Adding two new 8008 homebrew computers by jeng · Pull Request #13208 · mamedev/mame

jeng · 2025-01-10T11:54:15Z

The first driver is for the 8008-SBC written by Jim Loos.

The second one is for the 8008-Super written by Dr. Scott Baker.

I have uploaded the ROMS to https://github.com/jeng/homebrew-8008-mame-roms

A writeup and demos of the drivers are at Mame Master Blaster

cuavas

Please rework the code to take advantage of MAME’s framework, e.g. the memory system.

cuavas · 2025-01-23T17:36:35Z

src/mame/mame.lst

+@source:homebrew/sbc8008.cpp
+sbc8008                         // Jim Loos - 8008-SBC
+
+@source:homebrew/super8008.cpp
+super8008                       // Dr. Scott M. Baker - 8008-Super
+


Please keep this file sorted. “S” does not come after “Z”.

These should be in the correct order now.

cuavas · 2025-01-23T17:37:21Z

src/mame/layout/super8008.lay

+			<group ref="b1_leds">
+				<bounds x="0" y="345" width="10" height="47" />
+			</group>
+			<group ref="b2_leds">
+				<bounds x="7" y="345" width="10" height="47" />
+			</group>
+			<group ref="b3_leds">
+				<bounds x="14" y="345" width="10" height="47" />
+			</group>
+			<group ref="b4_leds">
+				<bounds x="21" y="345" width="10" height="47" />
+			</group>
+			<group ref="b5_leds">
+				<bounds x="28" y="345" width="10" height="47" />
+			</group>
+			<group ref="b6_leds">
+				<bounds x="35" y="345" width="10" height="47" />
+			</group>
+			<group ref="b7_leds">
+				<bounds x="42" y="345" width="10" height="47" />
+			</group>
+			<group ref="b8_leds">
+				<bounds x="49" y="345" width="10" height="47" />
+			</group>


You could use a <repeat> to make this more terse.

You should be able to use a <repeat> to generate the groups and label elements themselves to reduce copy/paste as well.

Thanks for the tip on repeat. I've made those changes.

cuavas · 2025-01-23T17:40:43Z

src/mame/layout/sbc8008.lay

+		<element name="led0" ref="orange_led">
+			<bounds x="32" y="2.5" width="5" height="5" />
+		</element>
+		<element name="led1" ref="orange_led">
+			<bounds x="37" y="2.5" width="5" height="5" />
+		</element>
+		<element name="led2" ref="orange_led">
+			<bounds x="42" y="2.5" width="5" height="5" />
+		</element>
+		<element name="led3" ref="orange_led">
+			<bounds x="47" y="2.5" width="5" height="5" />
+		</element>
+		<element name="led4" ref="orange_led">
+			<bounds x="52" y="2.5" width="5" height="5" />
+		</element>
+		<element name="led5" ref="orange_led">
+			<bounds x="57" y="2.5" width="5" height="5" />
+		</element>
+		<element name="led6" ref="orange_led">
+			<bounds x="62" y="2.5" width="5" height="5" />
+		</element>
+		<element name="led7" ref="orange_led">
+			<bounds x="67" y="2.5" width="5" height="5" />
+		</element>


You can use a <repeat> to place these LEDs.

The <repeat> has been added.

cuavas · 2025-01-23T17:41:19Z

src/mame/homebrew/super8008.cpp

+#include "cpu/i8008/i8008.h"
+#include "machine/clock.h"
+#include "machine/i8251.h"
+#include "machine/ram.h"
+#include "bus/rs232/rs232.h"
+#include "bus/super8008/super8008.h"


Please keep these sorted so they’re easier to keep track of as the list grows.

These headers are sorted now.

cuavas · 2025-01-23T17:42:01Z

src/mame/homebrew/super8008.cpp

+	// This function sets up the machine configuration
+	void super8008(machine_config &config);
+
+protected:
+	//TODO(jhe): Do we have another way to get the S0, S1 and S2 so we know when the PC has been halted?
+
+	// address maps for program memory and io memory
+	void super8008_mem(address_map &map);
+	void super8008_io(address_map &map);


Please add ATTR_COLD for cold lifecycle functions.

