New (Old) 3D Golf: porting PC-9801 & Virtual Boy to Mega Drive  ⌘I  Get Info

New (Old) 3D Golf: porting PC-9801 & Virtual Boy to Mega Drive

2026-06-20<br>•  edited

7 mins read

#golf

#hacking

#japanese

#megadrive

#pc98

#reverseengineering

#romhack

#tesoft

#videogame

#virtualboy

2026-06-20

7 mins read<br>true

The Japanese Mega Drive ports of T&E SOFT’s New 3D Golf Simulation series are my favourite golf games, and recently I’ve been living inside their ROMs.

As with all the craziest ideas, it began with a “I wonder if I could”… In the early hours of one April morning I managed to pull a single course out of the game—its terrain and flyby data—and reimplement it in a viewer of my own, written in Three.js. Over the following week or so of continued reverse engineering, that viewer quietly grew into something resembling a 3D golf game running in the browser. Finding the data had some big clues: we know that there are 18 holes, the distances of each hole and their sequence order, and I’d read the courses were made of ~256 points, so adding all these heuristics together meant it was much easier to find the data than finding a needle in a haystack.

Understanding the data that well meant I could go the other way, too—back into the original Mega Drive games themselves. First I added a terrain modifier. To test it I flattened the entire course like a pancake to confirm my understanding was correct, and then cranked it up to 11 into a sort of “Hyperactive Terrain Mode” that warps the fairways into something wild. Both worked well.

An early attempt changed its mind on every run; turned out I was seeding it from an uninitialised memory location. 🤦 With no debugger console to hand, I’d been hunting bugs like this the crude way—scribbling values into the cartridge’s SRAM (its battery-backed save memory) and reading them back out, a poor man’s printf. So it wasn’t exactly straightforward.

Once that was sorted, I gave the 32-year-old game some brand new, custom user interface to match.

Next I wondered if the course data was the same across all of the four Mega Drive games, could it be the same across the games on other platforms? The answer is yes: the same course data format turns out to be used right across the series, from the original PC-9801 games (and almost certainly X68000 and FM Towns) through to the Mega Drive and even the Virtual Boy. If my (little-endian) maths is correct that’s a total of 7 unique courses, all sharing one format. There’s some reformatting that needs to be done, but the data structure is the same. And since I could already read the courses, I could write them too—patching the games to pick a course at random, or to load one that was never available on the Mega Drive in the first place. PC-9801 to Mega Drive required sorting the polygons to match how they were expected to be stored.

But I guess T&E SOFT used the same POLYSYS-CAD software to design all the courses over several years? I love how such a tool could have that sort of longevity.

That last part is the really fun bit. (Can this even be more fun?)

Here are three courses running on the Mega Drive for the first time:

T&E Selection

Extracted from the NEC PC-9801 add-on course disk:

This course is somewhat unique as it has messages spelled using coloured topology:

the 1st has “GO!” by the tee position; the 18th has “T&E” just beyond the final green

Eight Lakes G.C.

Also extracted from NEC PC-9801 add-on course disk:

A fact perhaps only I care about: during development, prior to Feb 1990, it was Seven Lakes G.C.

Seven Lakes G.C." title="Seven Lakes G.C., as seen in Comptiq Vol. 63 & Oh! PC Issue 117" loading="lazy">

Papillon C.C.

Extracted from the Nintendo Virtual Boy game T&E Virtual Golf:

It’s called Papillon—the French word for butterfly—because the course holes were laid out in the shape of a butterfly. Which was surely a nod to the shape of the Virtual Boy controller.

That last one needed a little extra work. T&E Golf on Virtual Boy doesn’t have a hole flyby, so I had to generate the camera path myself: a bezier curve from tee to pin, nudged towards the centre point of the visible course as it appears on the mini-map.

Playing these on Mega Drive is truly special and the effort was very much worthwhile.

A few things I learned along the way

Living inside the disassembly for weeks, I kept tripping over the little decisions T&E SOFT made all those years ago. Some are clever, some are quietly bonkers, and all of them made me grin:

The hole is three times too big. The cup grabs any ball within ~6.7 inches—triple a real hole’s radius—so balls drop from further out than they look. A fudge for the 320×224 screen, where ball and cup were both sub-pixel.

The polygons pre-sort themselves. No depth buffer on the Mega Drive, so the draw order is baked into the course data, back-to-front (the painter’s algorithm). The giveaway: it doesn’t match the original PC-9801 CAD order.

Backspin can reverse a putt. Spin isn’t...