diff --git a/CONFIG.md b/CONFIG.md
index a4a983a5..6d492764 100644
--- a/CONFIG.md
+++ b/CONFIG.md
@@ -27,6 +27,10 @@ Since Open ROMs is highly modular, it should be possible to add other platforms
 
 If you don't know which variant to choose - select this one.
 
+### `CONFIG_BRAND_TESTING`
+
+Use this one for any kind of testing/experimental build.
+
 ### `CONFIG_BRAND_MEGA_65`, `CONFIG_BRAND_ULTIMATE_64`
 
 Select if you are using appropriate motherboard.
diff --git a/Makefile b/Makefile
index 74544f9b..b8f93f63 100644
--- a/Makefile
+++ b/Makefile
@@ -43,6 +43,7 @@ TOOLS_LIST = $(pathsubst src/tools/%,build/tools/%,$(basename $(SRC_TOOLS)))
 # List of targets
 
 STD_TARGET_LIST = build/kernal_generic.rom build/basic_generic.rom \
+                  build/kernal_testing.rom build/basic_testing.rom \
                   build/kernal_mega65.rom build/basic_mega65.rom \
                   build/kernal_ultimate64.rom build/basic_ultimate64.rom \
                   build/chargen.rom
@@ -69,7 +70,7 @@ clean:
 	@rm -rf build
 
 updatebin: $(STD_TARGET_LIST) $(TOOL_RELEASE)
-	$(TOOL_RELEASE) -i ./build -o ./bin basic_generic.rom kernal_generic.rom basic_mega65.rom kernal_mega65.rom basic_ultimate64.rom kernal_ultimate64.rom
+	$(TOOL_RELEASE) -i ./build -o ./bin basic_generic.rom kernal_generic.rom basic_testing.rom kernal_testing.rom basic_mega65.rom kernal_mega65.rom basic_ultimate64.rom kernal_ultimate64.rom
 	cp build/chargen.rom              bin/chargen.rom
 
 # Rules - tools
@@ -101,6 +102,10 @@ build/target_generic/OUTB.BIN     build/target_generic/BASIC_combined.vs: \
     $(TOOL_ASSEMBLER) $(TOOL_BUILD_SEGMENT) $(GEN_BASIC) $(SRCDIR_BASIC) \
     c64/,,config_generic.s     build/target_generic/KERNAL_combined.sym \
     $(foreach dir,$(SRCDIR_BASIC),$(wildcard $(dir)/*.s))
+build/target_testing/OUTB.BIN     build/target_generic/BASIC_combined.vs: \
+    $(TOOL_ASSEMBLER) $(TOOL_BUILD_SEGMENT) $(GEN_BASIC) $(SRCDIR_BASIC) \
+    c64/,,config_testing.s     build/target_testing/KERNAL_combined.sym \
+    $(foreach dir,$(SRCDIR_BASIC),$(wildcard $(dir)/*.s))
 build/target_mega65/OUTB.BIN      build/target_mega65/BASIC_combined.vs: \
     $(TOOL_ASSEMBLER) $(TOOL_BUILD_SEGMENT) $(GEN_BASIC)  $(SRCDIR_BASIC) \
     c64/,,config_mega65.s      build/target_mega65/KERNAL_combined.sym \
@@ -114,6 +119,10 @@ build/target_generic/OUTK.BIN     build/target_generic/KERNAL_combined.vs     bu
     $(TOOL_ASSEMBLER) $(TOOL_BUILD_SEGMENT) $(GEN_KERNAL) $(SRCDIR_KERNAL) \
     c64/,,config_generic.s \
     $(foreach dir,$(SRCDIR_KERNAL),$(wildcard $(dir)/*.s))
+build/target_testing/OUTK.BIN     build/target_testing/KERNAL_combined.vs     build/target_testing/KERNAL_combined.sym: \
+    $(TOOL_ASSEMBLER) $(TOOL_BUILD_SEGMENT) $(GEN_KERNAL) $(SRCDIR_KERNAL) \
+    c64/,,config_testing.s \
+    $(foreach dir,$(SRCDIR_KERNAL),$(wildcard $(dir)/*.s))
 build/target_mega65/OUTK.BIN      build/target_mega65/KERNAL_combined.vs      build/target_mega65/KERNAL_combined.sym: \
     $(TOOL_ASSEMBLER) $(TOOL_BUILD_SEGMENT) $(GEN_KERNAL) $(SRCDIR_KERNAL) \
     c64/,,config_mega65.s \
@@ -124,18 +133,22 @@ build/target_ultimate64/OUTK.BIN  build/target_ultimate64/KERNAL_combined.vs  bu
     $(foreach dir,$(SRCDIR_KERNAL),$(wildcard $(dir)/*.s))
 
