Turtles in Time

History

Released by Konami two years after the 1989 Teenage Mutant Ninja Turtles, this sequel was praised for improving upon its predecessor in every aspect—graphics, gameplay, and music—while also being welcomed for staying faithful to the original TV animation. Unfortunately, it never received an official release in Japan. The following year it was ported to the SFC/SNES, and in the U.S., by September 1992, it became the best-selling SNES game. Most notably, it introduced the ability to throw enemies toward the screen—something fans still remember fondly. The game’s time-travel theme also made each stage unique, taking players from the prehistoric age to the Wild West and even into a futuristic city.

The Missing Chip

Although we could have had this working on the JTRIDERS core a long time ago, I had been holding it up because there is one chip on the board that is not well understood and Furrtek was working on reverse-engineering it. For me, it was important to respect his pace of work and not to release anything ahead of him that could reduce his interest.

Sadly, a few days ago Furrtek announced that he is going to retire from RE work. He may not finish this chip, so I decided to make a first implementation based on the MAME driver. At the same time, I contacted Furrtek to express our gratitude again for all his contributions and my interest in taking over this work.

The chip in question applies transformations to the sprite data, mostly applying an offset to the sprite position based on the zoom factor. These transformations would probably have been done faster by the main CPU itself, so I think they were offloaded to an external device in order to obfuscate the logic and serve as a copy-protection mechanism.

How the transformations are done is not well understood. MAME performs quite complex calculations which I think are not suitable for a small gate-array device like this chip. I have greatly simplified them to achieve practically the same (inaccurate) results, but at least they make more sense from a hardware point of view. In any case, I am not interested in fine-tuning these approximations because the preservation goal is to finish the RE work so we can have a proper implementation of the original logic.

The other chips used in the system had already been fully RE'd by Furrtek, so this one is the last piece needed for an accurate re-creation of the system.

Known Issues

Some sprites are not indexed correctly so something else is displayed. This does not affect important the gameplay much. Occasionally, music may stop. If that happens you need to reset the game. These issues are being investigated and you do not need to report them.

Coming Up on JTRIDERS

JTRiders has been a long time in beta phase, mostly because of waiting for tmnt2. However, once we added Golfing Greats to it, other games have become possible in the same core. So we will keep it in beta to add them. Premier Soccer will likely be the next addition to this core.

As the core has become larger, it does not fully fit in the small SiDi FPGA. So tmnt2 and Golfing Greats are not part of the SiDi version of the core. Golfing Greats is not part of the MiST version either. The three big FPGA systems: MiSTer, Pocket and SiDi128 can operate all supported games of this core.

Other Updates

The following games had the attract sound turned off by default. The MRA files have been updated so it is on:

• JTCPS1: captcomm, knights, kod, msword, nemo

• JTPINPON: pingpong. In this case, some DIP switches were not mapped correctly. That is fixed too.

• JTWC: gridiron