Sega Mega Drive/Genesis Hardware

Sega Mega Drive Motherboard revisions

Model 1

VA1 [IC BD M5 VA1]

List of IC's
IC#	Brand	Name	Description	Documentation
IC1	Signetics	SCN68000C8N64	8MHz Processor	-
IC2/IC3	Toshiba	TC51832SPL-12	CMOS 256K (32K x 8) Pseudo-SRAM, 12ns	-
IC4	SEGA	315-5308	I/O chip	-
IC5	SEGA	315-5309	I/O chip	-
IC6	Zilog	Z0840004PSC	Zilog Z80 8-bit coprocessor	-
IC7	NEC	D4168C-15-SG	64K (8,192 x 8-BIT) NMOS XRAM	-
IC8	SEGA	315-5313 (Yamaha YM7101)	VDP	-
IC9/IC10	Fujitsu	MB81461-12	Video 256K (64K x 4) DRAM	-
IC11	Yamaha	YM2612	frequency modulation synthesizer	-
IC12	Sony	CXA1034	Headphone amp	-
IC13	Sony	CXA1145	Video amp	-
IC14	NEC	UPC385C	2ch opamp (Mono output)	-
IC15	Motorola	7805CT	5v Voltage Regulator	-
IC16	Sega	315-5339 (DIP16)	I/O chip	-
IC17	Motorola	7805CT	5v Voltage Regulator

VA2 [IC BD M5 USA VA2] 837-6992

List of IC's
IC#	Brand	Name	Description	Documentation
IC1	Signetics	SCN68000C8N64	8MHz Processor	-
IC2/IC3	Toshiba	TC51832SPL-12	CMOS 256K (32K x 8-bit) Pseudo-SRAM, 12ns	-
IC4	SEGA	315-5308	I/O chip	-
IC5	SEGA	315-5309	I/O chip	-
IC6	Zilog	Z0840004PSC	Zilog Z80 8-bit coprocessor	-
IC7	NEC	D4168C-15	64K (8K x 8) NMOS XRAM, 150 ns	-
IC8	SEGA	315-5313 (Yamaha YM7101)	VDP	-
IC9/IC10	Samsung & NEC	KM424C64Z-10 & D41264V-12	256K (64K x 4-bit) VRAM & Dual-Port Graphics Buffer	-
IC11	Yamaha	YM2612	frequency modulation synthesizer (Sound Chip)	HERE
IC12	Sony	A1034(CXA1034P/M)	Headphone amp	HERE
IC13	Sony	CXA1145	Video encoder	HERE
IC14	Hitachi	HA17358	dual operational amplifier	HERE
IC15/IC17	?	7805	+5V Regulator	-
IC16	Sega	315-5345 (DIP16)	I/O chip	-

VA3 [IC BD M5 USA VA3] 837-7071

List of IC's
IC#	Brand	Name	Description	Documentation
IC1	Signetics	SCN68000C8N64	8MHz Processor	-
IC2/IC3	Toshiba	TC51832SPL-12	CMOS 256K (32K x 8) Pseudo-SRAM, 12ns	-
IC4	SEGA	315-5364	I/O chip	-
IC5	SEGA	315-5309	I/O chip	-
IC6	Zilog	Z0840004PSC	Zilog Z80 8-bit coprocessor	-
IC7	NEC	D4168C-15-SG	8,192 x 8-BIT NMOS XRAM, 150 ns	-
IC8	SEGA	315-5313	I/O chip	-
IC9/IC10	Fujitsu	MB81461-12	256K (64K x 4-bit) VRAM	-
IC11	|YM2612	frequency modulation synthesizer	-
IC12	Sony	CXA1034	Headphone amp	-
IC13	Sony	CXA1145P	RGB Encoder	-
IC14	?	LM358N	Dual Operational Amplifier	-

VA4 [IC BD M5 PAL VA4]

List of IC's
IC#	Brand	Name	Description	Documentation
IC1	Motorola	MC68000P8	8MHz Processor	-
IC2/IC3	Hitachi	HM65256BLSP-10	256Kb (32Kx8) Psuedo Static RAM, 100ns	-
IC4	SEGA	315-5364	I/O chip	-
IC5	SEGA	315-5309	I/O chip	-
IC6	Zilog	Z0840004PSC	Zilog Z80 8-bit coprocessor	-
IC7	Sanyo	LC3664RL	64Kb (8Kx8) NMOS Static RAM, 120ns	-
IC8	SEGA	315-5313	I/O chip	-
IC9/IC10	Fujitsu	MB81461-12	256K (64K x 4-bit) VRAM	-
IC11	Yamaha	YM2612	frequency modulation synthesizer	-
IC12	Sony	CXA1034P	Headphone amp	-
IC13	Sony	CXA1145P	RGB Encoder	-
IC14	Ti	LM358P	Dual Operational Amplifier	-

