diff --git a/src/target/arm7_9_common.c b/src/target/arm7_9_common.c
index af3b7b3213a155de7f421f84a7169bb55549bd4a..825f7fac82596ed44513d8dbeb236cb09ac931bd 100644
--- a/src/target/arm7_9_common.c
+++ b/src/target/arm7_9_common.c
@@ -1146,8 +1146,8 @@ int arm7_9_debug_entry(target_t *target)
 	}
 
 	/* r0 and r15 (pc) have to be restored later */
-	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 0).dirty = 1;
-	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 15).dirty = 1;
+	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 0).dirty = ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 0).valid;
+	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 15).dirty = ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 15).valid;
 
 	if ((retval = jtag->execute_queue()) != ERROR_OK)
 		return retval;
@@ -1908,7 +1908,7 @@ int arm7_9_read_memory(struct target_s *target, u32 address, u32 size, u32 count
 	}
 	
 	for (i=0; i<=last_reg; i++)
-		ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, i).dirty = 1;
+		ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, i).dirty = ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, i).valid;
 
 	arm7_9->read_xpsr(target, &cpsr, 0);
 	if ((retval = jtag_execute_queue()) != ERROR_OK)
@@ -2073,7 +2073,7 @@ int arm7_9_write_memory(struct target_s *target, u32 address, u32 size, u32 coun
 	embeddedice_store_reg(dbg_ctrl);
 	
 	for (i=0; i<=last_reg; i++)
-		ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, i).dirty = 1;
+		ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, i).dirty = ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, i).valid;
 
 	arm7_9->read_xpsr(target, &cpsr, 0);
 	if ((retval = jtag_execute_queue()) != ERROR_OK)
diff --git a/src/target/arm920t.c b/src/target/arm920t.c
index 882fec2fe3e5d3ff3e986d82db99a73cbb711214..ef95581008ea365d879dc48a236ac1af8ba2f3f2 100644
--- a/src/target/arm920t.c
+++ b/src/target/arm920t.c
@@ -989,17 +989,17 @@ int arm920t_handle_read_cache_command(struct command_context_s *cmd_ctx, char *c
 	
 	fclose(output);
 	
-	/* mark registers dirty */
-	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 0).dirty = 1;
-	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 1).dirty = 1;
-	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 2).dirty = 1;
-	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 3).dirty = 1;
-	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 4).dirty = 1;
-	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 5).dirty = 1;
-	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 6).dirty = 1;
-	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 7).dirty = 1;
-	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 8).dirty = 1;
-	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 9).dirty = 1;
+	/* mark registers dirty. */
+	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 0).dirty = ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 0).valid;
+	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 1).dirty = ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 1).valid;
+	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 2).dirty = ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 2).valid;
+	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 3).dirty = ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 3).valid;
+	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 4).dirty = ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 4).valid;
+	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 5).dirty = ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 5).valid;
+	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 6).dirty = ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 6).valid;
+	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 7).dirty = ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 7).valid;
+	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 8).dirty = ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 8).valid;
+	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 9).dirty = ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 9).valid;
 	
 	return ERROR_OK;
 }
@@ -1251,16 +1251,16 @@ int arm920t_handle_read_mmu_command(struct command_context_s *cmd_ctx, char *cmd
 	fclose(output);
 	
 	/* mark registers dirty */
-	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 0).dirty = 1;
-	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 1).dirty = 1;
-	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 2).dirty = 1;
-	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 3).dirty = 1;
-	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 4).dirty = 1;
-	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 5).dirty = 1;
-	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 6).dirty = 1;
-	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 7).dirty = 1;
-	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 8).dirty = 1;
-	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 9).dirty = 1;
+	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 0).dirty = ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 0).valid;
+	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 1).dirty = ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 1).valid;
+	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 2).dirty = ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 2).valid;
+	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 3).dirty = ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 3).valid;
+	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 4).dirty = ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 4).valid;
+	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 5).dirty = ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 5).valid;
+	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 6).dirty = ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 6).valid;
+	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 7).dirty = ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 7).valid;
+	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 8).dirty = ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 8).valid;
+	ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 9).dirty = ARMV4_5_CORE_REG_MODE(armv4_5->core_cache, armv4_5->core_mode, 9).valid;
 	
