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[#314] zx-spectrum: Speedup device timings
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@vbmacher
vbmacher committed May 18, 2023
1 parent 1097cf7 commit 4da1871
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Showing 4 changed files with 160 additions and 64 deletions.
152 changes: 114 additions & 38 deletions ...trum-bus/src/main/java/net/emustudio/plugins/device/zxspectrum/bus/ZxSpectrumBusImpl.java
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@
*/
package net.emustudio.plugins.device.zxspectrum.bus;

import net.emustudio.emulib.plugins.cpu.CPUContext;
import net.emustudio.emulib.plugins.cpu.TimedEventsProcessor;
import net.emustudio.emulib.plugins.memory.AbstractMemoryContext;
import net.emustudio.emulib.plugins.memory.MemoryContext;
Expand All @@ -27,15 +28,17 @@
import net.emustudio.plugins.device.zxspectrum.bus.api.ZxSpectrumBus;
import net.jcip.annotations.NotThreadSafe;

import java.util.*;
import java.util.function.Consumer;
import java.util.HashMap;
import java.util.Map;
import java.util.Objects;
import java.util.Optional;

/**
* ZX Spectrum bus (for 48K ZX spectrum).
* <p>
* Adds memory & I/O port contention.
* <p>
* https://sinclair.wiki.zxnet.co.uk/wiki/Contended_memory#Timing_differences
* <a href="https://sinclair.wiki.zxnet.co.uk/wiki/Contended_memory#Timing_differences">ZX Spectrum48 timing</a>
* On the 16K and 48K models of ZX Spectrum, the memory from 0x4000 to 0x7fff is contended. If the contended
* memory is accessed 14335[2] or 14336 tstates after an interrupt (see the timing differences section below
* for information on the 14335/14336 issue), the Z80 will be delayed for 6 tstates. After 14336 tstates,
Expand Down Expand Up @@ -76,37 +79,56 @@
* Yes | Set | C:1, C:1, C:1, C:1
*/
@NotThreadSafe
public class ZxSpectrumBusImpl extends AbstractMemoryContext<Byte> implements ZxSpectrumBus {
private final static int SCREEN_LINES = 192;
private final static int CONTENTION_TSTATE_START = 14335;
private static final int CPU_INTERRUPT_TSTATES = 69888;
public class ZxSpectrumBusImpl extends AbstractMemoryContext<Byte> implements ZxSpectrumBus, CPUContext.PassedCyclesListener {
private static final long LINE_TSTATES = 224;

// from 14335 to 14463, then 96 tstates pause to reach "end of line", then repeat.
private final static Map<Long, Integer> CONTENTION_MAP = new HashMap<>();

static {
CONTENTION_MAP.put(14335L, 6);
CONTENTION_MAP.put(14336L, 5);
CONTENTION_MAP.put(14337L, 4);
CONTENTION_MAP.put(14338L, 3);
CONTENTION_MAP.put(14339L, 2);
CONTENTION_MAP.put(14340L, 1);
CONTENTION_MAP.put(14343L, 6);
CONTENTION_MAP.put(14344L, 5);
CONTENTION_MAP.put(14345L, 4);
CONTENTION_MAP.put(14346L, 3);
CONTENTION_MAP.put(14347L, 2);
CONTENTION_MAP.put(14348L, 1);
CONTENTION_MAP.put(14351L, 6);
CONTENTION_MAP.put(14352L, 5);
CONTENTION_MAP.put(14353L, 4);
CONTENTION_MAP.put(14354L, 3);
CONTENTION_MAP.put(14355L, 2);
CONTENTION_MAP.put(14356L, 1);
CONTENTION_MAP.put(14359L, 6);
CONTENTION_MAP.put(14360L, 5);
CONTENTION_MAP.put(14361L, 4);
CONTENTION_MAP.put(14362L, 3);
CONTENTION_MAP.put(14363L, 2);
// CONTENTION_MAP.put(14364L, 1);
}

private ContextZ80 cpu;
private MemoryContext<Byte> memory;
private volatile byte busData; // data on the bus
private TimedEventsProcessor tep;
private boolean isContended = false;

private long contentionCycles;

private final Map<Integer, Context8080.CpuPortDevice> deferredAttachments = new HashMap<>();