VA5

The only difference is the IC4 315-5402

VA6 [IC BD M5 PAL]

List of IC's
IC#	Brand	Name	Description	Documentation
IC1	Hitachi	HD68HC000P8	8MHz Processor	-
IC2/IC3	Motorola	MCM51L832ASP10	CMOS 1024 BIT SRAM	-
IC4	SEGA	315-5433	I/O chip	-
IC5	SEGA	315-5313A	I/O chip	-
IC6	Zilog	Z0840004PSC	Zilog Z80 8-bit coprocessor	-
IC7	Fujitsu	MB8464A-10LL-SK	CMOS 65,536 SRAM	-
IC8	?	?	?	-
IC9/IC10	Fujitsu	MB81461-12SL	256k 120ns Video RAM Dual Port	-
IC11	Yamaha	YM2612	Audio	-
IC12	SONY	CXA1034P	Amplifier	-
IC13	SONY	CXA1145P	Video	-
IC14	?	?	?	-

VA6 [IC BD M5 USA VA6]

List of IC's
IC#	Brand	Name	Description	Documentation
IC1	Motorola	MC68000P8	8MHz Processor	-
IC2/IC3	Motorola	MCM51L832ASP10	256Kb (32K x 8-bit) SRAM	-
IC4	SEGA	315-5433	I/O chip	-
IC5	SEGA	315-5313A	I/O chip	-
IC6	Zilog	Z0840004PSC	Zilog Z80 8-bit coprocessor	-
IC7	Samsung	KM6264BL-10	64Kb: (8K x 8-bit) SRAM	-
IC8	SEGA	315-5313	I/O chip	-
IC9/IC10	Samsung & NEC	KM424C64Z-10 & D41264V-12	256K (64K x 4-bit) VRAM & dual-port graphics buffer	-
IC11	Yamaha	YM2612	Audio	-
IC12	SONY	CXA1034P	Headphone Amplifier	-
IC13	SONY	CXA1145P	RGB Video	-
IC14	Hitachi	HA17358	Dual operational amplifier	-
IC15/17	?	7805	+5 Voltage Regulator	-

VA7 [PC BD M5 USA VA7] 171-6217-11

The VA7 is almost a Genesis 2 PCB in a Genesis 1 case. It even shares the same PCB prefix (PC).

List of IC's
IC#	Brand	Name	Description	Documentation
IC1	Motorola	MC68HC000FN8	Processor	-
IC2/IC3	Hitachi	HM65256BLFP-10T	CMOS 256K (32K x 8) High Speed Pseudo-Static RAM	HERE
IC4	Zilog	Z0840004PSC	Zilog Z80 8-bit coprocessor	-
IC5	Fujitsu	MB8464A-10L	64K (8192 words x 8 bits) Low Power SRAM	-
IC6	SEGA	315-5487-01	I/O, Bus arbiter, VDP, ym2612, TMSS	-
IC7/IC8	Hitachi	HM53461ZP-12SG	65,536-WORDx4-bit Multiport CMOS video ram	HERE
IC9/IC10	Rohm	BA10324AF	Op-amp	HERE
IC11	SONY	CXA1145M	Video	-
IC12	Toshiba	TA7805S	+5V Voltage regulator	-

List of Electrolytic Capacitors
CE#	Capacitance	Voltage
CE1	10 μF	16 V
CE2	10 μF	16 V
CE3	10 μF	16 V
CE4	10 μF	16 V
CE5	10 μF	16 V
CE6	10 μF	16 V
CE7	10 μF	16 V
CE8	10 μF	16 V
CE9	220 μF	10 V
CE10	220 μF	10 V
CE11	10 μF	16 V
CE12	220 μF	10 V
CE13	10 μF	16 V
CE14	10 μF	16 V
CE15	10 μF	16 V
CE16	220 μF	16 V
CE17	100 μF	10 V
CE18	47 μF	10 V
CE19	47 μF	10 V
CE20	10 μF	16 V
CE21	10 μF	16 V
CE22	10 μF	16 V
CE23	100 μF	10 V
CE24	47 μF	10 V
CE25	47 μF	10 V
CE26	47 μF	10 V
CE27	47 μF	10 V
CE28	47 μF	10 V
CE29	10 μF	16 V
CE30	10 μF	16 V
CE31	100 μF	10 V
Totals
17	10 μF	16 V
7	47 μF	10 V
3	100 μF	10 V
4	220 μF	10 V