 build/target_generic/newrom:      build/target_generic/OUTB.BIN     build/target_generic/OUTK.BIN
+build/target_testing/newrom:      build/target_testing/OUTB.BIN     build/target_testing/OUTK.BIN
 build/target_mega65/newrom:       build/target_mega65/OUTB.BIN      build/target_mega65/OUTK.BIN
 build/target_ultimate64/newrom:   build/target_ultimate64/OUTB.BIN  build/target_ultimate64/OUTK.BIN
 
 build/kernal_generic.rom:         build/target_generic/newrom
+build/kernal_testing.rom:         build/target_testing/newrom
 build/kernal_mega65.rom:          build/target_mega65/newrom
 build/kernal_ultimate64.rom:      build/target_ultimate64/newrom
 
 build/basic_generic.rom:          build/target_generic/newrom
+build/basic_testing.rom:          build/target_testing/newrom
 build/basic_mega65.rom:           build/target_mega65/newrom
 build/basic_ultimate64.rom:       build/target_ultimate64/newrom
 
 build/symbols_generic.vs:         build/target_generic/BASIC_combined.vs     build/target_generic/KERNAL_combined.vs
+build/symbols_testing.vs:         build/target_testing/BASIC_combined.vs     build/target_testing/KERNAL_combined.vs
 build/symbols_mega65.vs:          build/target_mega65/BASIC_combined.vs      build/target_mega65/KERNAL_combined.vs
 build/symbols_ultimate64.vs:      build/target_ultimate64/BASIC_combined.vs  build/target_ultimate64/KERNAL_combined.vs
 
@@ -196,7 +209,10 @@ build/newc65.rom: build/kernal_mega65.rom build/basic_mega65.rom build/chargen.r
 
 # Rules - tests
 
-.PHONY: test test_generic test_generic_x128 test_mega65 test_mega65_xemu test_ultimate64 test_hybrid test_m65 testremote testsimilarity
+.PHONY: test test_generic test_generic_x128 test_hybrid test_testing \
+        test_mega65 test_mega65_xemu test_m65 \
+        test_ultimate64 \
+        testremote testsimilarity
 
 test: test_generic
 
@@ -206,6 +222,9 @@ test_generic: build/kernal_generic.rom build/basic_generic.rom build/symbols_gen
 test_generic_x128: build/kernal_generic.rom build/basic_generic.rom build/symbols_generic.vs
 	x128 -go64 -kernal64 build/kernal_generic.rom -basic64 build/basic_generic.rom -moncommands build/symbols_generic.vs -8 empty.d64
 
+test_testing: build/kernal_testing.rom build/basic_testing.rom build/symbols_testing.vs
+	x64 -kernal build/kernal_testing.rom -basic build/basic_testing.rom -moncommands build/symbols_testing.vs -8 empty.d64
+
 test_mega65: build/kernal_mega65.rom build/basic_mega65.rom build/symbols_mega65.vs
 	x64 -kernal build/kernal_mega65.rom -basic build/basic_mega65.rom -moncommands build/symbols_mega65.vs -8 empty.d64
 
diff --git a/c64/,,config_generic.s b/c64/,,config_generic.s
index c0d78dc1..32283b0e 100644
--- a/c64/,,config_generic.s
+++ b/c64/,,config_generic.s
@@ -15,6 +15,7 @@
 #define CONFIG_PLATFORM_COMMODORE_64
 
 #define CONFIG_BRAND_GENERIC
+// #define CONFIG_BRAND_TESTING
 // #define CONFIG_BRAND_MEGA_65
 // #define CONFIG_BRAND_ULTIMATE_64
 
diff --git a/c64/,,config_mega65.s b/c64/,,config_mega65.s
index 6ffc2998..ea34f998 100644
--- a/c64/,,config_mega65.s
+++ b/c64/,,config_mega65.s
@@ -7,7 +7,6 @@
 
 // Idea:
 // - sane defaults for the Mega 65 FPGA computer
-// - enable compatibility-risky features too
 // - unless VICE gains Commodore 65 (or at least Flash8 cartridge) emulation support,
 //   do not enable CPU-specific optimizations; ROMs would be hard to test
 
@@ -17,6 +16,7 @@
 #define CONFIG_PLATFORM_COMMODORE_64
 
 // #define CONFIG_BRAND_GENERIC
+// #define CONFIG_BRAND_TESTING
 #define CONFIG_BRAND_MEGA_65
 // #define CONFIG_BRAND_ULTIMATE_64
 
@@ -31,8 +31,8 @@
 
 // Memory model configuration
 
-// #define CONFIG_MEMORY_MODEL_38K
-#define CONFIG_MEMORY_MODEL_60K
+#define CONFIG_MEMORY_MODEL_38K
+// #define CONFIG_MEMORY_MODEL_60K
 