ATTR_COLD added to machine_start

cuavas · 2025-01-23T18:04:31Z

src/devices/bus/super8008/super8008_blaster.cpp

+void super8008_blaster_device::device_start()
+{
+	m_leds.resolve();
+}


Remember to save data members.

The m_take_state is being saved.

cuavas · 2025-01-23T18:09:43Z

src/devices/bus/super8008/super8008_blaster.cpp

+
+	RAM(config, m_ram).set_default_size("32K");


You shouldn’t be using ram_device for this – use a memory_share_creator or something.

A memory_share_creator is being used now.

cuavas · 2025-01-23T18:11:39Z

src/devices/bus/super8008/super8008_blaster.cpp

+void super8008_blaster_device::blaster_mem(address_map &map)
+{
+	map(0x0000, 0x3fff).rw(
+		FUNC(super8008_blaster_device::blaster_memory_read), 
+		FUNC(super8008_blaster_device::blaster_memory_write));
+}


Please use a memory_view to deal with swapping the RAM in and out rather than the trampoline functions. You can attach a callback to the jumper input so the view entry can be updated when it changes.

A memory_view is being used now.

cuavas · 2025-01-23T18:13:05Z

src/devices/bus/super8008/super8008.h

+	virtual void device_start() override;
+	virtual void device_reset() override;
+	virtual void device_post_load() override;


Please use ATTR_COLD for cold lifecycle members.

ATTR_COLD added to device_start

cuavas · 2025-01-23T18:13:58Z

src/devices/bus/super8008/super8008.cpp

+void super8008_bus_device::device_reset()
+{
+}
+
+void super8008_bus_device::device_post_load()
+{
+}


You don’t need to override these if you aren’t doing anything special.

I've removed these.

jeng

Thanks for the review. I think I have all of the changes made.

Also, apologies in advance about any spam from the one-off comments. I had forgotten for a minute how github worked.

jeng · 2025-04-26T16:27:20Z

src/mame/homebrew/super8008.cpp

+void super8008_state::super8008_state::ext_stat_w(offs_t offset, uint8_t data)
+{
+	switch(offset)
+	{
+		case 0: 
+			//logerror("ext_stat_w %04X  take data %02X\n", offset, data);
+			take_state = data;
+			m_bus->ext_take(data);
+			break;//take
+		case 1: 
+			//logerror("ext_stat_w %04X   int data %02X\n", offset, data);
+			m_bus->ext_int();
+			break;//int
+		case 2: 
+			//logerror("ext_stat_w %04X   req data %02X\n", offset, data);
+			m_bus->ext_req();
+			break;//req
+		case 3: 
+			//logerror("ext_stat_w %04X reset data %02X\n", offset, data);
+			m_bus->ext_reset();
+			break;//reset
+
+		default:
+			logerror("ext_stat_w INVALID %04X data %02X\n", offset, data);break;
+	}
+}


These have been moved to the address map.

jeng · 2025-04-26T16:27:34Z

src/mame/homebrew/super8008.cpp

+	uint8_t index = offset & MMAP_MASK;
+	mmap[index] = data & 0xff;
+	//logerror("super-8008 memory mapper write ($%04X) masked ($%04X) data %04X \n", offset, index, mmap[index]);


Good point about masking the uint8_t. I've removed that. I wasn't really sure how to use mirror in a way that simulates a 4x4 register.

jeng · 2025-04-26T16:27:49Z

src/mame/homebrew/super8008.cpp

+	//and bit 3 is used for issuing an external chip select.
+	map(0x0C, 0x0F).w(FUNC(super8008_state::memory_mapper_w));


I've fixed these.

jeng · 2025-04-26T16:29:15Z

src/devices/bus/super8008/super8008.cpp

+void super8008_bus_device::device_reset()
+{
+}
+
+void super8008_bus_device::device_post_load()
+{
+}


I've removed these.

jeng · 2025-04-26T16:30:51Z

src/devices/bus/super8008/super8008.h

+	virtual void device_start() override;
+	virtual void device_reset() override;
+	virtual void device_post_load() override;


