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Mega Drive PCB revisions

From Sega Retro

Model 1

Megadrive JPN VA0 Serial No - 98M10036.jpg VA0 (JPN)
Components:
  • M68K CPU: Signetics SCN68000C8N64
  • M68K memory: 2x HM65256BLSP-15 (32Kx8 PSRAM, 150 ns)
  • Z80 CPU: Zilog Z0840004PSC
  • Z80 memory: TMM2063P - 10 (8Kx8 SRAM, 100 ns)
  • I/O chips: Sega 315-5308, Sega 315-5309, Signectic 74LS00N, 74LS161AN, 74F161AN, 74LS74AN (DIP-16)
  • VDP: Sega 315-5313 (Yamaha YM7101)
  • Video RAM: 2x HM53461ZP-12 (64Kx4 VRAM 120 ns)
  • Headphone amp: Sony CXA1034
  • Video encoder: Sony CXA1145
  • FM synthesizer: Yamaha YM2612

Due to a last-minute issue with the VDP in H40 mode, additional clock circuitry had to be added during manufacturing. This circuitry is present on a daughterboard in the center of the PCB, and contains the master oscillator (53.6931 MHz, NTSC), a 74LS74 (dual D-type flip-flops), and two 74LS161s (4-bit counter).

Megadrive VA1 Produced unit 99N83420 (JPN).JPG VA1 (JPN)
Components:
  • M68K CPU: Signetics SCN68000C8N64
  • M68K memory: 2x TC51832SPL-10 (32Kx8 PSRAM, 100 ns)
  • Z80 CPU: Zilog Z0840004PSC
  • Z80 memory: NEC D4168C-20 (8Kx8 XRAM, 200 ns)
  • I/O chips: Sega 315-5308, Sega 315-5309, Sega 315-5345 (DIP-16)
  • VDP: Sega 315-5313 (Yamaha YM7101)
  • Video RAM: 2x HM53461ZP-12 (64Kx4 VRAM 120 ns)
  • Headphone amp: Sony CXA1034
  • Video encoder: Sony CXA1145
  • FM synthesizer: Yamaha YM2612
  • Capacitors : TK Japan
MD1 IC BD M5 USA VA2.jpg VA2 (USA, High Definition Graphics)
Components:
  • M68K CPU: Signetics SCN68000C8N64
  • M68K memory: 2x TC51832SPL-12 (32Kx8 PSRAM, 120 ns)
  • Z80 CPU: Zilog Z0840004PSC
  • Z80 memory: NEC D4168C-15 (8Kx8 XRAM, 150 ns)
  • I/O chips: Sega 315-5308, Sega 315-5309, Sega 315-5345 (DIP-16)
  • VDP: Sega 315-5313 (Yamaha YM7101)
  • Video RAM: 2x [NUMBER PLEASE] (64Kx4 VRAM)
  • Headphone amp: Sony CXA1034
  • Video encoder: Sony CXA1145
  • FM synthesizer: Yamaha YM2612
Genesis 1 VA 3 Serial No - 31X21232.jpg VA3 (USA, High Definition Graphics)
Components:
  • M68K CPU: Motorola MK68000P8
  • M68K memory: 2x HM65256BL-10 (32Kx8 PSRAM, 100 ns)
  • Z80 CPU: Zilog Z0840004PSC
  • Z80 memory: KM6264BL-10 (8Kx8 SRAM, 100 ns)
  • I/O chips: Sega 315-5308, Sega 315-5309
  • VDP: Sega 315-5313 (Yamaha YM7101)
  • Video RAM: KM424C64Z-10, VKF015 (64Kx4 VRAM)
  • Headphone amp: Sony CXA1034
  • Video encoder: Sony CXA1145
  • FM synthesizer: Yamaha YM2612
  • Capacitors : Taicon, Chhsi
IC BD M5 PAL VA4.jpg VA4 (PAL)
Components:
  • M68K CPU: Motorola MC68000P8
  • M68K memory: Hitachi HM65256BLSP-10 (32Kx8 PSRAM, 100 ns)
  • I/O chip: Sega 315-5364, Sega 315-5309
  • Z80 CPU: Zilog Z0840004PSC
  • Z80 memory: Sanyo LC3664RL (8Kx8 SRAM, 120 ns)
  • VDP: Sega 315-5313 (Yamaha YM7101)
  • Video RAM: Fujitsu MB81461-12 (64Kx4 VRAM)
  • Headphone amp: Sony CXA1034P
  • Video encoder: Sony CXA1145P RGB Encoder
  • FM synthesizer: Yamaha YM2612
  • Dual Operational Amplifier: Ti LM358P
IC BD M5 JPN VA5.jpg VA5 (JPN)
IC BD M5 JPN VA6.jpg VA6 (JPN)
MD1 IC BD M5 USA VA6.jpg VA6 (USA, High Definition Graphics)
Components:
  • M68K CPU: Motorola MC68000P8
  • M68K memory: 2x HM652568LSP-10 (32Kx8 PSRAM, 100 ns)
  • Z80 CPU: Zilog Z0840004PSC
  • Z80 memory: MB8464A-10 (8Kx8 SRAM, 100 ns)
  • I/O chip: Sega 315-5433
  • VDP: Sega 315-5313 (Yamaha YM7101)
  • Video RAM: 2x [NUMBER PLEASE] (64Kx4 DRAM)
  • Headphone amp: Sony CXA1034
  • Video encoder: Sony CXA1145P
  • FM synthesizer: Yamaha YM2612
MD1 IC BD M5 PAL VA6.jpg VA6 (PAL)
VA6.8
PC BD M5 USA VA7.jpg VA7 (USA)

