24 Jan 2018

Sega Mega-Tech & Mega-Play hack

Both systems are based on the Sega Megadrive console.
Here's a quick article about my finds on these systems.

1) Sega Mega-Tech

1.1) Cartridges
They contain 2 ROMs :
- One is the game itself. It can be a Megadrive ROM or Master System ROM.
- The second contains simply the name of the game to be displayed on the upper screen

1.2) Functionalities
Motherboard can hold up to 8 cartridges.
Player buy time rather than credits.

1.3) Compatibility
The only thing that forbids you to play Megadrive or Master System games on a Mega-Tech motherboard is the difference of pinout. With an adapter they play fine.
Region can be changed via dipswitches.

On the other side Mega-Tech games can be played on either the Megadrive or the Master System (depending of their origin) with an adapter.

2) Sega Mega-Play

2.1) Cartridges
They contain 2 ROMs :
- One is the game itself. It's a modified Megadrive ROM.
- The second contains instructions on how to play the game.

2.2) Functionalities
Motherboard can hold up to 4 cartridges.
Player buy credits.
Games are generally shorter (less levels) than their Megadrive counterparts, and harder (less lives, less time).

2.3) Compatibility
First you'll need an adapter to play Megadrive games on the Mega-Play.
However with the stock BIOS it displays an error message on the foreground:

I modified the BIOS to disable that.

Mega-Play games still plays fine with the modified BIOS so no need to swap it every time.
Region can be changed via dipswitches.

On the other side Mega-Play games can be played on the Megadrive with an adapter and a bit of hackery to disable inter-CPU exchanges and force credits.

Here's the link to Sonic The Hedgehog I've hacked to be played on the Megadrive:
It's a quick and dirty job, just leave the intro play and when level 1 starts it's up to you. Lives are almost unlimited.
Differences with the Megadrive version are:
- no Sega logo on start-up, no "Segaaaaaa" voice sample
- no select round or debug mode (present but disabled)
- game in Time Attack mode, time goes backward with for example 50s allowed to clear Green Hill Zone 1
- only 4 zones + final zone in the following order: Green Hill Zone, Spring Yard Zone, Star Light Zone, Scrap Brain Zone and Final Zone
- no bonus stage despite the fact the big ring is present, thus impossible to get chaos emeraulds
- based on the Japanese version with clouds moving on a different layer, blurry effect when in water, etc.
- high scores table present

All zones are present but some have been disabled. However you can enter them with a hack:

As they weren't meant to be playable in Time Attack mode time starts from 0 so you instantly die:

But are playable with a time hack:

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