diff --git a/hash/arb.xml b/hash/arb.xml
index cffff250ce9..89111cb26df 100644
--- a/hash/arb.xml
+++ b/hash/arb.xml
@@ -10,9 +10,11 @@
 		<year>1980</year>
 		<publisher>AVE Micro Systems</publisher>
 		<part name="cart" interface="arb">
-			<dataarea name="rom" size="0x2000">
-				<rom name="4000-4800_ea_8332a161-1" size="0x1000" crc="00460848" sha1="ac4fe2232028bd42506a24457882296e7d3a8f54" offset="0x0000" />
-				<rom name="5000-5800_ea_8332a160-1" size="0x1000" crc="aac1dff2" sha1="9a7fc6dc98e53120e511d266304ad07f248f415a" offset="0x1000" />
+			<dataarea name="rom" size="0x8000">
+				<rom name="4000-4800_ea_8332a161-1" size="0x1000" crc="00460848" sha1="ac4fe2232028bd42506a24457882296e7d3a8f54" offset="0x4000" />
+				<rom size="0x1000" offset="0x6000" loadflag="reload" />
+				<rom name="5000-5800_ea_8332a160-1" size="0x1000" crc="aac1dff2" sha1="9a7fc6dc98e53120e511d266304ad07f248f415a" offset="0x5000" />
+				<rom size="0x1000" offset="0x7000" loadflag="reload" />
 			</dataarea>
 		</part>
 	</software>
diff --git a/src/mame/drivers/ave_arb.cpp b/src/mame/drivers/ave_arb.cpp
index 673a132ea39..f922382f714 100644
--- a/src/mame/drivers/ave_arb.cpp
+++ b/src/mame/drivers/ave_arb.cpp
@@ -104,15 +104,15 @@ DEVICE_IMAGE_LOAD_MEMBER(arb_state, cartridge)
 	m_cart->rom_alloc(size, GENERIC_ROM8_WIDTH, ENDIANNESS_LITTLE);
 	m_cart->common_load_rom(m_cart->get_rom_base(), size, "rom");
 
+	// extra ram (optional)
+	if (image.get_feature("ram"))
+		m_maincpu->space(AS_PROGRAM).install_ram(0x0800, 0x0fff, 0x1000, nullptr);
+
 	return image_init_result::PASS;
 }
 
 READ8_MEMBER(arb_state::cartridge_r)
 {
-	// range is 0x4000-0x7fff + 0xc000-0xffff
-	if (offset >= 0x8000)
-		offset -= 0x4000;
-
 	return m_cart->read_rom(offset & m_cart_mask);
 }
 
@@ -165,9 +165,10 @@ READ8_MEMBER(arb_state::input_r)
 
 void arb_state::main_map(address_map &map)
 {
-	map(0x0000, 0x07ff).mirror(0x3800).ram().share("nvram");
-	map(0x4000, 0xffff).r(FUNC(arb_state::cartridge_r)); // gap in 0x8000-0xbfff
-	map(0x8000, 0x800f).mirror(0x3ff0).rw(m_via, FUNC(via6522_device::read), FUNC(via6522_device::write));
+	// external slot is A0-A14, potential bus conflict with RAM/VIA
+	map(0x0000, 0x7fff).mirror(0x8000).r(FUNC(arb_state::cartridge_r));
+	map(0x0000, 0x07ff).mirror(0x1000).ram().share("nvram");
+	map(0x8000, 0x800f).mirror(0x1ff0).rw(m_via, FUNC(via6522_device::read), FUNC(via6522_device::write));
 }