fixed the race condition, it works properly now

src/main/java/me/felinewith/kcpu/Kcpu.java

@@ -36,9 +36,9 @@ public class Kcpu extends BaseDevice {
 		 * 0x0000 - 0x00ff : data stack
 		 * 0x0100 - 0x017f : pc stack (return stack)
 		 * 0x0180 - 0x019f : interrupt vectors
-		 * 0x0120 : data stack pointer
-		 * 0x0122 : pc stack pointer
-		 * 0x0124 ~ unused
+		 * 0x01a0 : data stack pointer
+		 * 0x01a2 : pc stack pointer
+		 * 0x01a4 ~ unused
 		 * 0x01ff : irq state
 		 */
 		memory = new byte[0x0200];
@@ -63,7 +63,8 @@ public class Kcpu extends BaseDevice {
 		short[] regs = Arrays.copyOf(registers, registers.length);
 		short counter = pc;
 		int intq = 0;
-		if (Thread.currentThread().getId() != initThread.getId()) {
+		boolean threaded = (Thread.currentThread().getId() != initThread.getId());
+		if (threaded) {
 			logln("Starting IRQ %x : %s", irq, Thread.currentThread().getName());
 			Thread.currentThread().setUncaughtExceptionHandler(new KcpuExceptions(this, logger));
 			synchronized(memory) {
@@ -84,7 +85,26 @@ public class Kcpu extends BaseDevice {
 		}
 
 		short start = (short)((irq * 2) + 0x0180);
-		synchronized (memory) { pc = Converter.bytes2short(new byte[]{memory[start], memory[start + 1]}); }
+
+		/*
+		Here we make a backup of the CPU's internals (stacks and stack counters, mainly)
+		then wipe them clean, thus emulating the complete "clean slate" state of certain
+		processors when they enter interrupt mode
+		*/
+		byte[] memoryBackup;
+		int a;
+		synchronized (memory) {
+			// set program counter to the interrupt vector address
+			pc = Converter.bytes2short(new byte[]{memory[start], memory[start + 1]});
+
+			// make a backup of CPU memory
+			memoryBackup = Arrays.copyOf(memory, memory.length);
+
+			// now erase some key entries
+			for (a = 0; a <= 0x0180; a++) { memory[a] = 0; }
+			for (a = 0x01a0; a <= 0x01a3; a++) { memory[a] = 0; }
+		}
+
 		try {
 			while (true) {
 				workCycle(intq);
@@ -92,12 +112,24 @@ public class Kcpu extends BaseDevice {
 			}
 		}
 		catch (CPUStoppedException x) {
+			synchronized (memory) {
+				for (a = 0; a < memoryBackup.length; a++) {
+					memory[a] = memoryBackup[a];
+				}
+			}
 			logln("CPU Stopped: %s", x.getMessage());
 			//x = null;
 		}
+		synchronized (memory) {
+			for (a = 0; a < memoryBackup.length; a++) {
+				memory[a] = memoryBackup[a];
+			}
+		}
 
-		if (Thread.currentThread().getId() != initThread.getId()) {
-			registers = Arrays.copyOf(regs, regs.length);
+		if (threaded) {
+			for (a = 0; a < registers.length; a++) {
+				registers[a] = regs[a];
+			}
 			pc = counter;
 			synchronized (memory) { memory[memory.length - 1]--; }
 			initThread.notify();
@@ -177,8 +209,8 @@ public class Kcpu extends BaseDevice {
 
 		short data = ValueHelper.readShort(0, ref, registers, values, kboard);
 		synchronized (memory) {
-			short ps_c = Converter.bytes2short(new byte[]{memory[0x0122], memory[0x0123]});
-			short ps_d = Converter.bytes2short(new byte[]{memory[0x0120], memory[0x0121]});
+			short ps_c = Converter.bytes2short(new byte[]{memory[0x01a2], memory[0x01a3]});
+			short ps_d = Converter.bytes2short(new byte[]{memory[0x01a0], memory[0x01a1]});
 			short base_c = (short)(0x0100 + (ps_c * 2));
 			short base_d = (short)(ps_d * 2);
 			byte[] tmp;
@@ -211,6 +243,12 @@ public class Kcpu extends BaseDevice {
 					ps_d--;
 					break;
 			}
+			tmp = Converter.short2bytes(ps_c);
+			memory[0x01a2] = tmp[0];
+			memory[0x01a3] = tmp[1];
+			tmp = Converter.short2bytes(ps_d);
+			memory[0x01a0] = tmp[0];
+			memory[0x01a1] = tmp[1];
 		}
 
 		switch (od) {

src/main/java/me/felinewith/kcpu/memory/BootRom.java

@@ -29,7 +29,7 @@ public class BootRom extends BaseMemory {
 
 		Kasm kasm = kb.build();
 		// hardcoding some bootrom
-		//writeBytes(kasm.compileSegment("movs $0 r2"));
+		// create a device table
 		kasm.compileSegment("mark");
 		writeBytes(kasm.compileSegment("add r0 8"));
 		writeBytes(kasm.compileSegment("add r2 1"));
@@ -54,6 +54,7 @@ public class BootRom extends BaseMemory {
 		writeBytes(kasm.compileSegment("add r3 1"));
 		writeBytes(kasm.compileSegment("jdle r3 32 mark"));
 
+		// move the device table to the end of the bootrom
 		writeBytes(kasm.compileSegment("movs r0 1f00,16"));
 		writeBytes(kasm.compileSegment("mov r1 0"));
 
@@ -63,7 +64,9 @@ public class BootRom extends BaseMemory {
 		writeBytes(kasm.compileSegment("add r0 1"));
 		writeBytes(kasm.compileSegment("jdle r1 ff,16 mark"));
 
+		// lock the bootrom
 		writeBytes(kasm.compileSegment("irqm 1f00,16"));
+		writeBytes(kasm.compileSegment("irqdh 0 1"));
 
 		/*writeBytes(kasm.compileSegment("gpc"));
 		writeBytes(kasm.compileSegment("movs r0 60,16"));

src/main/java/me/felinewith/kcpu/util/helpers/MemHelper.java

 package me.felinewith.kcpu.util.helpers;
 
-import me.felinewith.kcpu.util.Converter;
 import me.felinewith.kcpu.interfaces.IMemory;
+import me.felinewith.kcpu.util.Converter;
 
 /**
  *