Model 2

VA1 [PC BD MD2 VA1 USA]

List of IC's
IC#	Brand	Name	Description	Documentation
IC1	Motorola	MC68HC000FN8	Processor	-
IC2	Toshiba	TC511632FL-10	65,536 Word x 16 Bit Dynamic Ram	-
IC3	?	?	?	-
IC4	SEGA	315-5678 (?)	Z80 8-bit processor	-
IC5	Fujitsu	M88464A-10L	8K Words x 8-Bit (64K) CMOS SRAM Low Power	-
IC6	SEGA	315-5487, 315-5660, 315-5660-01/02, 315-5708	I/O, Bus arbiter, VDP, modified YM3438 (YM2612 compatible) FM synthesizer, TMSS. 315-5487 may have problems running in PAL mode.	-
IC7	OKI	M54C864-80	65,536-Word x 8-Bit Multiport DRAM	-
IC8	?	?	?	-
IC9/IC10	Texas Instruments, Rohm, NEC/Renesas	LM324, BA10324, C324G	Low power quad op amps	-
IC11	Sony, Samsung, Fujitsu	CXA1145M, KA2195D, MB3514	RGB Encoder (KA2195D is NTSC only)	HERE
IC12	?	?	Voltage regulator	-

VA1 [PC BD MD2 VA1 PAL]

List of IC's
IC#	Brand	Name	Description	Documentation
IC1	Motorola	MC68HC000FN8	Processor	-
IC2	Toshiba	TC511632FL-10	65,536 Word x 16 Bit Dynamic Ram	-
IC3	?	?	?	-
IC4	Toshiba	84C00AU-6	Z80 clone	-
IC5	Fujitsu	MB8464H-10LL	8K Words x 8-Bit (64K) CMOS SRAM Low Power	-
IC6	SEGA	315-5660	?	-
IC7	OKI	M54C864-80	65,536-Word x 8-Bit Multiport DRAM	-
IC8	?	?	?	-
IC9/IC10	Rohm	BA10324AF	Low power quad op amps	-
IC11	Fujitsu	MB3514	Video (RGB Encoder)	-
IC12	?	?	Voltage regulator	-

VA1 [PC BD MD2 VA1 ASIA]

List of IC's
IC#	Brand	Name	Description	Documentation
IC1	Motorola	MC68HC000FN8	Processor	-
IC2	Toshiba	TC511632FL-10	512K (32K x 16-bit) PSRAM, 100 ns	-
IC4	Toshiba	84C00AU-6	Z80 8-bit coprocessor	-
IC5	Sanyo	LC3664BML-10	64K (8Kx8-bit) SRAM	-
IC6	Sega	315-5660, 315-5660-01/02, 315-5708	I/O, Bus arbiter, VDP, modified YM3438 FM synthesizer, TMSS	-
IC7	Hitachi	HM53861J-8	512K (64K x 8-bit) VRAM	-
IC9/IC10	Texas Instruments, Rohm, NEC/Renesas	LM324, BA10324, C324G	ground sense quad op-amp	-
IC11	Fujitsu	MB3514	RGB Encoder	-
IC12			Voltage Regulator	-

VA1.8 [PC BD MD2 VA1.8 USA]

List of IC's
IC#	Brand	Name	Description	Documentation
IC1	Motorola	MC68HC000CFN8	Processor	HERE
IC2	Hitachi / Sanyo	651632DFP-15 / LC331632M-12	512K (32K x 16-bit) SRAM	-
IC3	?	?	?	-
IC4	Zilog	Z84C0006FEC	Zilog Z80 8-bit coprocessor	-
IC5	Rohm	XLJ6265AF-10SL	64K (8K x 8-bit) CMOS SRAM	-
IC6	SEGA	315-5660, 315-5660-01/02, 315-5708	I/O, Bus arbiter, VDP, modified YM3438 FM synthesizer, TMSS	-
IC7	Samsung	KM428C64J-10	512K (64K x 8-bit) VRAM	-
IC8	?	?	?	-
IC9/IC10	Rohm	BA10324AF	ground sense quad op-amp	-
IC11	Sony, Samsung, Fujitsu	CXA1145M, KA2195D, MB3514	RGB Encoder (KA2195D is NTSC only)	HERE
IC12	?	7805	+5V Voltage regulator	-

