFile, *charRomFile, *panicSS)
+	a := apple2.NewApple2(*romFile, *charRomFile, *cpuClock, *panicSS)
 	a.AddDisk2(*disk2RomFile, *diskImage)
 	if *useSdl {
 		a.ConfigureStdConsole(false, *stdoutScreen)