 	return ERROR_OK;
 }
diff --git a/src/target/armv7m.c b/src/target/armv7m.c
index 22ffb5e7d562895f007f0c5a9cb79e09b714aa26..8b4fd44ba1eadbbb5a948032a82cb22cb5fb97bd 100644
--- a/src/target/armv7m.c
+++ b/src/target/armv7m.c
@@ -287,7 +287,7 @@ int armv7m_write_core_reg(struct target_s *target, int num)
 	if (retval != ERROR_OK)
 	{
 		ERROR("JTAG failure");
-		armv7m->core_cache->reg_list[num].dirty = 1;
+		armv7m->core_cache->reg_list[num].dirty = armv7m->core_cache->reg_list[num].valid;
 		return ERROR_JTAG_DEVICE_ERROR;
 	}
 	DEBUG("write core reg %i value 0x%x", num , reg_value);
diff --git a/src/target/cortex_m3.c b/src/target/cortex_m3.c
index 279d986a6b9b049df9b4f584b5240be6671d059a..db9dd0547fa7e24214cc1b02cb006f62803a5edc 100644
--- a/src/target/cortex_m3.c
+++ b/src/target/cortex_m3.c
@@ -137,7 +137,7 @@ int cortex_m3_exec_opcode(target_t *target,u32 opcode, int len /* MODE, r0_inval
 	ahbap_write_system_u32(swjdp, 0x20000000, opcode);
 	ahbap_write_coreregister_u32(swjdp, 0x20000000, 15);
 	cortex_m3_single_step_core(target);
-	armv7m->core_cache->reg_list[15].dirty = 1;
+	armv7m->core_cache->reg_list[15].dirty = armv7m->core_cache->reg_list[15].valid;
 	retvalue = ahbap_write_system_atomic_u32(swjdp, 0x20000000, savedram);		
 	
 	return retvalue;
@@ -320,7 +320,7 @@ int cortex_m3_debug_entry(target_t *target)
 	/* For IT instructions xPSR must be reloaded on resume and clear on debug exec*/
 	if (xPSR & 0xf00)
 	{
-		armv7m->core_cache->reg_list[ARMV7M_xPSR].dirty = 1;
+		armv7m->core_cache->reg_list[ARMV7M_xPSR].dirty = armv7m->core_cache->reg_list[ARMV7M_xPSR].valid;
 		cortex_m3_store_core_reg_u32(target, ARMV7M_REGISTER_CORE_GP, 16, xPSR &~ 0xff);
 	}
 
@@ -1149,8 +1149,8 @@ int cortex_m3_load_core_reg_u32(struct target_s *target, enum armv7m_regtype typ
 		ahbap_write_coreregister_u32(swjdp, 0x20000000, 15);
 		cortex_m3_single_step_core(target);
 		ahbap_read_coreregister_u32(swjdp, value, 0);
-		armv7m->core_cache->reg_list[0].dirty = 1;
-		armv7m->core_cache->reg_list[15].dirty = 1;
+		armv7m->core_cache->reg_list[0].dirty = armv7m->core_cache->reg_list[0].valid;
+		armv7m->core_cache->reg_list[15].dirty = armv7m->core_cache->reg_list[15].valid;
 		ahbap_write_system_u32(swjdp, 0x20000000, savedram);
 		swjdp_transaction_endcheck(swjdp);
 		DEBUG("load from special reg %i value 0x%x", SYSm, *value);
@@ -1175,7 +1175,7 @@ int cortex_m3_store_core_reg_u32(struct target_s *target, enum armv7m_regtype ty
 		if (retval != ERROR_OK)
 		{
 			ERROR("JTAG failure %i", retval);
-			armv7m->core_cache->reg_list[num].dirty = 1;
+			armv7m->core_cache->reg_list[num].dirty = armv7m->core_cache->reg_list[num].valid;
 			return ERROR_JTAG_DEVICE_ERROR;
 		}
 		DEBUG("write core reg %i value 0x%x", num, value);
@@ -1195,7 +1195,7 @@ int cortex_m3_store_core_reg_u32(struct target_s *target, enum armv7m_regtype ty
 		ahbap_write_coreregister_u32(swjdp, 0x20000000, 15);
 		cortex_m3_single_step_core(target);
 		ahbap_write_coreregister_u32(swjdp, tempr0, 0);
-		armv7m->core_cache->reg_list[15].dirty = 1;
+		armv7m->core_cache->reg_list[15].dirty = armv7m->core_cache->reg_list[15].valid;
 		ahbap_write_system_u32(swjdp, 0x20000000, savedram);
 		swjdp_transaction_endcheck(swjdp);
 		DEBUG("write special reg %i value 0x%x ", SYSm, value);