VA1.8 [PC BD MD2 VA1.8 PAL]

List of IC's
IC#	Brand	Name	Description	Documentation
IC1	Motorola	MC68HC000FN8	Processor	-
IC2	?	651632DFP-15	512K (32K x 16-bit) SRAM	-
IC3	?	?	?	-
IC4	Zilog	Z84C0006FEC	Zilog Z80 8-bit coprocessor	-
IC5	Rohm	BR6265BF-10SL	64K (8K x 8-bit) CMOS SRAM	-
IC6	SEGA	315-5660, 315-5660-01/02, 315-5708	I/O, Bus arbiter, VDP, modified YM3438 FM synthesizer, TMSS	-
IC7	Hitachi	HM53861J-8	512K (64K x 8-bit) VRAM	-
IC8	?	?	?	-
IC9/IC10	Rohm	BA10324AF	ground sense quad op-amp	-
IC11	Fujitsu	MB3514	RGB Encoder	HERE
IC12	?	7805	+5V Voltage regulator	-

VA1.8 [PC BD MD2 VA1.8 ASIA]

List of IC's
IC#	Brand	Name	Description	Documentation
IC1	Motorola	MC68HC000FN8	Processor	-
IC2	Toshiba	TC511632FL-10	512K (32K x 16-bit) PSRAM, 100 ns
IC3	?	?	?	-
IC4	Toshiba	84C00AU-6	Z80 8-bit coprocessor	-
IC5	?	?	64K (8Kx8-bit) SRAM	-
IC6	Sega	315-5660		-
IC7	Hitachi	HM53861J-8	512K (64K x 8-bit) VRAM	-
IC8	?	?	?	-
IC9/IC10	Rohm	BA10324AF	ground sense quad op-amp	-
IC11	Fujitsu	MB3514	RGB Encoder	-
IC12		7805	Voltage Regulator	-

VA2 [PC BD MD2 VA2 USA]

This revision, along with the VA2.3, uses a discrete YM2612 FM synthesizer. It is also the first Model 2 to feature the 315-5684 sound network/headphones amplifier. A small daughterboard with a 74HC14 hex-inverting schmitt trigger is typically present, its function is unknown. The BA10358 op-amplifier serves as the FM pre-amplifier.

A series resistor at R31 is responsible for the distorted PSG sound reported on these models.

List of IC's
IC#	Brand	Name	Description	Documentation
IC1	Motorola	MC68HC000FN12	Processor	-
IC2	Sanyo	LC331632M-12	512K (32768 words X 16 bits) Pseudo-SRAM
IC3	Rohm	BA10358	Dual ground sense operational amplifier	-
IC4	Zilog, Sega	Z84C0006FEC (Zilog), 315-5676 (Sega)	Zilog Z80 8-bit coprocessor	-
IC5	Sanyo, Rohm	LC3664BML-10 (Sanyo), XLJ6265AF-10SL (Rohm)	64K (8K x 8bit) CMOS SRAM	-
IC6	Sega	315-5786 (Toshiba T9N13BF)	I/O, Bus arbiter, VDP, TMSSVDP and IO chip all-in-one. Doesn't include the YM2612.	-
IC7	Samsung	KM428C64J-10	64K x 8 Bit CMOS Video RAM	-
IC8	Yamaha	YM2612	frequency modulation synthesizer	-
IC9	Sega	315-5684 (Rohm BA6166FS)	Sound Network/Headphone AMP	-
IC11	Samsung, Sony	KA2195D (Samsung), CXA1645M (Sony)	RGB Encoder	-

VA2.3 PC BD MD2 VA2.3 USA

This revision integrates the 74HC14 hex-inverting Schmitt trigger, and moves some components around. Most VA2.3s use the 315-5685 main ASIC, but some systems may use the 315-5786 alternatively. The 315-5685 ASIC has slightly broken shadow/highlight support, where the shadow/highlight effects are offset to the right by one pixel onscreen. The 315-5786 ASIC does not have this problem.

As with the VA2, a series resistor at R31 causes PSG distortion.