public void initialize(ContextZ80 cpu, MemoryContext<Byte> memory) {
this.cpu = Objects.requireNonNull(cpu);
this.memory = Objects.requireNonNull(memory);
this.tep = cpu.getTimedEventsProcessor().orElseThrow(() -> new RuntimeException("CPU must provide TimedEventProcessor"));

for (Map.Entry<Integer, Context8080.CpuPortDevice> attachment : deferredAttachments.entrySet()) {
if (!cpu.attachDevice(attachment.getKey(), new ContendedDeviceProxy(attachment.getValue()))) {
throw new RuntimeException("Could not attach device " + attachment.getValue().getName() + " to CPU");
}
}

// 17 x from 14335 to 14463, then 96 tstates pause to reach "end of line", then repeat.
// the t-state 14335 is the first screen line to be read.
int cycles = CONTENTION_TSTATE_START + CPU_INTERRUPT_TSTATES;
for (int line = 0; line < SCREEN_LINES; line++) {
scheduleMemoryContention(cycles);
cycles = cycles + 17 * 8 + 96 - 1;
}
}


Expand Down Expand Up @@ -147,6 +169,16 @@ public void writeMemoryNotContended(int location, byte data) {
memory.write(location, data);
}

@Override
public void addPassedCyclesListener(CPUContext.PassedCyclesListener passedCyclesListener) {
cpu.addPassedCyclesListener(passedCyclesListener);
}

@Override
public void removePassedCyclesListener(CPUContext.PassedCyclesListener passedCyclesListener) {
cpu.removePassedCyclesListener(passedCyclesListener);
}

@Override
public Byte readData() {
return busData;
Expand All @@ -159,25 +191,25 @@ public void writeData(Byte data) {

@Override
public Byte read(int location) {
setContended(location);
contendedMemory(location);
return memory.read(location);
}

@Override
public Byte[] read(int location, int count) {
setContended(location);
contendedMemory(location);
return memory.read(location, count);
}

@Override
public void write(int location, Byte data) {
setContended(location);
contendedMemory(location);
memory.write(location, data);
}

@Override
public void write(int location, Byte[] data, int count) {
setContended(location);
contendedMemory(location);
memory.write(location, data, count);
}

Expand Down Expand Up @@ -206,25 +238,71 @@ public MemoryContextAnnotations annotations() {
return memory.annotations();
}

private void setContended(int location) {
this.isContended = location >= 0x4000 && location <= 0x7FFF;
private void contendedMemory(int location) {
if (location >= 0x4000 && location <= 0x7FFF) {
Integer cycles = CONTENTION_MAP.get(contentionCycles);
if (cycles != null) {
cpu.addCycles(cycles);
}
}
}

private void scheduleMemoryContention(int startCycles) {
// 17 x from 14335 to 14463, then 96 tstates pause to reach "end of line", then repeat.
Runnable slowDownByOneCycle = () -> {
if (isContended) {
cpu.addCycles(1);
private void contendedPort(int portAddress) {
// High byte | |
// in 40 - 7F? | Low bit | Contention pattern
// ------------+---------+-------------------
// No | Reset | N:1, C:3
// No | Set | N:4
// Yes | Reset | C:1, C:3
// Yes | Set | C:1, C:1, C:1, C:1

if (portAddress >= 0x4000 && portAddress <= 0x7FFF) {
// after this, CPU adds 4 cycles for I/O.
if ((portAddress & 1) == 0) {
// Yes | Reset | C:1, C:3
Integer cycles = CONTENTION_MAP.get(contentionCycles); // at C:1
if (cycles != null) {
cpu.addCycles(cycles);
}
cycles = CONTENTION_MAP.get(contentionCycles + 1); // after C:1
if (cycles != null) {
cpu.addCycles(cycles);
}
} else {
// Yes | Set | C:1, C:1, C:1, C:1
Integer cycles = CONTENTION_MAP.get(contentionCycles); // at C:1
if (cycles != null) {
cpu.addCycles(cycles);
}
cycles = CONTENTION_MAP.get(contentionCycles + 1); // 2x at C:1
if (cycles != null) {
cpu.addCycles(cycles);
}
cycles = CONTENTION_MAP.get(contentionCycles + 2); // 3x at C:1
if (cycles != null) {
cpu.addCycles(cycles);
}
cycles = CONTENTION_MAP.get(contentionCycles + 3); // after 3x at C:1
if (cycles != null) {
cpu.addCycles(cycles);
}
}
};