Model 2

PC BD MD2 VA0 PAL.jpg VA0 (PAL)
MD2 US PCB Top VA1.jpg VA1 (USA)
PC BD MD2 VA1 PAL.jpg VA1 (PAL)
Components:
  • M68K CPU: Motorola MC68HC000FN8
  • M68K memory: Sanyo LC331632M-12
  • Z80 CPU: Toshiba 84C00AU-6
  • Main ASIC: Sega 315-5660
  • Video Encoder: Fujitsu MB3514
  • Amplifier: BA10324AF
PC BD MD2 VA1.8 USA.JPG VA1.8 (USA)
Components:
  • M68K CPU: Motorola MC68HC000FN8
  • M68K memory: Sanyo LC331632M-12
  • Z80 CPU: Zilog Z84C0006FEC
  • Main ASIC: Sega 315-5660
  • Video Encoder: Samsung KA2195D
  • Amplifier: BA10324AF
PC BD MD2 VA1.8 PAL.jpg VA1.8 (PAL)
Components:
  • M68K CPU: Motorola MC68HC000FN8
  • M68K memory: ??? 651632DFP-15
  • Z80 CPU: Zilog Z84C0006FEC
  • Main ASIC: Sega 315-5660
  • Video Encoder: Fujitsu MB3514
  • Amplifier: BA10324AF
PC BD MD2 VA1.8 ASIA.jpg VA1.8 (Asia)
Components:
  • M68K CPU: Motorola MC68HC000FN8
  • M68K memory: Toshiba TC511632FL-10 (32Kx16 PSRAM, 100 ns)
  • Z80 CPU: Toshiba 84C00AU-6
  • Z80 memory: [NUMBER PLEASE] (8Kx8 SRAM)
  • Main ASIC: Sega 315-5660
PC BD MD2 VA2 USA.jpg VA2 (USA)
PC BD MD2 VA2.3 USA.jpg VA2.3 (USA)
PC BD MD2 VA3 USA HAL.JPG VA3
PC BD MD2 VA4 171 - 7229B - 11.JPG VA4
Components:
  • IC1: Sega 315-5960 ASIC
  • IC2: 32Kx16 PSRAM
  • IC3: Video RAM?
  • IC4: Sega 315-5684 audio amplifier
  • IC5: Sony CXA1645M video encoder
  • IC6: 7805 voltage regulator

This is the first Mega Drive board without any discrete CPUs. Both the 68000 and Z80 are contained with the Sega 315-5960 ASIC, as well as the VDP, YM2612, and I/O controllers.

Model 3

PC BD MD3 VA1 USA.jpg VA1 (USA)
PC BD MD3 VA2 USA.jpg VA2 (USA)
Components:
  • Main ASIC: Sega 315-6123 (contains M68K, Z80, VDP, YM2612, and probably some other components.)
  • Memory (right of main ASIC): NEC D4502161G5 (128Kx16 SDRAM)
  • Oscillator (bottom-right of main ASIC): SG53 PTR S 53.6931M
  • Video Encoder (bottom-left of main ASIC): Sony CXA1645M
  • Amplifier (left of main ASIC): TI 85AFTRF LM324