Automatic fast mode while disks are spinning

apple2/apple2.go

@@ -10,17 +10,19 @@ import (
 
 // 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
-	commandChannel  chan int
-	cycleDurationNs float64 // Inverse of the cpu clock in Ghz
-	isColor         bool
+	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
+	isColor             bool
+	fastMode            bool
+	fastRequestsCounter int
 }
 
 const (
@@ -30,7 +32,8 @@ const (
 )
 
 // NewApple2 instantiates an apple2
-func NewApple2(romFile string, charRomFile string, clockMhz float64, isColor bool, panicSS bool) *Apple2 {
+func NewApple2(romFile string, charRomFile string, clockMhz float64,
+	isColor bool, fastMode bool, panicSS bool) *Apple2 {
 	var a Apple2
 	a.mmu = newMemoryManager(&a)
 	a.cpu = core6502.NewNMOS6502(a.mmu)
@@ -41,6 +44,7 @@ func NewApple2(romFile string, charRomFile string, clockMhz float64, isColor boo
 	a.mmu.resetRomPaging()
 	a.commandChannel = make(chan int, 100)
 	a.isColor = isColor
+	a.fastMode = fastMode
 	a.panicSS = panicSS
 
 	if clockMhz <= 0 {
@@ -122,6 +126,8 @@ func (a *Apple2) executeCommand(command int) {
 	}
 }
 
+const maxWaitDuration = 100 * time.Millisecond
+
 // Run starts the Apple2 emulation
 func (a *Apple2) Run(log bool) {
 	// Start the processor
@@ -142,12 +148,12 @@ func (a *Apple2) Run(log bool) {
 			}
 		}
 
-		if a.cycleDurationNs != 0 {
+		if a.cycleDurationNs != 0 && a.fastRequestsCounter <= 0 {
 			// Wait until next 6502 step has to run
 			clockDuration := time.Since(referenceTime)
 			simulatedDuration := time.Duration(float64(a.cpu.GetCycles()) * a.cycleDurationNs)
 			waitDuration := simulatedDuration - clockDuration
-			if waitDuration > 1*time.Second {
+			if waitDuration > maxWaitDuration {
 				// We have to wait too long. Let's fast forward
 				referenceTime = referenceTime.Add(-waitDuration)
 				waitDuration = 0
@@ -165,6 +171,19 @@ const (
 	apple2eRomSize = 16 * 1024
 )
 
+func (a *Apple2) requestFastMode() {
+	// Note: if the fastMode is shorter than maxWaitDuration, there won't be any gain.
+	if a.fastMode {
+		a.fastRequestsCounter++
+	}
+}
+
+func (a *Apple2) releaseFastMode() {
+	if a.fastMode {
+		a.fastRequestsCounter--
+	}
+}
+
 func (a *Apple2) loadRom(filename string) {
 	f, err := os.Open(filename)
 	if err != nil {

apple2/cardBase.go

@@ -1,6 +1,7 @@
 package apple2
 
 type cardBase struct {
+	a    *Apple2
 	rom  []memoryPage
 	slot int
 	ssr  [16]softSwitchR
@@ -8,6 +9,7 @@ type cardBase struct {
 }
 
 func (c *cardBase) insert(a *Apple2, slot int) {
+	c.a = a
 	c.slot = slot
 	if slot != 0 && c.rom[0] != nil {
 		a.mmu.setPage(uint8(0xC0+slot), c.rom[0])

apple2/cardDisk2.go

@@ -31,8 +31,6 @@ type cardDisk2Drive struct {
 	position     int
 }
 
-// type softSwitchR func(io *ioC0Page) uint8
-
 func newCardDisk2(filename string) *cardDisk2 {
 	var c cardDisk2
 	c.rom = loadCardRom(filename)
@@ -75,13 +73,19 @@ func newCardDisk2(filename string) *cardDisk2 {
 
 	// Other soft switches
 	c.ssr[0x8] = func(_ *ioC0Page) uint8 {
-		c.drive[c.selected].power = false
-		//fmt.Printf("DISKII: Disk %v is off\n", c.selected)
+		if c.drive[c.selected].power {
+			c.drive[c.selected].power = false
+			c.a.releaseFastMode()
+			//fmt.Printf("DISKII: Disk %v is off for %v\n", c.selected, x)
+		}
 		return 0
 	}
 	c.ssr[0x9] = func(_ *ioC0Page) uint8 {
-		c.drive[c.selected].power = true
-		//fmt.Printf("DISKII: Disk %v is on\n", c.selected)
+		if !c.drive[c.selected].power {
+			c.drive[c.selected].power = true
+			c.a.requestFastMode()
+			//fmt.Printf("DISKII: Disk %v is on\n", c.selected)
+		}
 		return 0
 	}
 	c.ssr[0xA] = func(_ *ioC0Page) uint8 {

apple2sdl/sdlSpeaker.go

@@ -6,8 +6,8 @@ void SpeakerCallback(void *userdata, Uint8 *stream, int len);
 */
 import "C"
 import (
+	"fmt"
 	"go6502/apple2"
-	"log"
 	"reflect"
 	"unsafe"
 
@@ -135,7 +135,7 @@ func SpeakerCallback(userdata unsafe.Pointer, stream *C.Uint8, length C.int) {
 func (s *sdlSpeaker) start() {
 	err := sdl.Init(sdl.INIT_AUDIO)
 	if err != nil {
-		log.Printf("Error starting SDL audio: %v.\n", err)
+		fmt.Printf("Error starting SDL audio: %v.\n", err)
 		return
 	}
 
@@ -148,7 +148,7 @@ func (s *sdlSpeaker) start() {
 	}
 
 	if err := sdl.OpenAudio(spec, nil); err != nil {
-		log.Printf("Error opening the SDL audio channel: %v.\n", err)
+		fmt.Printf("Error opening the SDL audio channel: %v.\n", err)
 		return
 	}
 	sdl.PauseAudio(false)

main.go

@@ -44,6 +44,12 @@ func main() {
 		false,
 		"emulate a green phosphor monitor instead of a NTSC color TV. Use F6 to toggle.",
 	)
+	fastDisk := flag.Bool(
+		"fastDisk",
+		true,
+		"set fast mode when the disks are spinning",
+	)
+
 	panicSS := flag.Bool(
 		"panicss",
 		false,
@@ -62,7 +68,7 @@ func main() {
 	}
 
 	log := false
-	a := apple2.NewApple2(*romFile, *charRomFile, *cpuClock, !*mono, *panicSS)
+	a := apple2.NewApple2(*romFile, *charRomFile, *cpuClock, !*mono, *fastDisk, *panicSS)
 	if *disk2Slot > 0 {
 		a.AddDisk2(*disk2Slot, *disk2RomFile, *diskImage)
 	}