for (int i = 0; i < 17; i++) {
for (int j = 0; j < 6; j++) {
tep.schedule(startCycles + i * 8 + j, slowDownByOneCycle);
} else {
// No | Reset | N:1, C:3
if ((portAddress & 1) == 0) {
Integer cycles = CONTENTION_MAP.get(contentionCycles + 1); // after N:1
if (cycles != null) {
cpu.addCycles(cycles);
}
}
}
}

@Override
public void passedCycles(long tstates) {
contentionCycles = (contentionCycles + tstates) % (LINE_TSTATES + 14335);
}

private class ContendedDeviceProxy implements Context8080.CpuPortDevice {
private final Context8080.CpuPortDevice device;

Expand All @@ -234,15 +312,13 @@ private ContendedDeviceProxy(Context8080.CpuPortDevice device) {

@Override
public byte read(int portAddress) {
setContended(portAddress);
// TODO: portAddress & 1 == 0 ==> contended for 3 cycles only
contendedPort(portAddress);
return device.read(portAddress);
}

@Override
public void write(int portAddress, byte data) {
setContended(portAddress);
// TODO: portAddress & 1 == 0 ==> contended for 3 cycles only
contendedPort(portAddress);
device.write(portAddress, data);
}

Expand Down
5 changes: 5 additions & 0 deletions ...trum-bus/src/main/java/net/emustudio/plugins/device/zxspectrum/bus/api/ZxSpectrumBus.java
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Expand Up @@ -19,6 +19,7 @@
package net.emustudio.plugins.device.zxspectrum.bus.api;

import net.emustudio.emulib.plugins.annotations.PluginContext;
import net.emustudio.emulib.plugins.cpu.CPUContext;
import net.emustudio.emulib.plugins.cpu.TimedEventsProcessor;
import net.emustudio.emulib.plugins.device.DeviceContext;
import net.emustudio.emulib.plugins.memory.MemoryContext;
Expand Down Expand Up @@ -86,4 +87,8 @@ public interface ZxSpectrumBus extends DeviceContext<Byte>, MemoryContext<Byte>
* @param data data to write
*/
void writeMemoryNotContended(int location, byte data);

void addPassedCyclesListener(CPUContext.PassedCyclesListener passedCyclesListener);

void removePassedCyclesListener(CPUContext.PassedCyclesListener passedCyclesListener);
}
12 changes: 4 additions & 8 deletions .../device/zxspectrum-ula/src/main/java/net/emustudio/plugins/device/zxspectrum/ula/ULA.java
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Expand Up @@ -18,14 +18,12 @@
*/
package net.emustudio.plugins.device.zxspectrum.ula;

import net.emustudio.emulib.plugins.cpu.TimedEventsProcessor;
import net.emustudio.plugins.cpu.intel8080.api.Context8080;
import net.emustudio.plugins.device.zxspectrum.bus.api.ZxSpectrumBus;
import net.emustudio.plugins.device.zxspectrum.ula.gui.Keyboard;

import java.awt.event.KeyEvent;
import java.util.Arrays;
import java.util.NoSuchElementException;
import java.util.Objects;

/**
Expand Down Expand Up @@ -119,12 +117,6 @@ public void triggerInterrupt() {
bus.signalInterrupt(RST_7);
}

public TimedEventsProcessor getTimedEventsProcessor() {
return bus
.getTimedEventsProcessor()
.orElseThrow(() -> new NoSuchElementException("The CPU does not provide TimedEventProcessor"));
}

public void readLine(int y) {
for (int x = 0; x < SCREEN_WIDTH; x++) {
videoMemory[x][y] = bus.readMemoryNotContended(0x4000 + lineStartOffsets[y] + x);
Expand All @@ -140,6 +132,10 @@ public int getBorderColor() {
return borderColor;
}

public ZxSpectrumBus getBus() {
return bus;
}

@Override
public byte read(int portAddress) {
// A zero in one of the five lowest bits means that the corresponding key is pressed.
Expand Down
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