 
 // Multiple SID support
@@ -50,11 +50,11 @@
 // Keyboard settings
 
 
-#define CONFIG_LEGACY_SCNKEY
+// #define CONFIG_LEGACY_SCNKEY
 // #define CONFIG_KEYBOARD_C128
 // #define CONFIG_KEYBOARD_C128_CAPS_LOCK
 // #define CONFIG_KEY_REPEAT_DEFAULT
-// #define CONFIG_KEY_REPEAT_ALWAYS
+#define CONFIG_KEY_REPEAT_ALWAYS
 #define CONFIG_KEY_FAST_SCAN
 #define CONFIG_JOY1_CURSOR
 #define CONFIG_JOY2_CURSOR
diff --git a/c64/,,config_testing.s b/c64/,,config_testing.s
new file mode 100644
index 00000000..c44dcef9
--- /dev/null
+++ b/c64/,,config_testing.s
@@ -0,0 +1,81 @@
+
+.const CONFIG_ID = $F0 // should be 1 byte, different for each config file!
+
+//
+// Please read CONFIG.md before modifying this file!
+//
+
+// Idea:
+// - enable compatibility-risky features
+// - enable code not normally used yto make sure it still compiles
+
+
+
+// Hardware platform and brand
+
+#define CONFIG_PLATFORM_COMMODORE_64
+
+// #define CONFIG_BRAND_GENERIC
+#define CONFIG_BRAND_TESTING
+// #define CONFIG_BRAND_MEGA_65
+// #define CONFIG_BRAND_ULTIMATE_64
+
+
+// Processor instruction set
+
+#define CONFIG_CPU_MOS_6502
+// #define CONFIG_CPU_WDC_65C02
+// #define CONFIG_CPU_CSG_65CE02
+// #define CONFIG_CPU_WDC_65816
+
+
+// Memory model configuration
+
+// #define CONFIG_MEMORY_MODEL_38K
+#define CONFIG_MEMORY_MODEL_60K
+
+
+// Multiple SID support
+
+#define CONFIG_SID_2ND
+.const CONFIG_SID_2ND_ADDRESS = $D420
+
+// #define CONFIG_SID_3RD
+.const CONFIG_SID_3RD_ADDRESS = $D440
+
+// #define CONFIG_SID_D4XX
+// #define CONFIG_SID_D5XX
+
+
+// Keyboard settings
+
+
+#define CONFIG_LEGACY_SCNKEY
+// #define CONFIG_KEYBOARD_C128
+// #define CONFIG_KEYBOARD_C128_CAPS_LOCK
+// #define CONFIG_KEY_REPEAT_DEFAULT
+// #define CONFIG_KEY_REPEAT_ALWAYS
+#define CONFIG_KEY_FAST_SCAN
+#define CONFIG_JOY1_CURSOR
+#define CONFIG_JOY2_CURSOR
+
+
+// Eye candy
+
+// #define CONFIG_BANNER_SIMPLE
+#define CONFIG_BANNER_FANCY
+// #define CONFIG_BANNER_BRAND
+// #define CONFIG_SHOW_PAL_NTSC
+
+
+// Software features
+
+#define CONFIG_PANIC_SCREEN
+#define CONFIG_DOS_WEDGE
+#define CONFIG_BCD_SAFE_INTERRUPTS
+
+
+// Debug options
+
+// #define CONFIG_DBG_STUBS_BRK
+#define CONFIG_DBG_PRINTF
diff --git a/c64/,,config_ultimate64.s b/c64/,,config_ultimate64.s
index dca7299a..fe635527 100644
--- a/c64/,,config_ultimate64.s
+++ b/c64/,,config_ultimate64.s
@@ -15,6 +15,7 @@
 #define CONFIG_PLATFORM_COMMODORE_64
 
 // #define CONFIG_BRAND_GENERIC
+// #define CONFIG_BRAND_TESTING
 // #define CONFIG_BRAND_MEGA_65
 #define CONFIG_BRAND_ULTIMATE_64
 
diff --git a/c64/aliases/,aliases_config.s b/c64/aliases/,aliases_config.s
index 77ebc752..353ec3d0 100644
--- a/c64/aliases/,aliases_config.s
+++ b/c64/aliases/,aliases_config.s
@@ -27,6 +27,9 @@
 #if CONFIG_BRAND_GENERIC
 	.eval selected++
 #endif
+#if CONFIG_BRAND_TESTING
+	.eval selected++
+#endif
 #if CONFIG_BRAND_MEGA_65
 	.eval selected++
 #endif
diff --git a/c64/basic/init/startup_banner.s b/c64/basic/init/startup_banner.s
index 5443ef47..bb0901ed 100644
--- a/c64/basic/init/startup_banner.s
+++ b/c64/basic/init/startup_banner.s
@@ -8,6 +8,8 @@
 
 #if CONFIG_BRAND_GENERIC
 	.text "OPEN ROMS GENERIC BUILD"
+#elif CONFIG_BRAND_TESTING
+	.text "OPEN ROMS TESTING BUILD"
 #elif CONFIG_BRAND_MEGA_65
 	.text "OPEN ROMS FOR MEGA65"
 #elif CONFIG_BRAND_ULTIMATE_64