The Mega Drive / Genesis 1 has the exact same port, cable and AV pinout as the Master System 1. It also has the same pinout as the Neo Geo AES however the top left and right pins on the Neo Geo are spaced closer in than this one.

This means that a composite cable with only the bottom 5 pins will fit in the Master System / Mega Drive 1 and Neo Geo AES and all be the same identical cable. 

However, RGB cables will be different for the Master System / Mega Drive than the Neo Geo AES due to the top pin positions.

Here is the pinout looking into the console.

Hardware Overview (Sega Mega Drive)

AV Pinout (Sega Mega Drive)

Audio Circuit (Sega Mega Drive)

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BGA Reballing & Reflow

Logic Chip Families

Byte Swapping (BIOS Files)

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S-Video (Y/C)

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CleanComp Setup

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PC Floppy Drive In Amiga

Amiga Floppy Disk On PC

Gotek FlashFloppy (Amiga)

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Clone Amiga Hard Drive to PC (Amiga)

DiagROM (Amiga 500)

LHA Extractor Install (Amiga)

WHDLoad Install (Amiga)

PiStorm Emu68 Imager (Amiga)

PiStorm Flash CPLD (Amiga)

PiStorm Emu68 SD Card (Amiga)

PiStorm Emu68 Format Drives (Amiga)

HDF to Emu68 (Amiga)

Loading File on Startup (Amiga)

Creating Shortcut On Desktop (Amiga)

Amiga (Various)

Power Supply (Amiga 500)

Minimum Boot (Amiga 500)

Fat Agnus (Amiga 500)

Gary (Amiga 500)

Denise (Amiga 500)

Odd CIA (Amiga 500)

Chip RAM (Amiga 500)

Jumpers (Amiga 500)

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Power Circuit (Amiga 600)

Floppy Disc (Amiga 600)

Mouse & Joystick (Amiga 600)

No Screen (Amiga 600)

White Screen (Amiga 600)

PiStorm (Amiga 600)

Amiga 600

PiStorm Setup (Amiga 1200)

Amiga OS 3.2 Install (Amiga 1200)

Boot Diagnostics (Amiga 1200)

Solid Color Screen (Amiga 1200)

Amiga 1200

Power Up Basics (Amiga CD32)

CleanRGB Install (Amiga CD32)

DiagROM (Amiga CD32)

Amiga CD32

Basics (Macintosh SE/30)

Power / AV Pinout (Macintosh SE/30)

Minimum Boot (Macintosh SE/30)

Very Minimal Boot (Macintosh SE/30)

68k Initial Boot (Macintosh SE/30)

Initial Video Boot (Macintosh SE/30)

Apple Macintosh SE/30

Interboard Ribbon (Atari 2600)

Schematics (Atari 2600)

Hardware Overview (Atari 2600)

Joysticks (Atari 2600)

TIA Chip (Atari 2600)

Video / Button Hex Buffer (Atari 2600)

Extracting Composite Video (Atari 2600)

TIA Video Faults (Atari 2600)

Jailbars Fix (Atari 2600)

Atari 2600

Schematics (Atari 7800)

Hardare Overview (Atari 7800)

Video Output (Atari 7800)

Atari 7800

Schematics (Atari Jaguar)

Power Circuit (Atari Jaguar)

BIOS Boot (Atari Jaguar)

Black Screen (Atari Jaguar)

Red Screen Boot (Atari Jaguar)

Audio Circuit (Atari Jaguar)

Video Output (Atari Jaguar)

Tom IC (Atari Jaguar)

UART JagLink (Atari Jaguar)

50Hz /60Hz Mod (Atari Jaguar)

Region Free BIOS (Jaguar)

Atari Jaguar

Schematics (Atari Lynx)

Safe Boot (Atari Lynx)

Power Circuit (Atari Lynx)

DC Power Supply (Atari Lynx)

The Mikey ASIC (Atari Lynx)

Atari Lynx

Schematics (Atari Lynx II)

Board Scans (Atari Lynx II)

Safe Boot (Atari Lynx II)

Power Circuit (Atari Lynx II)

CleanPower Install (Atari Lynx II)

The Suzy ASIC (Atari Lynx II)

The Hayato ASIC (Atari Lynx II)

Audio Circuit (Atari Lynx II)

LCD Circuit (Atari Lynx II)

LCD Interface (Atari Lynx II)

LCD Enable Pin (Atari Lynx II)

Reading Game Cartridge (Atari Lynx II)

Hayato / Mickey / Suzy Variations (Atari Lynx II)

Game LCD Frequencies (Atari Lynx II)

Atari Lynx II

Basics (BBC Micro)

RGB Port Pinout (BBC Micro)

Boot Up Diagnostics (BBC Micro)

Drawing Graphics (BBC Micro)

Loading from Floppy (BBC Micro)

1770 Floppy Upgrade (BBC Micro)

Programming ROMs (BBC Micro)

Single Beep _ Cursor (BBC Micro)

BBC Micro

Schematics (Commodore 16)

Power Circuit (Commodore 16)

CPU 8501 (C16)

Commodore 16

Schematics (Commodore 64)

Basics (Commodore 64)

Cassette Tape (Commodore 64)

1541 Floppy (Commodore 64)

Joysticks (Commodore 64)

Commodore 64

Power Up Basics (VIC-20)

Keyboard (VIC-20)

Programmers Aid (VIC-20)

Diagnostics (VIC-20)

Commodore VIC-20

Schematics (Dreamcast)

Region Free BIOS (Dreamcast)

Region Change (Dreamcast)

Minimum Boot (Dreamcast)

GDEmu (Dreamcast)

Dreamcast

GB CleanAmp Install Guide

GB CleanPower Install Guide

Game Boy

GBP IPS Screen Install

GBP CleanAmp Install Guide

Game Boy Pocket

GBC IPS Screen Install

GBC Board Scans

GBC CleanAmp Install Guide

CleanJuice USB-C Install (Game Boy Color)

Untitled

Schematics (Game Boy Advance)

Board Scans (Game Boy Advance)

Dehum Dehiss: Removing noise from GBA audio

Power Regulator Circuit (Game Boy Advance)

Power Switch Circuit (Game Boy Advance)

Wire Free Dehum Kit (Game Boy Advance)

CleanAmp Install Guide (Game Boy Advance)

LED Triggers (Game Boy Advance)

GBA-SP Board Scans

Dehum Dehiss: Removing audio noise from GBA SP

Battery Charge Circuit (GBA SP)

Power Rails (Game Boy Advance SP)

USB-C Charging (GBA SP)

GBA-SP CleanAmp Install Guide

Game Boy Advance SP

Board Scans (Game Gear VA4/5)

Getting to Red Light Boot (Game Gear VA4)

CleanScreen V3.0 Game Gear  (VA4 VA5)

Schematics (Game Gear)

 Board Scans (Game Gear)

Hardware Overview (Game Gear)

Model Versions (Game Gear)

Soft Start / Fast Reset (Game Gear)

Getting to Red Light Boot (Game Gear)

Zombie Boot (Game Gear)

ASIC Dead Test (Game Gear)

Reading Game Cartridge (Game Gear)

LCD Circuit (Game Gear)

Visual Diagnostics (Game Gear)

Game Gear

Repair & Schematics