List of IC's
IC#	Brand	Name	Description	Documentation
IC1	Motorola	MC68000FN12	Processor	-
IC2	Toshiba	TC511632FL-10	512K (32768 words X 16 bits) Pseudo-SRAM	-
IC3	Rohm	BA10358	Dual ground sense operational amplifier	-
IC4	Zilog	Z84C0006FEC	Zilog Z80 8-bit coprocessor	-
IC5	?	XL J6265AF-10SL	4K (8K x 8-bit) CMOS SRAM	-
IC6	Sega	315-5786 (Toshiba T9N13BF) or 315-5685	VDP and IO chip all-in-one. Doesn't include the YM2612. 315-5685 ASICs have faulty shadow/highlight support.	-
IC7	Toshiba	TC5281286J-80	1M (128K x 8-bit) VRAM	-
IC8	Yamaha	YM2612	frequency modulation synthesizer	-
IC9	SEGA	315-5684 (Rohm BA6166FS)	SOUND NETWORK / HEADPHONE AMP	-
IC11	Samsung, Sony	KA2195D, CXA1645M	RGB Encoder	-
IC12	?	7805	+5V voltage regulator	-
IC13	?	74HC14	HEX SCHMITT-TRIGGER INVERTER	-

VA3 [PC BD MD2 VA3 USA HAL]

This is the first Model 2 system to utilize a smaller motherboard footprint. It is essentially a much improved VA1.8, using the 315-5684 amplifier first featured on the VA2 and VA2.3 revision motherboards. The PSG distortion problems have been fixed with this revision.

This is also the last motherboard revision to feature the NTSC-only Samsung KA2195D encoder. Early VA3 systems may use the older Sony CXA1145M encoder, while most use either the KA2195D or CXA1645M encoders.

List of IC's

IC#	Brand	Name	Description	Documentation
IC1	Motorola	MC68HC000FN8	Processor	-
IC2	Hitachi(?)	651632DFP-15	512K (32K X 16-bits) Pseudo-SRAM	-
IC3	?	?	?	-
IC4	Zilog	Z84C0006FEC	Zilog Z80 8-bit coprocessor	-
IC5	?	?	64K (8K x 8-bit) SRAM	-
IC6	Sega	315-5660, 315-5660-01/02, 315-5708, 315-5700 (FF1004)	VDP and IO chip all-in-one.	-
IC7	OKI	M54C864-80	512K (64K x 8-bit) VRAM	-
IC8	?	?	?	-
IC9	SEGA	315-5684 (Rohm BA6166FS)	SOUND NETWORK / HEADPHONE AMP	-
IC10	?	?	?	-
IC11	Sony, Samsung	CXA1145M, CXA1645M, KA2195D	RGB Encoder (KA2195D is NTSC only)	-
IC12	?	7805	+5V Voltage Regulator	-

VA4 [PC BD MD2 VA4]

Final Model 2 motherboard revision. This system features a 'Genesis-on-a-Chip' (GOAC), which integrates the VDP, FM sound source, 68000 and Z80 CPUs into one chip. First revision Model 3 systems also use this ASIC. It also uses a similar reduced motherboard footprint to the VA3 model.

Notes

Most of the time the main SEGA IC's are based on/renamed chips from other brands as follows:

• MD1 VA0, VA1, VA2, VA3, VA4, VA5, VA6, VA6.8

Yamaha YM7101 / FC1001 = Sega 315-5313 / 315-5313A / 315-5313A-01

Yamaha YM6045 / YM6045C = Sega 315-5308 / 315-5364

Yamaha YM6046 = Sega 315-5309

• MD1 VA7 & MD2 VA0, VA1, VA1.8, VA3

Yamaha FC1004 = Sega 315-5487 / 315-5487-01 / 315-5487-10 / 315-5660 / 315-5660-02 / 315-5708 / 315-5708-01

• Sega Nomad & some MD2 VA3's

Yamaha FF1004 = Sega 315-5700

• MD2 VA2, VA2.3

Toshiba T9N13BF = Sega 315-5786

Toshiba TC6158AF = Sega 315-5685. This ASIC has slightly broken shadow/highlight support.

Rohm BA6166 = Sega 315-5684

• MD2 VA4 & GEN3 VA1

Yamaha FJ3002 = Sega 315-5960

• GEN3 VA2

Yamaha FQ8007 = Sega 315-6123

See Also

• Sega Genesis
• Sega Genesis Cartridge