ATTR_COLD added to device_start

jeng · 2025-04-26T16:40:24Z

src/devices/cpu/i8008/i8008.cpp

 	for (int addrnum = 0; addrnum < 8; addrnum++)
 		state_add(I8008_ADDR1 + addrnum, string_format("ADDR%d", addrnum + 1).c_str(), m_ADDR[addrnum].w.l).mask(0xfff);

+	state_add(I8008_STOPPED,     "STOPPED",     m_HALT);


I've removed this.

jeng · 2025-04-26T16:42:34Z

src/mame/homebrew/sbc8008.cpp

+	// This function sets up the machine configuration
+	void sbc8008(machine_config &config);
+
+protected:
+	// address maps for program memory and io memory
+	void sbc8008_mem(address_map &map);
+	void sbc8008_io(address_map &map);
+
+	required_device<cpu_device> m_maincpu;
+	required_device<ram_device> m_ram;
+	required_memory_region m_rom;
+	required_memory_bank m_rom_bank;
+	required_device<rs232_port_device> m_rs232;
+	output_finder<8> m_leds;
+	output_finder<> m_run_led;
+	output_finder<> m_txd_led;
+	output_finder<> m_rxd_led;
+
+	uint8_t bitbang_read();
+	void bitbang_write(uint8_t data);
+	uint8_t port_1_read();
+	void port_9_write(uint8_t data);
+	void port_10_write(uint8_t data);
+
+	virtual void machine_start() override;
+
+	bool start = true;
+
+	uint8_t memory_read(offs_t offset);
+	void memory_write(offs_t offset, uint8_t data);


These have been corrected.

jeng · 2025-04-26T16:43:00Z

src/mame/homebrew/sbc8008.cpp

+uint8_t sbc8008_state::memory_read(offs_t offset)
+{
+	if (start && 0 <= offset && offset < SBC8008_ROM_SIZE)
+	{			
+		return ((uint8_t*)m_rom_bank->base())[offset];
+	} 
+	else if (0 <= offset && offset < m_ram->size())
+	{
+		return m_ram->pointer()[offset];
+	} 
+	else 
+	{
+		logerror("%s:ld invalid mode read ($%02X) start %d size %d\n", 
+			machine().describe_context(), offset, start, m_ram->size());
+		return 0xff;
+	}
+}


A memory_view is being used now.

jeng · 2025-04-26T16:44:22Z

src/mame/homebrew/sbc8008.cpp

+void sbc8008_state::memory_write(offs_t offset, uint8_t data)
+{
+	if (0 <= offset && offset < m_ram->size())
+	{
+		 m_ram->pointer()[offset] = data;
+	}
+}


The custom memory_write has been removed

jeng · 2025-04-26T16:45:47Z

src/mame/homebrew/sbc8008.cpp

+uint8_t sbc8008_state::port_1_read()
+{
+	start = false;
+	return (uint8_t)start; //Is this value used in the monitor?	
+}


port_1_read is using the memory_view now to avoid side effects.

jeng added 5 commits December 28, 2024 22:26

Initial check in of the super8008 and sbc8008

7368ad2

Added range checks and fixed rom checksums

a0dcc95

Added define for the rom size and range check

f26eac3

Merge remote-tracking branch 'origin/master' into homebrew8008

0250a75

I fixed a type error gcc on windows found

d8fe7f4

cuavas reviewed Jan 23, 2025

View reviewed changes

jeng added 7 commits January 26, 2025 09:04

I added "repeats" to the layout files.

c8d6c8e

I have added a memory view to handle PoR mapping.

8e0fb8a

Changed memory access to use MAME's memory system

5c641ac

Setup memory views instead of direct rw functions.

d55e1df

I added master's output leds

bb12c48

Added LED view in headless mode

3590256

Merge remote-tracking branch 'origin/master' into homebrew8008

da26bf9

jeng commented Apr 26, 2025

View reviewed changes

		//and bit 3 is used for issuing an external chip select.
		map(0x0C, 0x0F).w(FUNC(super8008_state::memory_mapper_w));

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jeng commented Jan 10, 2025

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